Maxim MAX11802EWC+T Low-power, ultra-small resistive touch-screen controllers with i2c/spi interface Datasheet

19-4711; Rev 0; 7/09
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
The MAX11800–MAX11803 low-power touch-screen controllers operate from a single supply of 1.70V to 3.6V, targeting power-sensitive applications such as handheld
equipment. The devices contain a 12-bit SAR ADC and a
multiplexer to interface with a resistive touch-screen
panel. A digital serial interface provides communications.
The MAX11800–MAX11803 include digital preprocessing
of the touch-screen measurements, reducing bus loading
and application-processor resource requirements. The
included smart interrupt function generator greatly
reduces the frequency of interrupt servicing to the
devices. The MAX11800–MAX11803 enter low-power
modes automatically between conversions to save power,
making the devices ideal for portable applications.
The MAX11800/MAX11801 offer two modes of operation:
direct and autonomous. Direct mode allows the application processor to control all touch-screen controller activity. Autonomous mode allows the MAX11800/MAX11801
to control touch-screen activity, thereby freeing the
application processor to perform other functions. In
autonomous mode, the devices periodically scan the
touch screen for touch events without requiring hostprocessor intervention. This can be used to reduce system power consumption. An on-chip FIFO is used during
autonomous mode to store results and increase effective
data throughput and lower system power.
The MAX11800–MAX11803 support data-tagging,
which records the type of measurement performed; X,
Y, Z1, or Z2, and the type of touch event; initial touch,
continuing touch, or touch release.
The MAX11800/MAX11802 support the SPI™ serial bus.
The MAX11801/MAX11803 support the I2C serial bus.
The MAX11800–MAX11803 are available in 12-pin TQFN
and 12-pin WLP packages, and are specified over the
-40°C to +85°C (extended) and -40°C to +105°C (automotive) temperature ranges.
Applications
Mobile Communication
Devices
PDAs, GPS Receivers,
Personal Navigation
Devices, Media Players
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
4-Wire Touch-Screen Interface
X/Y Coordinate and Touch Pressure Measurement
Ratiometric Measurement
12-Bit SAR ADC
Single 1.7V to 3.6V Supply
Two Operating Modes—Direct and Autonomous
Data Tagging Provides Measurement and Touch
Event Information
Data Filtering Provides Noise Reduction
Aperture Mode† Provides Spatial Filtering
Digital Processing Reduces Bus Activity and
Interrupt Generation
Programmable Touch-Detect Pullup Resistors
Auto Power-Down Control for Low-Power
Operation
25MHz SPI Interface (MAX11800/MAX11802)
400kHz I2C Interface (MAX11801/MAX11803)
1.6mm x 2.1mm, 12-Pin WLP and 4mm x 4mm,
12-Pin TQFN
Low-Power Operation
343µW at VDD = 1.7V, 34.4ksps
888µW at VDD = 3.3V, 34.4ksps
ESD Protection
±4kV HBM
±8kV HBM (X+, X-, Y+, Y-)
±1kV CDM
±200V MM
Ordering Information
PART
MAX11800ETC+
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
12 TQFN-EP**
MAX11800GTC/V+
-40°C to +105°C
MAX11800EWC+T*
-40°C to +85°C
12 WLP
-40°C to +85°C
12 TQFN-EP**
MAX11801ETC+
12 TQFN-EP**
POS Terminals
MAX11801GTC/V+
-40°C to +105°C
Handheld Games
MAX11801EWC+T*
-40°C to +85°C
12 WLP
MAX11802ETC+T
-40°C to +85°C
12 TQFN-EP**
MAX11802EWC+T*
-40°C to +85°C
12 WLP
MAX11803ETC+T
-40°C to +85°C
12 TQFN-EP**
MAX11803EWC+T*
-40°C to +85°C
12 WLP
Automotive Center
Consoles
Portable Instruments
Typical Operating Circuits and Pin Configurations appear
at end of data sheet.
SPI is a trademark of Motorola, Inc.
†Patents pending.
Features
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12 TQFN-EP**
*Future product—contact factory for availability.
**EP = Exposed pad.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
/V denotes an automotive qualified part.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1
MAX11800–MAX11803
General Description
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
TABLE OF CONTENTS
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8
I2C Timing Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
SPI Timing Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Functional Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Position Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Pressure Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Touch-Detect Modes and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
PUR and PUF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Idle Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Features Common to the MAX11800–MAX11803 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Averaging Modes and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Data Tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Panel Setup, Measurement, and Scan Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Direct Conversion Mode Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Interrupt Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Panel Setup Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Panel Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Auxiliary Measurement Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Autonomous Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Measurement Operations
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Delayed Touch Detection During Mode Transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
FIFO Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Clearing FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
FIFO Data Block Readback Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
FIFO Data Word Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Block Readback Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Clearing Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Aperture Modes and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Aperture Range Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
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_______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
FIFO Aperture Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Using Aperture Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
Examples of Using Aperture Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
SPI Communication Sequence (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
SPI Configuration Register Write (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
SPI Configuration or Result Register Read (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
SPI Conversion Command (MAX11800/MAX11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
I2C-Supported Sequence (MAX11801/MAX11803) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
I2C Configuration Register Write (MAX11801/MAX11803) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
I2C Configuration or Result Register Read (MAX11801/MAX11803) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
I2C Conversion Command (MAX11801/MAX11803) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Command and Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
User-Accessible Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
Status and Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Data Readback Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Autonomous Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Direct Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Panel Setup and Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
User Configuration Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
General Status Register (0x00) (Read Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
General Configuration Register (0x01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48
Measurement Resolution Configuration Register (0x02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48
Measurement Averaging Configuration Register (0x03) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
ADC Sampling Time Configuration Register (0x04) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
Panel Setup Timing Configuration Register (0x05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Delayed Conversion Configuration Register (0x06) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
Touch-Detect Pullup Timing Configuration Register (0x07) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
Autonomous Mode Timing Configuration Register (0x08) (MAX11800/MAX11801) . . . . . . . . . . . . . . . . . . . . . . . .51
Aperture Configuration Register (0x09) (MAX11800/MAX11801) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
Auxiliary Measurement Configuration Register (0x0A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Operating Mode Configuration Register (0x0B) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
MAX11800/MAX11802 Typical Operating Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
MAX11801/MAX11803 Typical Operating Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
Pin Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
Chip Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
_______________________________________________________________________________________
3
MAX11800–MAX11803
TABLE OF CONTENTS (continued)
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
LIST OF FIGURES
Figure 1. I2C Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Figure 2. SPI Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Figure 3a. MAX11800/MAX11801 Operation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Figure 3b. MAX11802/MAX11803 Operation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Figure 4. Position Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Figure 5. Pressure Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Figure 6. Touch-Detection Circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Figure 7. Touch-Detection Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Figure 8. State Machine Transitions (Direct Conversion Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Figure 9. Continuous Interrupt Mode (Direct Conversion Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Figure 10. Edge Interrupt Mode (Direct Conversion Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Figure 11. Command and Measurement Flow (DCM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Figure 12. Panel Setup and Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Figure 13. Combined Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Figure 14. State Machine Transitions––Autonomous Conversion Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Figure 15. Clear-on-Read Interrupt Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Figure 16. Aperture Usage Example Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Figure 17. SPI Single Configuration Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Figure 18. SPI Multiple Configuration Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Figure 19. SPI Single-Byte Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
Figure 20. SPI Multiple-Byte Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Figure 21. SPI Conversion Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Figure 22. I2C Single Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Figure 23. I2C Multiple Register Write Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
Figure 24. I2C Multiple Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Figure 25. I2C Streamlined Register Read Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
Figure 26. I2C Conversion Command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42
4
_______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Table 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Table 2. Operating Modes, Conditions, and Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Table 3. Summary of Physical Panel Settings for Supported Measurement Types . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Table 4. Median Averaging Operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Table 5. Data Word Structure (All Direct Conversion Modes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Table 6. Measurement and Event Tags (Continuous Interrupt Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Table 7. Measurement and Event Tags (Edge Interrupt Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Table 8. Panel Setup Command Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Table 9. Panel Measurement Command Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Table 10. FIFO Data Block Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Table 11. FIFO Data Word Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Table 12. FIFO Data Measurement Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Table 13. FIFO Event Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Table 14. Readback and FIFO Contents with Aperture Mode Enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Table 15. Readback and FIFO Contents with Aperture Mode Disabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Table 16. SPI Command and Data Format: 8 Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Table 17. I2C Command and Data Format: 8 Bits Plus ACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Table 18. Status and Configuration Registers
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
Table 19. FIFO Data Readback Command (Autonomous Mode Only––MAX11800/MAX11801) . . . . . . . . . . . . . . . .45
Table 20. Data Readback Commands (Direct Mode Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Table 21. I2C Readback Register Settings Following Conversion Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
Table 22. Measurement Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
_______________________________________________________________________________________
5
MAX11800–MAX11803
LIST OF TABLES
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Table 1. Terminology
TERM
Panel,
Touch Screen,
Touch Panel
TSC
Resistive Touch Sensor: Panel, or touch screen, or touch panel are used interchangeably to denote the
resistive touch sensor.
Touch-Screen Controller: Devices attached to a touch screen that provide the interface between an
application processor (AP) and touch screen.
X+
X Position Positive I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and
measurement details.
X-
X Position Negative I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and
measurement details.
Y+
Y Position Positive I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and measurement
details.
Y-
Y Position Negative I/O: Analog I/O from resistive touch screen. See Figure 4 for configuration and
measurement details.
RTOUCH
Touch Resistance: Represents the resistance between the X and Y planes of a resistive touch screen during a
touch event.
Z1
Z1 Measurement: A resistive touch-screen measurement to determine the resistance between the two planes
within the panel sensor during a touch event (RTOUCH). See Figure 5 for configuration and measurement details.
Z2
Z2 Measurement: A resistive touch-screen measurement to determine the resistance between the two planes
within the panel sensor during a touch event (RTOUCH). See Figure 5 for configuration and measurement details.
AUX
ADC
Auxiliary Input: Analog input to the MAX11800–MAX11803 that can be used to monitor external conditions
such as battery voltage or temperature.
Analog-to-Digital Converter: Circuit used to transform analog information into a form suitable for digital operations.
AP
Application Processor: An external microcontroller or microprocessor that interfaces to and controls the
general operation of the MAX11800–MAX11803.
AVG
Averaging Mode: The ability to average consecutive measurement results to reduce noise from switch
bounce, power-supply ripple, and incomplete settling.
MAF
Median Averaging Filter: The MAF first removes the minimum and maximum samples before taking the
average of the remaining sample set.
SAF
Straight Averaging Filter: The SAF takes the average of an entire sample set.
TDM
Touch-Detect Mode: An untimed mode that monitors the panel for a touch using a user-selectable panel
pullup resistor of either 50k or 100k.
DCM
ACM
6
DEFINITION
Direct Conversion Mode: A mode of operation in which the AP requests individual panel setup and
conversion operations or automated combinations of measurements (X and Y, X and Y and Z1, or X and Y and
Z1 and Z2). The AP maintains control over the initiation of panel setup, measurements, and the sampling
f
Autonomous Conversion Mode: A mode of operation in which the MAX11800/MAX11801 idle in TDM until a
touch event occurs. After a touch is detected, the MAX11800/MAX11801 begin an automated sequence of
measurements determined by the user configuration registers.
PSU
Panel Setup Command: User-programmable modes for the purpose of allowing the panel sufficient time to
settle, prior to the start of measurements. PSU commands configure the on-chip multiplexer in preparation to
perform either X, Y, Z1, or Z2 measurements. Durations can either be specified and managed by the
MAX11800–MAX11803 (in ACM and DCM) or managed by the AP (in DCM).
PMC
Panel Measurement Command: Individual measurements of X or Y position and Z1 or Z2 pressure measurements.
CMC
Combined Measurement Command: Combinations of PMCs (X and Y, X and Y and Z1, or X and Y and Z1 and
Z2) offered by the MAX11800–MAX11803 and executed in series to reduce AP bus and interrupt activity.
_______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
MAX11800–MAX11803
Table 1. Terminology (continued)
TERM
DEFINITION
FIFO
First-In First-Out Memory: The MAX11800–MAX11803 contain a 1024-bit FIFO that is used to store conversion
results when operating in autonomous conversion mode. FIFO depth indicates the number of words (16-bit
quantity) in the FIFO.
Scan
Scan: Generally, a single sequence of operations performed in DCM or ACM. The operations could include a
panel setup operation, followed by a panel measurement operation, or a combined measurement operation.
Scan Block
Scan Block: Generally, a sequence of multiple operations performed in DCM or ACM. The operations could
include panel-setup operations, panel-measurement operations, or combined measurement operations.
Timed Scan
Timed Scan: A scan or scan block operation that uses the on-chip oscillator and timer. The timer is controlled
through the configuration registers and represents an array of fixed (time) quantities that are user selectable
(MAX11800/MAX11801).
Untimed Scan Untimed Scan: A scan or scan block operation that is controlled by the AP. This only applies to DCM.
TAG
ETAG
Data Tag: Information appended to the end of an ADC conversion result. Tags indicate the type of measurement and
touch status associated with each panel observation. See the definitions for ETAG and MTAG (also in Table 1).
Event Tag: Data tags indicating the panel touch status observed during a measurement.
MTAG
Measurement Tag: Data tag indicating the type of measurement read back by the AP (either X, Y, Z1, or Z2).
TIRQ
Touch Interrupt Request: Active-low interrupt, indicating that a touch is present (CINT) or has been initiated
(EINT) in DCM, or that new data is available in the FIFO in ACM.
EINT
Edge Interrupt Mode: Indicates, through TIRQ, that a touch has been initiated (EINT) in DCM. The duration that
TIRQ is low is user programmable.
CINT
Continuous Interrupt Mode: Indicates, through TIRQ, that a touch is present (CINT) in DCM. TIRQ goes low to
indicate the presence of a touch and stays low until the touch event ceases.
CORINT
Clear-on-Read Interrupt Mode: Used in ACM only. TIRQ goes low to indicate the presence of new FIFO data. The
interrupt is cleared when the data is read by the AP (MAX11800/MAX11801).
APER
Aperture Mode: Available in ACM only. Reduces data writes to the FIFO by spatially filtering measurement data.
CONT
Continuous Bit: An option in DCM to return the MAX11800–MAX11803 to a panel setup (wait) mode (PSU) after a
conversion, rather than a return to TDM (recommended only for applications with very long panel settling times and
request controlling their own averaging). The continuous bit resides in bit 0 (R0) of the PSU and PMC registers.
LPM
Low-Power Mode: An idle mode used in DCM/EINT or ACM modes, when a touch is detected at the conclusion of
the last measurement. This indicates a new measurement needs to be requested or scheduled (the touch-detect
pullup is not engaged to save power).
PUR
Pullup Rough: A fast pullup mode, which uses the main X+ switch in parallel with the on-chip resistive pullup
(50kΩ/100kΩ) to quickly slew the touch panel capacitances. RPUR ≤ 10Ω typical.
PUF
Pullup Fine: A slow (fine) pullup mode, which uses the on-chip resistive pullup to slew the touch-panel
capacitances to their final values (RPUF = 50kΩ or 100kΩ) typical and is required for all applications.
SAR ADC
Successive Approximation Register ADC: An analog-to-digital converter that converts a continuous analog
waveform into a discrete digital representation through a binary search through all possible quantization levels
before finally converging upon a digital output for each conversion.
I2C
Inter-Integrated Circuit: A multimaster serial computer bus that is used to attach low-speed peripherals to other
components using two bidirectional open-drain lines, serial data (SDA) and serial clock (SCL), pulled up with
resistors.
SPI
Serial Peripheral Interface: A serial interface in which a master device supplies clock pulses to exchange data
serially with a slave over two data wires (master-slave and slave-master).
_______________________________________________________________________________________
7
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
ABSOLUTE MAXIMUM RATINGS
VDD to GND ...........................................................-0.3V to +4.0V
X+, X-, Y+, Y-, AUX, TIRQ to GND ........................-0.3V to +4.0V
SCL, CLK, SDA, DIN, A0, CS, A1, DOUT to GND.-0.3V to +4.0V
Maximum Current into Any Pin .........................................±50mA
Continuous Power Dissipation (TA = +70°C)
12-Pin TQFN (derate 24.4mW/°C above +70°C) ....1951.2mW
12-Pin WLP (derate 6.5mW/°C above +70°C) ..........518.8mW
Operating Temperature Ranges
MAX1180_E_ _..................................................-40°C to +85°C
MAX1180_G_ _ ...............................................-40°C to +105°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature ......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11800E–MAX11803E), TA = -40°C to +105°C (MAX11800G/MAX11801G), unless otherwise noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
10
11
Bits
ADC
ADC Resolution
No missing codes
Differential Nonlinearity
DNL
12-bit resolution
±1.5
LSB
Integral Nonlinearity
INL
12-bit resolution
±1.5
LSB
±2
LSB
Offset Error
Gain Error
±4
Throughput
LSB
105
ksps
TOUCH SENSORS (X+, X-, Y+, Y-, AUX)
Switch On-Resistance
VDD = 1.7V
7
12
VDD = 3.3V
5
10
Switch Driver Current
Input Voltage Range
Ω
50
mA
0
VDD
V
1.7
3.6
V
POWER SUPPLY (VDD)
Supply Voltage
VDD
Power-down mode. All digital
inputs static.
TDM. All digital inputs static.
Does not include panel currents
when touched.
Supply Current
1
3.6V
2
3.6V
7
Timed LPM. All digital inputs
static. Does not include panel
currents when touched.
1.7V
9
20
3.3V
16
40
AUX conversions at 34.4ksps
equivalent rate, SPI
1.7V
216
400
3.3V
273
550
AUX conversions at 34.4ksps
equivalent rate, I2C
1.7V
202
400
3.3V
269
550
AUX conversions at 34.4ksps
equivalent rate, SPI
1.7V
367
3.3V
901
AUX conversions at 34.4ksps
equivalent rate, I2C
1.7V
343
3.3V
888
Power Consumption
8
1.7V
_______________________________________________________________________________________
μA
μW
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
(VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11800E–MAX11803E), TA = -40°C to +105°C (MAX11800G/MAX11801G), unless otherwise noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL INPUTS (SDA, DIN, SCL, CLK, A0, CS, A1)
Input Logic-High Voltage
VIH
Input Logic-Low Voltage
VIL
Input Leakage Current
IIN
Input Hysteresis
0.7 x
VDD
VIN = 0V or VDD
V
-1
VHYS
Input Capacitance
0.3 x
VDD
V
+1
μA
0.5 x
VDD
V
6
pF
DIGITAL OUTPUTS (SDA, DOUT, TIRQ)
Output Logic-High
DOUT, ISOURCE = 1mA
0.9 x
VDD
TIRQ, CMOS configuration, ISOURCE = 1mA
0.9 x
VDD
VOH
V
Output Logic-Low—TIRQ, DOUT
VOL
ISINK = 1mA
0.4
Output Logic-Low—SDA
VOL
ISINK = 3mA
0.4
TIRQ Pullup Resistor
125
V
V
kΩ
I2C TIMING CHARACTERISTICS
(VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11801E and MAX11803E), TA = -40°C to +105°C (MAX11801G), unless otherwise
noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted. See Figure 1.)
PARAMETER
Serial-Clock Frequency
Bus Free Time
SYMBOL
fSCL
tBUF
Hold Time for START Condition
CONDITIONS
tHD;STA
MIN
0
TYP
MAX
UNITS
400
kHz
Bus free time between STOP and START
condition
1.3
μs
After this period, the first clock pulse is
generated
0.6
μs
SCL Pulse-Width Low
tLOW
1.3
μs
SCL Pulse-Width High
tHIGH
0.6
μs
Setup Time for Repeated START
(Sr) Condition
tSU;STA
0.6
μs
Data Hold Time
tHD;DAT
0
Data Setup Time
tSU;DAT
100
tR, tF
Receiving
20 +
CB/10
300
ns
Transmitting
20 +
CB/10
250
ns
SDA and SCL Rise/Fall Time
SDA and SCL Fall Time
Setup Time for STOP Condition
tTF
tSU;STO
Bus Capacitance Allowed
CB
Pulse Width of Suppressed Spike
tSP
900
ns
ns
0.6
μs
VDD = 1.7V to 2.7V
10
100
VDD = 2.7V to 3.6V
10
400
50
pF
ns
_______________________________________________________________________________________
9
MAX11800–MAX11803
ELECTRICAL CHARACTERISTICS (continued)
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
SPI TIMING CHARACTERISTICS
(VDD = 1.7V to 3.6V, TA = -40°C to +85°C (MAX11800E and MAX11802E), TA = -40°C to +105°C (MAX11800G), unless otherwise
noted. Typical values are at TA = +25°C and VDD = 3.3V, unless otherwise noted. See Figure 2.)
PARAMETER
SYMBOL
CLK Frequency
CONDITIONS
MIN
TYP
fCLK
MAX
UNITS
25
MHz
CLK Period
tCP
40
ns
CLK Pulse-Width High
tCH
18
ns
CLK Pulse-Width Low
tCL
18
ns
CS Low to 1st CLK Rise Setup
tCSS0
18
ns
0
ns
18
ns
CS Low After 0th CLK Rise Hold
tCSH0
To prevent a 0th CLK read from being taken
as a 1st read in a free-running application
CS High to 17th CLK Setup
tCSS1
To prevent a 17th CLK read from being
recognized by the device in a free-running
application
CS High After 16th CLK Falling
Edge Hold
tCSH1
0
ns
CS Pulse-Width High
tCSW
18
ns
DIN to CLK Setup
tDS
25
ns
DIN Hold After CLK
tDH
0
ns
DOUT Transition Valid After CLK
Rise
tDOT
Output transition time
DOUT Remains Valid After CLK
Rise
tDOH
Output hold time
3
DOUT Valid Before CLK Rise
tDO1
tDO1 = tCP - tDOT
10
CS Rise to DOUT Disable
tDOD
CLOAD = 20pF
CLK Rise to DOUT Enable
tDOE
CLOAD = 20pF. Minimum = hold time with
regard to 8th CLK read. Maximum =
transition time with regard to 8th CLK read.
25
ns
ns
3
tF
SDA
tBUF
tSU;DAT
tR
tLOW
SCL
tHD;STA
tSP
tHIGH
tHD;STA
S
tHD;DAT
tF
tSU;STO
tSU;STA
Sr
P
Figure 1. I2C Timing Diagram
10
ns
______________________________________________________________________________________
S
40
ns
25
ns
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
tCP
MAX11800–MAX11803
tDS
tCSH0
tSCH1
tDH
tCSS0
tCSW
tCH
CS
tCL
tCSS1
CLK
DIN
DOUT
1
0
X
A6
A5
A4
A3
A2
A1
A0
8
9
W
D7
16
D6
D5
D3
D4
D1
D2
D0
HIGH-Z
SPI WRITE OPERATION
tDS
tCP
tCSS0
DOUT
tDO1
tCL
CLK
1
X
A6
HIGH-Z
A5
A4
A3
A2
tDO0
tDOE
tCH
CS
DIN
tDOH
tDH
A1
A0
8
9
R
X
D7
16
X
X
X
X
X
X
X
D6
D5
D4
D3
D2
D1
D0
HIGH-Z
SPI READ OPERATION
Figure 2. SPI Timing Diagram
______________________________________________________________________________________
11
Typical Operating Characteristics
(VDD = 1.8V at TA = -40°C to +85°C (TA = -40°C, TA = 0°C, TA = +25°C, and TA = +85°C), 12-bit mode, all measurements using
noncontinuous AUX input. SPI = 10MHz and I2C = 400kHz, unless otherwise noted. Resistive touch-screen panel (X+ to X- = 608Ω,
Y+ to Y- = 371Ω).)
50
40
30
DATA TAKEN WITH
RESISTIVE TOUCH
SENSOR
cps = COORDINATES PER SECOND
0
20 40 60 80 100 120 140 160 180 200
0
20 40 60 80 100 120 140 160 180 200
0
0
MAX11800 toc03
20 40 60 80 100 120 140 160 180 200
SAMPLING RATE (cps)
SAMPLING RATE (cps)
SUPPLY CURRENT IN POWER-DOWN
vs. TEMPERATURE
SWITCH RESISTANCE
vs. SUPPLY VOLTAGE
SWITCH RESISTANCE
vs. TEMPERATURE
8
MAX11800 toc04
0.36
0.32
7
0.28
RON (I)
0.24
0.20
5
0.16
7
X+
Y-
4
-15
10
35
60
3
85
1.6
2.0
2.4
2.8
3.2
1
3.6
-40
-15
VDD (V)
10
35
60
TEMPERATURE (NC)
CHANGE IN ADC OFFSET
vs. TEMPERATURE
2
1
0
-1
-2
-3
MAX11800 toc08
3
4
3
DELTA FROM +25NC (LSB)
MAX11800 toc07
4
DELTA FROM +25NC (LSB)
X-
2
CHANGE IN ADC GAIN
vs. TEMPERATURE
-4
Y-
4
3
X-
0.04
-40
X+
5
0.12
0.08
Y+
6
Y+
6
TEMPERATURE (NC)
2
1
0
-1
-2
-3
-40
-10
20
50
TEMPERATURE (NC)
12
cps = COORDINATES PER SECOND
SAMPLING RATE (cps)
0.40
0
2
MAX11800 toc06
0
3
1
1
cps = COORDINATES
PER SECOND
RON (I)
10
2
MAX11800 toc05
20
3
DIRECT EDGE
INTERRUPT MODE
4
SUPPLY CURRENT (FA)
SUPPLY CURRENT (FA)
SUPPLY CURRENT (FA)
60
DIRECT CONTINUOUS
INTERRUPT MODE
4
5
MAX11800 toc02
AUTONOMOUS MODE
70
0
5
MAX11800 toc01
90
80
AVERAGE SUPPLY CURRENT
vs. SAMPLING RATE
AVERAGE SUPPLY CURRENT
vs. SAMPLING RATE
AVERAGE SUPPLY CURRENT
vs. SAMPLING RATE
POWER-DOWN SUPPLY CURRENT (µA)
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
80
110
-4
-40
-10
20
50
TEMPERATURE (NC)
______________________________________________________________________________________
80
110
85
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
80
60
40
20
sps = SAMPLES PER SECOND
20 40 60 80 100 120 140 160 180 200
8
16
32
24
2.06
2.04
2.02
2.00
1.98
1.96
1.94
2.00
1.98
VDD = 3.6V
1.96
1.94
1.92
1.90
-40
-15
3.0
VDD (V)
10
35
160
DATA TAKEN WITH
RESISTIVE TOUCH SENSOR
140
AUTONOMOUS MODE
120
60
85
100
DIRECT CONTINUOUS MODE
80
60
cps = COORDINATES
PER SECOND
40
20
1.92
2.4
MAX11800 toc11
VDD = 1.8V
2.02
POWER CONSUMPTION
vs. SAMPLE RATE
POWER CONSUMPTION (FW)
2.08
1.8
VDD = 3.0V
2.04
TEMPERATURE (NC)
INTERNAL OSCILLATOR CLOCK
FREQUENCY vs. SUPPLY VOLTAGE
1.90
2.06
EQUIVALENT SAMPLING RATE (ksps)
SAMPLING RATE (sps)
MAX11800 toc12
0
ksps = KILO-SAMPLES PER SECOND
0
2.08
3.6
MAX11800 toc13
0.5
0
INTERNAL OSCILLATOR CLOCK FREQUENCY (MHz)
1.0
AUXILIARY INPUT DATA
SAMPLED AT 1ksps AND
2ksps WITH EIGHT AND
16 SAMPLES
AVERAGING
ENABLED
100
SUPPLY CURRENT (FA)
1.5
INTERNAL OSCILLATOR CLOCK FREQUENCY (MHz)
SUPPLY CURRENT (FA)
2.0
MAX11800 toc10
DIRECT CONVERSION
MODE—AUXILIARY INPUT
2.5
120
MAX11800 toc09
3.0
0
DIRECT EDGE MODE
0
50
100
150
200
SAMPLE RATE (cps)
______________________________________________________________________________________
13
MAX11800–MAX11803
Typical Operating Characteristics (continued)
(VDD = 1.8V at TA = -40°C to +85°C (TA = -40°C, TA = 0°C, TA = +25°C, and TA = +85°C), 12-bit mode, all measurements using
noncontinuous AUX input. SPI = 10MHz and I2C = 400kHz, unless otherwise noted. Resistive touch-screen panel (X+ to X- = 608Ω,
Y+ to Y- = 371Ω).)
AVERAGE SUPPLY CURRENT
INTERNAL OSCILLATOR CLOCK
AVERAGE SUPPLY CURRENT
vs. SAMPLING RATE
FREQUENCY vs. TEMPERATURE
vs. SAMPLING RATE
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Pin Description
PIN
MAX11800/MAX11802
TQFN
14
WLP
MAX11801/MAX11803
TQFN
NAME
FUNCTION
WLP
1
C1
1
C1
X+
X+ Channel Input/Output
2
B1
2
B1
VDD
Power Supply. Bypass VDD to GND with a 1μF capacitor.
3
B2
3
B2
GND
Ground
4
A1
4
A1
X-
X- Channel Input/Output
5
A2
5
A2
Y-
Y- Channel Input/Output
6
A3
6
A3
TIRQ
Active-Low Touch Interrupt Output
7
A4
—
—-
DIN
SPI Serial Data Input
8
B4
—
—
CLK
SPI Serial Data Clock Input
9
C4
—
—
CS
10
B3
—
—
DOUT
SPI Data Output
11
C3
11
C3
AUX
Auxiliary Input
12
C2
12
C2
Y+
—
—
7
A4
SDA
I2C Serial Data Bus Input/Output
—
—
8
B4
SCL
I2C Serial Data Clock Input
—
—
9
C4
A0
I2C Address Input Bit 0
—
—
10
B3
A1
I2C Address Input Bit 1
EP
—
EP
—
EP
Exposed Pad. Connected to ground.
SPI Chip-Select Input
Y+ Channel Input/Output
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
POWER
AND
BIAS
MAX11800/MAX11801
VDD
AUX
DOUT (A1)
X+
MUX
XY+
Y-
SERIAL INTERFACE
PHYSICAL LAYER
(ANALOG INTERFACE)
SAR
ADC
TOUCHSCREEN
INTERFACE
LOGIC
CORE
SIF
PHY
CS (A0)
CLK (SCL)
DIN (SDA)
AUTONOMOUS
MODE ENGINE
V
DD
INTERNAL
CLOCK
INTERRUPT
GENERATION
ENGINE
FIFO
TIRQ
GND
POWER
AND
BIAS
MAX11802/MAX11803
VDD
AUX
DOUT (A1)
X+
MUX
XY+
Y-
SERIAL INTERFACE
PHYSICAL LAYER
(ANALOG INTERFACE)
SAR
ADC
TOUCHSCREEN
INTERFACE
LOGIC
CORE
V
DD
SIF
PHY
CS (A0)
CLK (SCL)
DIN (SDA)
INTERNAL
CLOCK
INTERRUPT
GENERATION
ENGINE
TIRQ
GND
______________________________________________________________________________________
15
MAX11800–MAX11803
Functional Diagrams
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Detailed Description
The MAX11800–MAX11803 contain standard features
found in a typical resistive touch-screen controller as
well as advanced features. Standard features included
in the MAX11800–MAX11803 are:
• 4-wire touch-screen interface
• X/Y coordinate measurement
• Touch pressure measurement
• Direct conversion operation—requires direct AP
involvement
• Single commands—AP initiates all activity one command at a time
• Ratiometric measurement
• 12-bit SAR ADC
• Single 1.8V to 3.3V supply
• Programmable touch-detect pullup—50kΩ or
100kΩ
• Auto power-down control for low-power operation
• 400kHz I2C interface (MAX11801/MAX11803)
Advanced features found in the MAX11800–MAX11803
include:
• Autonomous conversion operation—minimal AP
involvement (MAX11800/MAX11801)
• On-chip FIFO—buffers up to 16 consecutive measurements (MAX11800/MAX11801)
• Data tagging—records measurement and touchevent information
• Filtering—reduces noise using straight or median
averaging
• Aperture mode—provides spatial filtering
(MAX11800/MAX11801)
• Combined commands—multiple operations performed with a single AP command
• Digital processing to reduce serial bus activity
• Digital processing to reduce interrupt generation
16
• User-programmable acquisition modes
• Programmable interrupt output drive
• 25MHz SPI interface (MAX11800/MAX11802)
The MAX11800–MAX11803 operate in one of two toplevel modes: direct conversion mode (DCM) or
autonomous conversion mode (ACM). Direct conversion
mode requires the AP to initiate all activity to and from
the MAX11800–MAX11803. DCM is the operating mode
that most standard resistive touch-screen controllers
use. ACM allows the MAX11800/MAX11801 to perform
measurements automatically and inform the AP when
they are complete, reducing data transfers on the serial
bus as well as generating fewer interrupt requests. The
MAX11800/MAX11801 can operate in the standard
mode that is familiar to users, or in the advanced features mode to provide additional flexibility.
Both DCM and ACM support averaging, data tagging,
and combined commands. Certain commands and
operations are only available in DCM, while others are
only available in ACM. See Figures 3a and 3b and
Table 2 for details.
Position Measurements
Position measurements determine either the X or Y
coordinates of the point of contact on the panel sensor.
Allow adequate time for the panel to settle when switching between X and Y measurements. Figure 4 shows
the physical setup of the panel when performing position measurements.
The element RTOUCH represents the resistance between
the X and Y planes of the panel sensor. RTOUCH does
not contribute to the error when performing position measurements. R TOUCH affects the panel settling time
required between each valid measurement.
The panel end-to-end resistance in the direction of
measurement determines the power applied across the
panel. The panel dissipates power in the X elements
when performing an X direction measurement and dissipates power in the Y elements when performing a Y
direction measurement.
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
MAX11800–MAX11803
MAX11800
MAX11801
SETUP
REGISTERS
SETUP
REGISTERS
OPERATION MODES
REGISTER 0x0B
DIRECT CONVERSION
(DCM)
REGISTER 0x05
REGISTER 0x6x
REGISTER 0x7x
AUTONOMOUS CONVERSION
(ACM)
REGISTER 0x0B
PANEL SETUP COMMANDS
(PSU)
PANEL SETUP COMMANDS
(PSU)
REGISTER 0x05
REGISTER 0x6x*
PANEL MEASUREMENT
COMMANDS (PMC)
PANEL MEASUREMENT
COMMANDS (PMC)
REGISTER 0x7x*
PANEL COMBINED COMMANDS
(CMC)
REGISTER 0x7x*
REGISTER 0x7x
PANEL COMBINED COMMANDS
(CMC)
REGISTER 0x0A
AUX MEASUREMENT
COMMANDS (AMC)
REGISTER 0x0B
X, Y, Z1, Z2
MEASUREMENTS
REGISTER 0x03
REGISTER 0x0B
AVERAGING MEASUREMENTS
REGISTER 0x01
EDGE INTERRUPT MODE
(EINT)
REGISTER 0x01
CONTINUOUS INTERRUPT MODE
(CINT)
OPERATION
MODE
COMMANDS
N/A
MEASUREMENT
TYPES
MEASUREMENT TAG (MTAG)
(IF CONT = 1, NO FIFO)
REGISTER 0x0B
AVERAGING MEASUREMENTS
REGISTER 0x03
REGISTER 0x0B
N/A
INTERRUPT
TYPES
N/A
CLEAR-ON-READ INTERRUPT
(CORINT)
N/A
EVENT TAG (ETAG)
(IF CONT = 1, NO FIFO)
X, Y, Z1, Z2
MEASUREMENTS
DATA TAGGING
TYPES
EVENT TAG (ETAG)
(USES FIFO)
MEASUREMENT TAG (MTAG)
(USES FIFO)
N/A
APERTURE
APERTURE SETTINGS
REGISTER 0x09
REGISTER 0x01
TIRQ CONFIGURATION
TIRQ
TIRQ CONFIGURATION
REGISTER 0x01
REGISTER 0x02
REGISTER 0x04
REGISTER 0x06
ADC RESOLUTION
AND TIMING
ADC
ADC RESOLUTION
AND TIMING
REGISTER 0x02
REGISTER 0x04
REGISTER 0x06
REGISTER 0x07
PUR AND PUF TIMING
TDM TIMING
PUR AND PUF TIMING
REGISTER 0x07
N/A
AUTO TIMING
TINIT AND SCANP TIMING
REGISTER 0x08
*THESE REGISTERS CANNOT BE ALTERED WHEN AUTONOMOUS MODE IS ACTIVE. THEY SHOULD BE INITIALIZED BEFORE AUTONOMOUS MODE IS ACTIVATED.
Figure 3a. MAX11800/MAX11801 Operation Modes
______________________________________________________________________________________
17
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
MAX11802
MAX11803
OPERATION MODES
SETUP
REGISTERS
REGISTER 0x05
REGISTER 0x6x
PANEL SETUP COMMANDS
(PSU)
REGISTER 0x7x
PANEL MEASUREMENT
COMMANDS (PMC)
REGISTER 0x7x
PANEL COMBINED COMMANDS
(CMC)
REGISTER 0x0A
AUX MEASUREMENT
COMMANDS (AMC)
REGISTER 0x0B
X, Y, Z1, Z2
MEASUREMENTS
REGISTER 0x03
REGISTER 0x0B
AVERAGING MEASUREMENTS
REGISTER 0x01
EDGE INTERRUPT MODE
(EINT)
REGISTER 0x01
CONTINUOUS INTERRUPT MODE
(CINT)
COMMANDS
MEASUREMENT
TYPES
INTERRUPT
TYPES
EVENT TAG (ETAG)
MEASUREMENT TAG (MTAG)
DATA TAGGING
TYPES
REGISTER 0x01
TIRQ CONFIGURATION
TIRQ
REGISTER 0x02
REGISTER 0x04
REGISTER 0x06
ADC RESOLUTION
AND TIMING
ADC
REGISTER 0x07
PUR AND PUF TIMING
TDM TIMING
Figure 3b. MAX11802/MAX11803 Operation Modes
18
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
OPERATION
PSU PMC CMC TDM LPM AVG
MODE
FIFO APER
COR
X, Y,
PUR
EINT CINT
CONT MTAG ETAG
INT
Z1, Z2
PUF
DCM
MAX11800–
MAX11803
Yes
Yes
Yes
Yes
No
Yes
No
No
Yes
Yes
Yes 2
Yes 2
Yes
Yes
Yes
No
ACM
MAX11800/
MAX11801
Yes 1
Yes 1 Yes 1
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
No
No
Yes
AUX
No
Yes 3
No
—
Yes 3
No
No
No
No
No
No
No
No
No
No
No
1In ACM, the choices are limited to X and Y scan, or X and Y and Z1 scan, or X and Y and Z1 and Z2 scan.
2In DCM, each ADC conversion is tagged with MTAG and ETAG only when the continuous bit is set (CONT = 1). DCM does not use
the FIFO and, therefore, the AP should request the data at the end of the conversion cycle.
3A separate configuration register for delay time, sampling time, averaging, and ADC resolution settings configures the AUX input.
Pressure Measurements
Z1 and Z2 measurements determine the resistance
between the two planes within the panel sensor during
a touch (RTOUCH). Depending on the known physical
properties of the panel, one of two equations extract the
value of RTOUCH, providing information about the pressure and area of the touch applied to the panel. Allow
adequate time for the panel to settle when switching
between position and pressure measurements. Figure 5
shows the physical setup of the panel when performing
pressure measurements.
Z1 and Z2 measurements allow observation of the voltage on either side of the effective RTOUCH resistance.
With both Z1 and Z2 measurements available, compute
RTOUCH as follows:
Y+
PANEL
ADC
INPUT
Y+
PANEL
RTOUCH
⎛X
⎞ ⎛Z
⎞
RTOUCH = RXPLATE ⎜ POSITION ⎟ ⎜ 2 − 1⎟
⎝ 2NBITX ⎠ ⎝ Z1
⎠
If only a Z1 measurement is available, compute
RTOUCH as follows:
X
⎛R
⎞
RTOUCH = ⎜ XPLATE POSITION ⎟
⎝
⎠
2NBITX
The power applied across the panel during pressure
measurements is greatly dependent on RTOUCH and
the physical position of the touch. The maximum power
dissipation in the panel during a pressure measurement
is approximately PZ = VDD2/RTOUCH. This maximum
power dissipation condition is observed when the point
of contact is in the top left corner of the panel sensor.
VDD
X+
Y-
Y+
PANEL
RTOUCH
X-
Y
⎛
⎞
⎛ 2NBITZ ⎞
− 1⎟ − RYPLATE ⎜ 1 − POSITION ⎟
⎜⎝
⎝
⎠
Z1
2NBITY ⎠
VDD
RTOUCH
X-
X+
ADC
INPUT
VDD
RTOUCH
YX-
Y+
PANEL
X+
Y-
X-
X+
Y-
ADC
INPUT
ADC
INPUT
VDD
X POSITION MEASUREMENT
Figure 4. Position Measurements
Y POSITION MEASUREMENT
Z1 PRESSURE MEASUREMENT
Z2 PRESSURE MEASUREMENT
Figure 5. Pressure Measurements
______________________________________________________________________________________
19
MAX11800–MAX11803
Table 2. Operating Modes, Conditions, and Options
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
a touch is detected. The YMSW and TSW transistors
are on, and the XPSW and PSW transistors are off. With
no touch present, the Y- input of the TSC is at ground
and the X+ input is at VDD - V TN, where VTN is the
threshold voltage of the TSW nMOS device. This is a
low-power mode in which no current is consumed until
a panel touch occurs. When a touch is present on the
panel, the touch-screen controller (TSC) X+ input is
pulled low by the touch panel plate resistance and the
YMSW transistor. This causes TOUCH to assume a
logic high and the MAX11800–MAX11803 either issue
the TIRQ interrupt for direct conversion modes or begin
self-timed scans for autonomous conversion mode.
The value of the user-defined R TD depends on the
characteristics of the panel. To ensure reliable detection values, worst-case panel resistance must be
checked against RTD. The interaction between RTD and
the panel (or external noise rejecting) capacitance
determines how quickly the panel can be switched from
measurement modes back to touch monitoring mode
without reporting false touches or erroneous tags due
to panel settling.
Panel touch status is also required to tag data from a
completed scan and measurement operation. Following
each scan operation, the panel must be returned to
TDM to determine if the panel is still being touched and
if the data obtained during the scan operation should
be considered valid. This operation is required since
the panel cannot be monitored for the presence of a
touch during the scan and measurement procedure.
The planar end-to-end resistance included in the current path is minimal at this location. Keep the averaging
and panel settling durations to the minimum required
by the application when pressure measurements are
required. Table 3 summarizes the physical panel settings for supported measurement types.
Touch-Detect Modes and Options
Figure 6 shows the internal circuitry in the
MAX11800–MAX11803 used to detect the presence of
a touch on the panel. The selection of the pullup resistance value (RTD = touch-detect resistance) and the
durations of the rough pullup interval (PUR = lowimpedance pullup) and fine pullup interval (PUF = highimpedance pullup) are user-defined.
The MAX11800–MAX11803 revert to the low-power
panel setup when placed in touch-detect mode (TDM).
Figure 6 shows the active panel drive switches (YMSW
and XPSW are omitted for simplicity). TSW is a dedicated pullup switch used in TDM. TSW is also used during
PUF and TDM. XPSW is activated during PUR periods.
TDRSEL allows the selection of an internal pullup resistor value of either 50kΩ or 100kΩ.
The X and Y touch-screen plates create an open circuit
with no current flow in the panel when the panel is not
being touched. In this case, TOUCH (see Figure 6) is
low. When a touch causes contact between the panel X
and Y plates, a current path is created and TOUCH is
pulled high, as long as RPX + RPY (the sum of panel
end-to-end resistance) is much lower than RTD. Typical
open-circuit panel plate resistances range from 200Ω
to 1000Ω.
The MAX11800–MAX11803 enter high-impedance
pullup mode (50kΩ or 100kΩ) when the panel is not
being touched and the device is idle in this mode until
The MAX11800–MAX11803 must return to TDM after
completing a measurement and making a decision on
the touch status of the panel. The measurement procedure is only completed upon resolution of the touch status and when data is tagged and available for
Table 3. Summary of Physical Panel Settings for Supported Measurement Types
MODE
X+
X-
Y+
Y-
REF+
REF-
X
Y
Z1
Z2
PUR
VDD
ADC_IN
ADC_IN
U
VDD (10Ω)
VDD through
50kΩ or 100kΩ
U
GND
U
GND
GND
U
ADC_IN
VDD
VDD
VDD
U
U
GND
U
ADC_IN
GND
X+
Y+
Y+
Y+
U
XYXX—
U
U
GND
U
—
U
U
U
U
—
TDM or PUF
LPM
Note: The ADC input is fully differential with the negative input internally connected to GND. The MAX11800–MAX11803 control
access to the PUR, PUF, TDM, and LPM, which do not require setup procedures.
U indicates unconnected node.
20
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
PUR and PUF
PUR is a fast pullup mode, which uses the main X+
switch in parallel with the resistive pullup to quickly slew
the panel capacitance. PUF uses only the touch-detect
pullup resistor, RTD. PUR and PUF serve the same function as TDM, but are timed so that the panel can settle
after completing measurements and before rendering
any decisions on the touch status of the panel.
Use the optional PUR mode to reduce the time to tag
data by momentarily placing the panel in a low-impedance (< 10Ω) pullup mode instead of using the available 50kΩ/100kΩ touch-detection pullup resistors. This
operation forces the monitored TSC input high during
the PUR interval. Once the PUR interval expires, a PUF
interval must be allowed so that the panel can recover
and pull the TSC input low in case a touch is present.
The purpose of the PUR mode is to reduce the time
required to determine touch status by avoiding long
pullup time constants caused by high-capacitance
touch panels and the high-impedance on-chip pullup
resistors (RTD). When a touch is present during PUR
intervals, the current through the low-impedance pullup
(XPSW) and panel combination is significantly higher
than that observed in the PUF mode. The durations in
the PUR mode must be matched to the panel charac-
VDD
PSW
RTD
TDRSEL
RTD
TOUCH
Y+
XPSW
PUR
TSW
PUR, PUF, TDM
(TO MAX11800/
MAX11801 LOGIC)
X+
X-
YPANEL
YMSW
PUR, PUF, TDM
MAX11800–
MAX11803
Figure 6. Touch-Detection Circuitry
teristics and the desired scan throughput rates to minimize power dissipation.
While use of the PUR mode is optional, the PUF period
is required for all applications. The PUF interval allows
the panel to resettle following scan or optional PUR
intervals. When a touch is not present, the panel capacitance settles toward VDD through the internal pullup
switch and a portion of the panel resistance (with the
optional PUR mode disabled). When a touch is present,
the panel capacitance settles toward ground through a
portion of the panel resistance, ideally significantly
lower than the selected pullup impedance, RTD. Allow
enough recovery time for settling through the panel
when using a PUR mode. Figure 7 illustrates the touchdetection operations.
Idle Modes
Once the PUF period expires, the preceding measurement data is tagged and made available for readback.
The MAX11800–MAX11803 transition to an appropriate
mode depending on the conversion and interrupt mode
selected.
Features Common to the
MAX11800–MAX11803
Averaging Modes and Options
The MAX11800–MAX11803 contain a programmable
averaging filter. When enabled, this feature allows collecting 4, 8, or 16 consecutive samples for each measurement type requested. The number of the samples
for each measurement type is controlled by configuration register 0x03. The AUX depth input is selected in
configuration register 0x0A. Averaging can be
assigned to each measurement type. For example, X
and Y measurements can use an average of 16 samples, while Z measurements can use one or four samples to save power.
The MAX11800–MAX11803 can be configured to perform one of two statistical operations. One option is a
median averaging filter (MAF). The MAF first removes
outliers before taking the average of the remaining
sample set. The second is a straight averaging filter
(SAF), which takes the average of the entire sample set.
Averaging modes are supported in both direct and
autonomous conversion modes. Both filter types and
position/pressure averaging are controlled by configuration register 0x0B. This allows switching between
direct and autonomous modes using a single configuration write through the serial interface (SIF). Table 4
presents the details of the median averaging operations
of the MAX11800–MAX11803.
______________________________________________________________________________________
21
MAX11800–MAX11803
readback. The characteristics of the return to TDM and
the timing of the decision are configurable through the
touch-detect pullup timing configuration register (0x07).
Program the MAX11800–MAX11803 in the context of
the application to maximize power efficiency and
achieve the desired scan throughput.
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
FAST PULLUP TOUCH DETECTION
(NOTE: INCREASED CURRENT IN PUR MODE DURING TOUCH)
DIGITAL WAVEFORM
DATA VALIDITY IS DETERMINED
(DATA IS TAGGED)
SCAN MODE
PUR MODE
(OPTIONAL)
PUF MODE
TOUCH DETECT
MEASUREMENT COMPLETE—
DATA IS KNOWN
POWER ASSISTED PULLUP PERIOD (10Ω)
PANEL IS ALLOWED TO RESETTLE BEFORE
DETERMINING DATA VALIDITY
IS THERE A TOUCH?
YES = LPM.
NO = TDM.
ANALOG WAVEFORM
VDD
TSC INPUT
TOUCH NOT PRESENT: TSC INPUT
REMAINS HIGH
INITIAL INPUT VOLTAGE
DETERMINED BY LAST SCAN
ACTIVITY
TOUCH PRESENT:
TSC INPUT PULLED LOW
FORCED FAST PULLUP USING
10Ω SWITCH
TIME
NORMAL TOUCH DETECTION
(NOTE: NO PUR PERIOD; ALLOW LONG PULLUP TIMES)
DIGITAL WAVEFORM
DATA VALIDITY IS DETERMINED
(DATA IS TAGGED)
SCAN MODE
MEASUREMENT COMPLETE—
DATA IS KNOWN
PUF MODE
PANEL IS ALLOWED TO RESETTLE BEFORE DETERMINING DATA VALIDITY
(THROUGH 50kΩ/100kΩ PULLUP)
TOUCH DETECT
IS THERE A TOUCH?
YES = LPM.
NO = TDM.
ANALOG WAVEFORM
TSC INPUT
VDD
TOUCH NOT PRESENT:
TSC INPUT PULLED HIGH THROUGH 50kΩ/100kΩ PULLUP
INITIAL INPUT VOLTAGE
DETERMINED BY LAST SCAN
ACTIVITY
TOUCH PRESENT:
TSC INPUT PULLED LOW BY PANEL
TIME
Figure 7. Touch-Detection Operations
22
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
retrieve the data from the last requested measurement
before moving on to the next measurement of the type.
Auxiliary measurement data is not tagged because it is
not related to panel operation. Auxiliary measurement
data is stored and read back identically to the other
direct conversion data. The tag locations for auxiliary
measurement data are always set to 0000b, unless the
read occurs when an auxiliary measurement is in
progress. In this situation, the tag locations read 1111b
and the data stream reads back FFFFh.
Data Tagging
In direct conversion modes, all measurement data is
contained in a 16-bit word. X, Y, Z1, and Z2 information
is logged independently. Each word consists of 12 bits
of measurement data plus a 2-bit measurement type
(MTAG) and a 2-bit event tag (ETAG). The measurement tag identifies whether the data represents an X, Y,
Z1, or Z2 result. The event tag indicates the point at
which the data is sampled (initial, midpress, or release)
during the touch event. When trying to read a result
which is pending an update, the entire data stream is
read back as FFFFh and the event tag as 11b, indicating that the corresponding measurement is in progress
and that the data stream is to be ignored. For combined commands, all data locations requested by the
command are marked FFFFh, pending the completion
of the entire command and the proper tagging of the
data. See Table 5.
Low-Power Modes
There are also two low-power modes, LPM and TDM.
During LPM, all circuitry is off, including the on-chip
touch-detect pullup resistors used in the touch-detect
circuitry. In direct conversion modes, a user-request initiates the next operation and all circuitry is off until a
user-command is received. Therefore, the current consumption is primarily due to junction leakage. In
autonomous conversion mode, an on-chip oscillator
and timer are constantly running. Therefore, the device
current consumption is primarily determined by the
oscillator and timer. During TDM, all circuitry is off
except the on-chip pullup resistor. This is an untimed
mode (oscillator and timer are off) for both ACM and
DCM (no digital current). This mode only consumes
current through the on-chip pullup resistor when a
touch is present.
Direct conversion modes do not use the internal FIFO
or support the aperture (see the Aperture Modes and
Options section) function. Each measurement type is
afforded a single location in the memory. The AP must
Table 4. Median Averaging Operations
AVERAGING MODE
NUMBER OF
SAMPLES TAKEN
NUMBER OF HIGH
SAMPLES REMOVED
NUMBER OF LOW
SAMPLES REMOVED
NUMBER OF
REMAINING SAMPLES
AVERAGED
1
4
1
1
2
2
8
2
2
4
3
16
4
4
8
Table 5. Data Word Structure (All Direct Conversion Modes)
INDEX
Byte
15
14
13
12
11
10
9
8
7
6
5
MSB Byte
4
3
2
1
0
LSB Byte
12-Bit Content
Position MSBs
Position LSBs
Measure
Event
8-Bit Content
Position Data
Trailing Zeros
Measure
Event
______________________________________________________________________________________
23
MAX11800–MAX11803
Combined Commands
Combined commands reduce AP interaction with the
MAX11800–MAX11803 by allowing multiple measurements. For example, the MAX11800–MAX11803 can be
instructed to provide X and Y data, or X and Y and Z1
data, or X and Y and Z1 and Z2 data using a single
command.
Panel Setup, Measurement, and Scan Commands
To simplify measurement procedures, the MAX11800–
MAX11803 support three types of commands: panel
setup commands (PSU), panel measurement commands
(PMC), and combined measurement commands (CMC).
In direct conversion mode, the MAX11800–MAX11803
can use all three types of commands. Using individual
panel setup and measurement commands allow for a
high degree of customization based on decisions made
by the AP, while using combined commands significantly simplifies the complete measurement process
and reduces communications between the AP and the
MAX11800–MAX11803.
In autonomous mode, the MAX11800–MAX11803 use
combined commands to control and automate all
aspects of panel setup, measurements, and timing. See
the Operating Mode Configuration Register (0x0B) section for more details.
Direct Conversion Mode Operations
In direct conversion mode, the AP requests individual
panel setup and conversion operations or automated
SETUP
X
PANEL
NO
COMMAND
SETUP
Y
PANEL
NO
COMMAND
SETUP
Z
PANEL
combinations of measurements (X and Y, X and Y and
Z1, or X and Y and Z1 and Z2 combined). Unlike
autonomous conversion modes, the AP maintains control
over the initiation of panel setup, measurements events,
and the sampling frequency. Figure 8 shows the state
machine transitions for direct conversion mode.
Interrupt Modes
The MAX11800–MAX11803 support two direct conversion interrupt modes. The two direct conversion modes
are the continuous interrupt mode (CINT) and the edge
interrupt mode (EINT).
Continuous Interrupt Mode
In continuous interrupt mode, the panel returns to TDM
and idle. The current status of the panel is then sent
through TIRQ. The continuous interrupt mode is the
least efficient mode in current consumption for long
duration of touches. The power consumption is approximated by PTOUCH = VDD2/RPU. The power consumption levels observed when the panel is not touched is
limited by the junction leakage currents of the
MAX11800–MAX11803.
TOUCH
DETECT
X
DETECT
DONE AND
CONTINUOUS
AUX
ACQUIRE
Y
ACQUIRE
Z1
ACQUIRE
LAST
CONVERSION
Z2
ACQUIRE
DONE AND
CONTINUOUS
T
NO
ND
T A OUS
LAS TINU
N
CO
T
NO
ND
T A OUS
LAS TINU
N
CO
AVERAGE
CONVERSION
TIME IS UP
NO
CO T LA
NT ST
INU OR
OU
S
NO
COMMAND
NO
CO T LA
NT ST
INU OR
OU
S
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
AVERAGE
CONVERSION
LAST
CONVERSION
USER COMMAND
INTERNAL TRANSITION
TOUCHDETECT
FINE
PULLUP
TIME IS UP
Figure 8. State Machine Transitions (Direct Conversion Mode)
24
______________________________________________________________________________________
TOUCHDETECT
FINE
PULLUP
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Edge Interrupt Mode
When a touch is present on the panel in edge interrupt
mode, the MAX11800–MAX11803 return to an untimed
high-impedance mode once data tagging operations are
complete. In edge interrupt mode, the duration of a touch
is determined by the tags applied to the measurement
data. Data tagged as initial (00) or midpress (01) indicates
the user needs to continue to scan the panel until a
release is observed. In this state, there is no need to continue monitoring the touch status prior to the next requested measurement. If a panel touch is not present, data is
tagged as release (10) and the MAX11800–MAX11803
idle in TDM continuously, issuing an interrupt only when
the next panel touch is initiated.
The operation described in the preceding paragraph
makes the edge interrupt mode more efficient than the
continuous interrupt mode. However, the edge interrupt
mode requires continuous scanning of the panel until a
release (10) event is observed. Otherwise, the
MAX11800–MAX11803 do not idle in TDM and are not
able to recognize a change in touch status. New touches
are not recognized and new interrupts are not issued if a
release event is not detected before stopping the conversion sequence.
Table 6. Measurement and Event Tags
(Continuous Interrupt Mode)
MEASUREMENT
MTAG[3:2]
X
00
Y
01
Z1
10
Z2
11
EVENT
ETAG[1:0]
Touch (data valid)
00
N/A (not used)
01
No touch present (data
invalid)
Measurement in progress
(data invalid)
10
11
END OF TOUCH EVENT
BEGINNING OF TOUCH EVENT
PANEL
TIRQ
TDM
TDM
DCM SCAN
ETAG = 00
TDM
DCM SCAN
ETAG = 00
tAP
TDM
DCM SCAN
ETAG = 00
tSD
READBACK OPERATIONS ARE NOT SHOWN, BUT ARE EXECUTED DURING TDM PERIODS.
SCAN INTERVAL (tAP) IS CONTROLLED BY THE AP AND THE INITIATION OF DM SCAN EVENTS.
SCAN DURATION (tSD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.
Figure 9. Continuous Interrupt Mode (Direct Conversion Mode)
______________________________________________________________________________________
25
MAX11800–MAX11803
The MAX11800–MAX11803 idle in TDM. The TIRQ output
goes low when a touch is detected on the panel indicating to the AP that a touch is present and a measurement
operation starts.
The AP requests specific panel measurements through
the serial interface. TIRQ stays low during panel setup
and measurement operations. Once a measurement is
complete (with CONT = 0), the MAX11800–MAX11803
check for the continued presence of a touch on the
panel and tag the data accordingly (see Table 6). The
duration of this operation is programmable, specified in
the touch-detect pullup timing configuration register
(0x07). After the data is tagged, the data is available for
readback through the serial interface. The
MAX11800–MAX11803 return to TDM and return control
of TIRQ to the TDM circuitry. TIRQ stays low while a
touch remains present, indicating further measurements
are required, otherwise TIRQ goes high until a new touch
is observed.
Continuous interrupt mode (CINT) allows the complete
control over the measurement operations and direct observation of the touch status of the panel. Figure 9 shows the
polling of TIRQ when other functions share the TIRQ bus. In
the illustration of Figure 9, no ‘10’ event tag is observed
because the release occurs during a TDM period.
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
The EINT mode reduces TIRQ activity. During EINT, the
MAX11800–MAX11803 idle in a TDM. TIRQ goes low
when a new touch is detected on the panel. TIRQ stays
low for a fixed duration as specified in the configuration
register 0x01, indicating to the AP that a touch is present and measurements are required.
The AP requests specific panel setups and measurements through the serial interface using panel setup
and conversion commands after TIRQ goes low. Once
a measurement is complete (with CONT = 0), the
MAX11800–MAX11803 check for the continued presence of a touch and tag the data accordingly. See
Table 7. The duration of this operation is programmable, specified in the Touch-Detect Pullup Timing
Configuration Register (0x07) section. After the data is
tagged, it is available for readback through the serial
interface. The MAX11800–MAX11803 do not return to
TDM when the panel touch is still present (ETAG = 00,
01), but remain in an LPM awaiting further measurement commands. The devices return to TDM when the
panel touch is no longer present (ETAG = 10) and
return control of the TIRQ interrupt to the TDM circuitry
to await the next touch event.
After a touch is indicated, the AP must continue to issue
conversion commands until the touch is removed alerting the AP when the panel is released (by ETAG = 10).
The MAX11800–MAX11803 return to TDM and observe
the start of the next touch event. Panel commands
Table 7. Measurement and Event Tags
(Edge Interrupt Mode)
MEASUREMENT
MTAG[3:2]
X
00
Y
01
Z1
10
Z2
11
EVENT
ETAG[1:0]
Initial touch (data valid)
00
Midpress (data valid)
01
Release/no touch present
(data invalid)
10
Measurement in progress
(data invalid)
11
issued with CONT = 1 are not capable of fulfilling this
requirement.
The EINT mode provides the least interrupt activity and
the lowest power consumption. Use EINT mode for
general touch-screen applications and applications
requiring high resolution in space and time. When the
TIRQ bus is shared with other functions, poll the general status register (0x00) to detect the presence of an
interrupt. See Figure 10.
END OF TOUCH EVENT
BEGINNING OF TOUCH EVENT
PANEL
tIRQ
TIRQ
TDM
LPM
DCM SCAN
ETAG = 00
LPM
DCM SCAN
ETAG = 01
tAP
TDM
DCM SCAN
ETAG = 10
tSD
READBACK OPERATIONS ARE NOT SHOWN, BUT ARE EXECUTED DURING TDM PERIODS.
TIRQ DURATION (tIRQ) IS SPECIFIED BY THE GENERAL CONFIGURATION REGISTER (0x01).
SCAN INTERVAL (tAP) IS CONTROLLED BY THE AP AND THE INITIATION OF DM SCAN EVENTS.
SCAN DURATION (tSD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.
Figure 10. Edge Interrupt Mode (Direct Conversion Mode)
26
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
MAX11800–MAX11803
Table 8. Panel Setup Command Summary
HEX
R6
R5
R4
R3
R2
R1
R0
ACCESS
PAIRABLE
COMMAND
LENGTH
6xh
1
1
0
1
0
0
(1)
Write
No
8
X = panel setup
6xh
1
1
0
1
0
1
(1)
Write
No
8
Y = panel setup
6xh
1
1
0
1
1
0
(1)
Write
No
8
Z1 = panel setup
6xh
1
1
0
1
1
1
(1)
Write
No
8
Z2 = panel setup
Panel Setup Commands
Panel setup commands configure the touch panel prior to
a measurement. Panel setup commands allow the panel
to fully settle before performing a measurement. The
panel setup command summary is shown in Table 8. See
the register map in the Status and Configuration Registers
section for details on the panel setup timing options for X,
Y, Z1, and Z2 measurements.
The continuation bit (CONT) of the panel setup command programs the MAX11800–MAX11803 to maintain
the present panel setting at the end of the command
(CONT = 1). Panel setup commands assume a logical
progression to an appropriate measurement. For example, when the MAX11800–MAX11803 are in the X panel
setup mode, the devices can proceed to an X measurement mode only. The devices return to LPM when an
incompatible command follows a panel setup command. See Figure 11.
Panel Measurement Commands
A measurement command selects one of the four physical setup options: X, Y, Z1, or Z2. The panel measurement command summary is shown in Table 8.
All panel measurement commands include timed intervals to power up both the internal ADC and the panel
with programmable durations. The delayed conversion
time (tD_CV, delayed conversion configuration register
(0x06)) governs the time that the panel and the ADC
need to settle prior to the initiations of conversions. The
minimum delayed conversion time is 10μs, which is the
time the internal ADC needs to power up. If more settling time is required, increase the panel settling time
by delaying the conversion time or by adding an additional panel setup time (tPSU) using the panel setup timing configuration register (0x05). The advantage of
using a dedicated panel setup time is that the ADC
does not consume power during this interval. The
required panel setup time is a function of the panel
end-to-end resistance, the capacitance of the panel,
and any board-level components.
OPERATION
LPM
N
X PSU CMD
Y
X MEAS CMD
N
Y
N
Y PSU CMD
Y
Y MEAS CMD
N
Y
N
Z1 PSU CMD
Y
Z1 MEAS CMD
N
Y
N
Z2 PSU CMD
Y
Z2 MEAS CMD
N
Y
Figure 11. Command and Measurement Flow (DCM)
______________________________________________________________________________________
27
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Table 9. Panel Measurement Command Summary
HEX
R7
R6
R5
R4
R3
R2
R1
R0
(CONT)
ACCESS
PAIRABLE
COMMAND
LENGTH
7xh
0
1
1
1
0
0
0
(0)
Write
No
8
X, Y = combined command
measurement
7xh
0
1
1
1
0
0
1
(0)
Write
No
8
X, Y, Z1 = combined
command measurement
7xh
0
1
1
1
0
1
0
(0)
Write
No
8
X, Y, Z1, Z2 = combined
command measurement
7xh
0
1
1
1
0
1
1
(0)
Write
No
8
AUX = conversion
7xh
0
1
1
1
1
0
0
CONT
Write
No
8
X = measurement
7xh
0
1
1
1
1
0
1
CONT
Write
No
8
Y = measurement
7xh
0
1
1
1
1
1
0
CONT
Write
No
8
Z1 = measurement
7xh
0
1
1
1
1
1
1
CONT
Write
No
8
Z2 = measurement
When using a measurement command with CONT = 1 in
a direct conversion mode, the MAX11800–MAX11803
perform a data tagging operation at the conclusion of the
command. The devices remain in the requested setup
mode in preparation for the succeeding measurement.
The panel does not return to TDM/LPM and the interrupt
status is not modified as a result of a measurement command with CONT = 1 issued. See Figure 12.
Combined Commands
In direct conversion modes, the panel returns to a TDM
at the conclusion of a combined command and all data
are tagged accordingly. The MAX11800–
MAX11803 then idle in a low-power mode determined
by the interrupt mode selected. See Figure 13.
Auxiliary Measurement Command
The MAX11800–MAX11803 support measurement of an
auxiliary input using the internal ADC in direct conversion mode only. When programmed, the devices sam-
28
FUNCTION
ple and quantize the voltage at AUX using VDD as the
ADC reference. The MAX11800–MAX11803 store the
result in the same manner as X, Y, Z1, and Z2 measurements, but do not add data tagging. The devices also
support averaging functions. Auxiliary measurements
do not require any panel setup procedure. There is no
combined command which includes an auxiliary measurement. Register 0x0A specifies the configuration for
auxiliary measurements.
In CINT, the MAX11800–MAX11803 continue to monitor
for the touch status of the panel. The devices report any
change in touch status in real time during an auxiliary
measurement procedure.
When performing auxiliary measurements in edge
interrupt mode, the MAX11800–MAX11803 temporarily
suspend the panel touch monitoring. The devices notify the AP after the completion of the auxiliary measurement when a new touch occurs during the auxiliary
measurement.
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
MAX11800–MAX11803
PANEL SETUP COMMANDS (DIRECT CONVERSION ONLY)
SETTING IS MAINTAINED UNTIL NEXT COMMAND (FORCE CONT = 1).
PANEL SETUP (PSU) FOR X, Y, OR Z DRIVE
MEASUREMENT COMMANDS (DIRECT CONVERSION ONLY)
SINGLE CONVERSION WITH CONT = 1
SETUP
(tPSU + tD_CV)
ADC
CONVERSION
ADC
ACQUISITION
PSU
DATA IS LOGGED.
SETTING IS MAINTAINED UNTIL NEXT COMMAND (CONT = 1).
AVERAGED CONVERSION WITH CONT = 1
SETUP
(tPSU + tD_CV)
ADC
CONVERSIONi
ADC
ACQUISITIONi
PSU
AVERAGED DATA IS LOGGED.
SETTING IS MAINTAINED UNTIL NEXT COMMAND (CONT = 1).
NAVG
SINGLE CONVERSION WITH CONT = 0
SETUP
ADC
ACQ
ADC
CONV
PUR
(OPT)
PUF
DATA IS TAGGED AND LOGGED.
THE MAX11800–MAX11803 RETURN TO LPM OR TDM, ACCORDING TO IRQ MODE.
AVERAGED CONVERSION WITH CONT = 0
SETUP
ADC
ACQi
ADC
CONVi
PUR
(OPT)
PUF
AVERAGED DATA IS TAGGED AND LOGGED.
THE MAX11800–MAX11803 RETURN TO LPM OR TDM, ACCORDING TO IRQ MODE.
NAVG
Figure 12. Panel Setup and Measurement Commands
______________________________________________________________________________________
29
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
X AND Y COMMANDS
SINGLE CONVERSIONS
X
PSU
X
ACQ
X
CONV
DATA EVENT TAGGING
Y
PSU
Y
ACQ
Y
CONV
PUR
(OPT)
PUF
Y
PSU
Y
ACQ
Y
CONV
PUR
(OPT)
PUF
AVERAGED CONVERSIONS
X
PSU
X
ACQ
X
CONV
NAVGX
NAVGY
X, Y, AND Z1 COMMANDS
SINGLE CONVERSIONS
X
PSU
X
ACQ
X
CONV
Y
PSU
Y
ACQ
Y
CONV
Z1
PSU
Z1
ACQ
Z1
CONV
PUR
(OPT)
PUF
Y
PSU
Y
ACQ
Y
CONV
Z1
PSU
Z1
ACQ
Z1
CONV
PUR
(OPT)
PUF
AVERAGED CONVERSIONS
X
PSU
X
ACQ
X
CONV
NAVGY
NAVGX
NAVGZ1
X, Y, Z1, AND Z2 COMMANDS
SINGLE CONVERSIONS
X
PSU
X
ACQ
X
CONV
Y
PSU
Y
ACQ
Y
CONV
Z1
PSU
Z1
ACQ
Z1
CONV
Z2
ACQ
Z2
CONV
PUR
(OPT)
PUF
Y
PSU
Y
ACQ
Y
CONV
Z1
PSU
Z1
ACQ
Z1
CONV
Z2
ACQ
Z2
CONV
PUR
(OPT)
PUF
AVERAGED CONVERSIONS
X
PSU
X
ACQ
X
CONV
NAVGX
NAVGY
NAVGZ1
NAVGZ2
Figure 13. Combined Commands
30
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
transfers on the serial bus as well as generating fewer
interrupt requests. Figure 14 shows the state machine
transitions for autonomous conversion mode.
POWER
DOWN
AVERAGE
CONVERSION
LAST
CONVERSION
XY
TIME IS UP
TOUCHDETECT
FINE
PULLUP
TIME IS UP
TOUCH
DETECT
MO
DE
T
AS
LA
TL
SETUP
Z
PANEL
TIME IS UP
TIME IS UP
TIME IS UP
SETUP
Y
PANEL
Z1
ACQUIRE
AVERAGE
CONVERSION
LAST
CONVERSION
ST
LA
AS
TL
NO
T
AS
ST
LA
TL
T
NO
TIME IS UP
AVERAGE
CONVERSION
LAST
CONVERSION
AVERAGE
CONVERSION
LAST
CONVERSION
Z2
ACQUIRE
LA
T
AS
TL
ST
NO
TOUCH IS
PRESENT
SETUP
X
PANEL
Z2
Y
ACQUIRE
TOUCHDETECT
FINE
PULLUP
TOUCH
DETECT
Z1
ST
NO
TIME IS UP
TOUCHDETECT
ROUGH
PULLUP
NO
TOUCH
TOUCHDETECT
ROUGH
PULLUP
XY MODE
TIME IS UP
X
ACQUIRE
Figure 14. State Machine Transitions––Autonomous Conversion Mode
______________________________________________________________________________________
31
MAX11800–MAX11803
Autonomous Conversion Mode
The MAX11800/MAX11801 perform measurements
automatically and inform the AP when they are complete in autonomous conversion mode, reducing data
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Measurement Operations
In autonomous conversion, the MAX11800/MAX11801
idle in TDM until a touch event occurs. The
MAX11800/MAX11801 begin an automated sequence
of measurements as defined by the configuration register 0x08h.
The MAX11800/MAX11801 tag and log the data into the
FIFO once a measurement is taken. If a touch is still present, the devices continue to idle in a LPM until the time,
as set by the configuration settings, expires. If no touch is
present at the expiration of the time set by the configuration settings, the MAX11800/MAX11801 return to TDM to
await the next panel touch.
All measurement operations occur without any intervention from the AP. The MAX11800/MAX11801 issue interrupts when new data is available in the internal FIFO. The
device clears the interrupt when all data is read back.
The AP controls the readback of measurement data as
the data becomes available.
Combined Commands
In autonomous conversion mode, the MAX11800/
MAX11801 automatically perform the combined command defined in the configuration register. The devices
continuously scan for panel touch events. Between
scans, the devices idle in a low-power mode according
to the present touch status.
Clear-on-Read Interrupt Mode
The MAX11800/MAX11801 control the progression
through modes in clear-on-read mode. When the panel
touch is present, the MAX11800/MAX11801 return to a
timed high-impedance LPM to minimize current, after
the data tagging operations are complete. The
MAX11800/MAX11801 idle in LPM until it is time to perform the next required scan, determined by the configuration register settings. When a touch is not present at
the end of a measurement, the device returns to idle in
TDM. In TDM, the device waits until a touch is detected
before initiating another set of autonomous measurements.
The MAX11800/MAX11801 adopt a clear-on-interrupt
protocol (CORINT) when in autonomous conversion
mode. Between touch events, the devices idle in a lowpower TDM state. Upon detection of a touch, the
devices begin a sequence of automated measurements. Each time a qualifying measurement is completed, the data for that measurement is written to the
internal FIFO. Qualifying measurements are measurements that indicate the beginning and end of a touch
event, which meet aperture requirements (see the
Aperture Range Requirements section).
TIRQ issues an interrupt once a qualifying measurement is completed and logged into the FIFO indicating
that new data is available for the AP to read back. The
MAX11800/MAX11801 continue to perform measurements as required by the configuration settings.
Program the AP to service the interrupt immediately to
avoid a FIFO overflow and loss of data. TIRQ remains
asserted until all unread FIFO data has been read back
to the AP. The AP confirms that readback is complete
either by monitoring TIRQ or by monitoring the data
event tags embedded in the data for end-of-FIFO.
(ETAG = 11b). See Figure 15.
BEGINNING OF TOUCH EVENT
END OF TOUCH EVENT
PANEL
DATA WRITTEN TO FIFO,
INTERRUPT ISSUED
AP READBACK,
INTERRUPT CLEARED
INTERRUPT IS HELD PENDING
AP READBACK (FIFO STORES DATA)
TIRQ
SCAN
BLOCK
TDM
LPM
ACM SCAN
ETAG = 00
tINIT
tSD
ACM SCAN
ETAG = 01
LPM
ACM SCAN
ETAG = 10
TDM
tSP
READBACK OPERATIONS ARE NOT SHOWN, INDICATED BY THE CLEARING OF THE AP-INITIATED INTERRUPT.
WAIT TIME BETWEEN TOUCH DETECTION AND INITIAL SCAN (tINIT) IS SPECIFIED BY CONFIGURATION SETTINGS.
SCAN DURATION (tSD) IS A FUNCTION OF THE SCAN TYPE AND CONFIGURATION SETTINGS.
SCAN PERIOD (tSP) IS CONTROLLED BY CONFIGURATION SETTINGS.
Figure 15. Clear-on-Read Interrupt Operation
32
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
FIFO Memory
The MAX11800/MAX11801 include an internal FIFO to
store scan block results for readback through the AP.
Each scan block result contains complete data for all
measurements requested by the scan type (X, Y; or X,
Y, Z1; or X, Y, Z1, Z2). The depth of each scan data
block ranges from 32 bits (X, Y mode) to 48 bits (X, Y,
Z1 mode) or 64 bits (X, Y, Z1, and Z2 mode).
The internal FIFO stores up to 16 complete scan
blocks, a total of 1024 bits. Regularly service the FIFO
to prevent overflow conditions. In the event of an overflow, the FIFO ceases to write new data until the old
data is read or cleared. Avoid overflow to prevent data
loss and unreliable behavior.
Check the general status register (0x00) and the FIFO
overflow bit to determine if the FIFO is in overflow. The
FIFO overflow bit asserts when a data overflow occurs.
See the Clearing FIFO section.
Clearing FIFO
Write to the operating mode configuration register (0x0B)
to clear the FIFO. Modifying the contents of the register is
not necessary as any write operation to this register location clears the FIFO and the interrupt TIRQ (if present).
The FIFO completely clears when autonomous conversions halt and the MAX11800/MAX11801 transition to
direct conversion mode. The FIFO also clears on transitions from direct conversion mode to autonomous mode.
FIFO Data Block Readback Structure
Table 10 illustrates the scan data block structure within
the FIFO for each scan type. Block boundaries are indicated by bold lines. Numeric subscripts denote the sample order when the data was taken. Readback proceeds
from top to bottom. FIFO blocks are written as a complete unit with an interrupt issued only after all required
block measurements are complete and data is tagged.
A FIFO data block consists of 2 to 4 FIFO data words.
Table 10. FIFO Data Block Structure
2-WORD BLOCK
(X, Y)
X1 MSB
3-WORD BLOCK
(X, Y, Z1)
4-WORD BLOCK
(X, Y, Z1, Z2)
X1 MSB
X1 MSB
X1 LSB
X1 LSB
X1 LSB
Y1 MSB
Y1 MSB
Y1 MSB
Y1 LSB
Y1 LSB
Y1 LSB
X2 MSB
Z11 MSB
Z11 MSB
X2 LSB
Z11 LSB
Z11 LSB
Y2 MSB
X2 MSB
Z21 MSB
Y2 LSB
X2 LSB
Z21 LSB
X3 MSB
Y2 MSB
X2 MSB
X3 LSB
Y2 LSB
X2 LSB
Y3MSB
Z22 MSB
Y2 MSB
Y3 LSB
Z22 LSB
X4 MSB
Y2 LSB
.
Z12 MSB
X4 LSB
.
Z12 LSB
Y4 MSB
.
Z22 MSB
Y4 LSB
.
Z22 LSB
______________________________________________________________________________________
33
MAX11800–MAX11803
Delayed Touch Detection During Mode Transitions
The MAX11800/MAX11801 support a low-power powerdown mode suspending all touch-screen activity and
the panel is not driven. In this mode, the
MAX11800/MAX11801 is unable to detect a touch.
When commanded to transition from PWRDN to any
normal mode of operation, the MAX11800/MAX11801
go through a PUR/PUF sequence prior to observing the
panel touch status, minimizing the occurrence of interrupts issued by false touches caused by the initial state
of panel capacitances.
In addition, when commanded to transition between
normal operating modes, the MAX11800/MAX11801
clear any existing interrupts and go through the
PUR/PUF sequence prior to observing the current panel
touch status.
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
FIFO Data Word Structure
Table 11 shows a 16-bit data word (MSB byte + LSB
byte). Each data word consists of 12 bits of position
data, mapped to locations [15:4]. Eight-bit measurement data are left-adjusted and mapped to locations
[15:8] and followed by four trailing zeros. Table 12
shows a 2-bit measurement tag indicating the measurement type (X, Y, Z1, or Z2), appended in locations [3:2].
Table 13 shows a 2-bit event tag indicating where the
sample occurs within a touch event (initial, midpress, or
release) in locations [1:0].
All data for a given scan operation is tagged according
to the touch status observed at the end of the scan
block measurement operations. For example, if a
requested X, Y, Z1, Z2 scan block contains a release
event, all the data words are tagged 10 before being
written to the FIFO.
An event tag of 11 indicates that the data readback
operation reaches the end of the current FIFO data log
(end of file marker) and there is no unread data in the
FIFO. Terminate the readback operation to await the
next interrupt. Ignore all data with the 11 event tag.
Block Readback Operations
The MAX11800/MAX11801 do not support partial block
readback operations. Each readback operation loads
an entire scan block result (32, 48, or 64 bits) into a
temporary location for serial readback. A scan block is
marked as read in the FIFO once a scan block result is
loaded, freeing the memory space for the subsequent
measurements. Once initiated, the AP must complete
the full readback cycle for the block requested or the
unread portions of the block data is lost.
Clearing Interrupt
The FIFO is only used in the autonomous mode with the
clear-on-read interrupt. The interrupt is cleared only
when the newest data block currently available in the
FIFO is loaded for readback. The interrupt does not
clear if there is any unread data block remaining in the
FIFO once a scan block result is loaded. The FIFO does
not check for partial block readbacks. Once the last
available FIFO data block is loaded for readback, the
interrupt clears regardless of whether the readback
operation for that block is complete.
Aperture Modes* and Options
The aperture modes available with the MAX11800/
MAX11801 implement spatial filtering. The MAX11800/
MAX11801 contain the required logic to examine panel
measurement data and determine if the data meets the
aperture requirements to be written to the FIFO. Aperture
testing decreases the number of entries in the FIFO to
the minimum required to implement the intended application. The elimination of extraneous FIFO data events
reduces activity on the TIRQ line, serial bus, and minimizes AP overhead. The contents in the FIFO are not
necessarily linearly sampled in time when the device is in
aperture mode.
Aperture Range Requirements
Program the aperture range requirements for both X
and Y through register 0x0B. Range requirements are
expressed as distance, in position LSBs. The blanking
aperture extends from the initial touch position, both
±ΔX and ±ΔY with 12-bit resolution (1 LSB = 1/4096 of
the corresponding screen dimension). An aperture setting of 0x00 effectively disables aperture checking with
all measurement data logged to the FIFO. Apertures
are specified in a power-of-two format: ΔX = 2APRX[3:0]-1
and ΔY = 2APRY[3:0]-1.
Table 11. FIFO Data Word Structure
INDEX
15
Byte
14
13
12
11
10
9
8
7
6
5
MSB Byte
4
3
2
1
0
LSB Byte
12-Bit Content
Position MSBs
Position LSBs
Measure
Event
8-Bit Content
Position Data
Trailing Zeros
Measure
Event
Table 12. FIFO Data Measurement Tags
Table 13. FIFO Event Tags
EVENT
TAG[3:2]
X
00
Initial touch
Y
01
Midpress
01
Z1
10
Release (data invalid)
10
Z2
11
End of file indicator
(FIFO data invalid)
11
*Patented feature.
34
TAG[1:0]
MEASUREMENT
______________________________________________________________________________________
00
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
0001 = 2(1-1) LSB = ±1 LSB
0010 = 2(2-1) LSB = ±2 LSB
0011 = 2(3-1) LSB = ±4 LSB
…
1001 = 2(9-1) LSB = ±256 LSB (1/16 of the screen in
each direction)
1010 = 2(10-1) LSB = ±512 LSB (1/8 of the screen in
each direction)
1011 = 2(11-1) LSB = ±1024 LSB (1/4 of the screen in
each direction)
1100 = 2(12-1) LSB = ±2048 LSB (1/2 of the screen in
each direction)
1101 to 1111 = aperture checking disabled
FIFO Aperture Criteria
In autonomous mode with aperture engaged, new data
is written to the FIFO, and an interrupt is issued when
the following conditions occur (aperture mode is not
available in direct conversion mode).
New Panel Touch Initiated
The FIFO updates and issues an interrupt when a new
touch is observed on the panel (data tag = 00). This
event occurs regardless of the current aperture setting
and the previous touch location so that multiple presses
in the same location can be observed and registered.
Continuous Panel Touch Terminated
The FIFO updates and issues an interrupt when a continuous panel touch is terminated (data tag = 10). This
event occurs regardless of the current aperture setting
and the previous continuous touch location(s) so that
multiple presses in the same location can be observed
and registered.
Continuous Panel Touch
Measurement Meets Aperture Criteria
The MAX11800/MAX11801 log the measurement data
to the FIFO and issue an interrupt when a measurement
during a continuous panel touch (event tag = 01) meets
the aperture criteria (i.e., lies on or outside the aperture
boundary). This event occurs when the point of contact
is dragged across the touch screen. Only the ΔX or ΔY
aperture criteria need to be met and a greater than or
equal to qualification criterion is applied. If the change
in X position or change in Y position exceeds the aperture criteria, then an interrupt is generated.
Applications Information
Using Aperture Mode
The MAX11800/MAX11801 accommodate touch-panel
applications where limited resolution in both time and
space can be traded off for reduced microprocessor
activity. A simulated keypad is an example of an application where autonomous conversions with aperture
checking yield an efficient solution.
The AP determines the durations of touch-screen
presses. An issuance of TIRQ interrupts accompanies
all FIFO events. The interrupts clear when all existing
data is read back by the AP, allowing the AP to correctly interpret held panel data.
The FIFO updates immediately when a new touch event
is detected. The system assumes that the panel touch is
continuous after the AP receives the interrupt. The
MAX11800/MAX11801 continue to scan the panel at the
user-programmed sample rate. The FIFO updates when
the measurement data shows that the panel touch location moves (i.e., a measurement exceeds either of the
selected aperture ranges). The FIFO also updates upon
detection of a panel release. The AP determines the
duration of the press by observing the time between the
leading edge of the touch (tag 00) and the release edge
of the touch (tag 10). All midpress data (tag 01) are interpreted as part of a dragged touch event.
All valid touch events log two data points into the FIFO:
an initial data point at the beginning of the touch (tag
00) and a release data point at the termination of the
touch (tag 10). Discard release edge position data as
invalid as the MAX11800/MAX11801 cannot determine
at which point in the ADC conversion cycle the panel is
released during the measurement operation. If the
release occurs while the ADC is actively sampling the
panel, the results are invalid. Only initial and midpress
position data are reliable.
Any touch event too short in duration to log both initial
and release data points is recorded in the FIFO as a
release (tag 10) and discarded as a glitch event.
Measuring durations of panel touches becomes
impractical when the AP services the MAX11800/
MAX11801 at lower than the operating speed of the
devices and the panel combined. The AP cannot time
the duration between panel touches when both the initial and release data points can be logged before the
initial interrupt is serviced. Do not allow the FIFO to
overflow as touch information can be lost and the FIFO
content becomes invalid.
______________________________________________________________________________________
35
MAX11800–MAX11803
For example:
0000 = 2-1 LSB = aperture checking disabled
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
that meet aperture requirements are enumerated and
are shown with the corresponding aperture ranges.
Positions 6 and 7 show a subsequent momentary press
event.
Figure 16 shows the anticipated interrupt waveforms in
several operating modes. The first waveform shows
interrupt operation assuming that aperture mode is
enabled (with ΔX = ΔY = 4 LSBs), assuming that the AP
service interrupts at a frequency faster than the selected TSC sample rate. Each qualifying sample induces a
FIFO event and an interrupt pulse as shown. Timing
between FIFO events can be timed by the AP to determine duration information. Table 14 shows the readback data assuming that the FIFO does not fill up.
When the MAX11800/MAX11801 operate in autonomous
conversion mode with low or no aperture ranges, the
FIFO and interrupt activity occur frequently with the AP
servicing the devices frequently to avoid loss of data
due to limited FIFO depth. For this reason, do not perform autonomous conversion for applications where a
high resolution in either space or time is required. Use
direct conversion mode when requiring a high resolution in either space or time.
Examples of Using Aperture Mode
Figure 16 shows an example of a touch sequence. A
dragged touch sequence is initiated at position 1 and
continues through to position 5. While multiple samples
are taken during this sequence, only those samples
ONE DRAG EVENT (1:5)
AND ONE PRESS EVENT (6:7) SECOND
RELEASE
DRAG
7
PANEL TOUCH SPATIAL WAVEFORM
16
APER1
6
SECOND
TOUCH
APER2
12
INITIAL
TOUCH
DRAG
1
APER6
2
8
5
4
DRAG
INITIAL
RELEASE
3
DRAG
4
APER4
APER3
0
4
8
12
16
20
24
INTERRUPT TIMING WAVEFORM 1 (ASSUMING FREQUENT SERVICING EVENTS WITH APERTURE MODE ENABLED)
1
2
3
4
5
6
7
INTERRUPT TIMING WAVEFORM 2 (ASSUMING FREQUENT SERVICING EVENTS WITH APERTURE MODE DISABLED)
1
2
3
4
5
6
7
INTERRUPT TIMING WAVEFORM 3 (ASSUMING INFREQUENT SERVICING EVENTS)
(1) IRQ ISSUED
(SERVICED) IRQ RELEASED
NOTE: POSITION 5 IS LOGGED EVEN THOUGH POSITION 5 APPEARS IN APER4 BECAUSE POSITION 5 IS A RELEASE DATA POINT.
IT IS THE SAME FOR POSITION 7. IF THE POSITION 6 TOUCH EVENT INITIATES WITHIN THE FINAL APERTURE FROM THE
PREVIOUS EVENT (APER4), POSITION 6 IS LOGGED AS AN INITIAL TOUCH EVENT.
Figure 16. Aperture Usage Example Waveforms
36
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
at the programmed sample rate. Table 15 lists the readback data assuming the FIFO does not fill up.
The third waveform in Figure 16 shows an interrupt operation assuming that the MAX11800/MAX11801 are infrequently serviced. Ensure that the FIFO does not overflow.
No duration information is available at resolutions below
the servicing rate. Either the set of data shown in Table
14 or the set shown in Table 15 appears in the FIFO
when read, depending on the aperture setting.
Table 14. Readback and FIFO Contents with Aperture Mode Enabled
SAMPLE
X
Y
TAG
1
7
11
00
Initial event (beginning of first touch)
COMMENT
2
11
9
01
Midpress event
3
13
5
01
Midpress event
4
17
7
01
Midpress event (last valid position data)
5
19
6
10
Release event (end of first touch, ignore position data)
6
22
14
00
Initial event (beginning of second touch)
7
23
15
10
Release event (end of second touch, ignore position data)
Table 15. Readback and FIFO Contents with Aperture Mode Disabled
SAMPLE
X
Y
TAG
1
7
11
00
Initial event (beginning of first touch)
COMMENT
1a
9
10
01
Midpress event
2
11
9
01
Midpress event
2a
12
8
01
Midpress event
2b
13
7
01
Midpress event
2c
13
6
01
Midpress event
3
13
5
01
Midpress event
3a
15
6
01
Midpress event
4
17
7
01
Midpress event (last valid position data)
5
19
6
10
Release event (end of first touch, ignore position data)
6
22
14
00
Initial event (beginning of second touch)
7
23
15
10
Release event (end of second touch, ignore position data)
______________________________________________________________________________________
37
MAX11800–MAX11803
The second waveform shows an interrupt operation
assuming that aperture mode is disabled (or that ΔX =
ΔY = 0 LSB), assuming that the AP service interrupts at
a frequency faster than the selected TSC sample rate.
Every sample induces a FIFO event and an interrupt
pulse as shown. The interrupt waveform is significantly
busier than that shown in the first waveform. Duration
information can now be directly determined from the
FIFO samples since each sample is logged and occurs
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
SPI Configuration Register Write
(MAX11800/MAX11802)
Figure 17 shows the supported write operation
sequence for the MAX11800/MAX11802. A single configuration register can be written in a 2-byte operation,
composed of a target register address (A[6:0], plus a
write mode indicator bit) followed by data to be written
to the target register (D[7:0]).
During write sequences, the DOUT line is not accessed
by the SPI. DOUT remains high impedance throughout
the command. Using the optional bus holder, the DOUT
line retains the previous value unless altered by a
device sharing the bus.
The MAX11800/MAX11802 SPI interface supports multiple register write operations within a single sequence
as shown in Figure 18. By repeating the address plus
data byte pairs (in write mode), an unlimited number of
registers can be written in a single transfer. Do not permit to combine write and read operations within the
same SPI sequence.
SPI Communication Sequence
(MAX11800/MAX11802)
The SPI interface consists of three inputs, DIN, DCLK,
CS, and one output, DOUT. A logic-high on CS disables the MAX11800/MAX11802 digital interface and
places DOUT in a high-impedance state. Pulling CS low
enables the MAX11800/MAX11802 digital interface. The
MAX11800/MAX11802 provide two possible implementations of SPI instructions. In rising-edge-driven operations, the devices are able to run at maximum clock
speeds. Carefully consider the hold time requirements
of the MAX11800/MAX11802 and minimize board skew
contributions when running the MAX11800/MAX11802
at maximum clock speed. In falling-edge-driven operations, the device is less sensitive to board skew contributions, but slower clock speeds are required to meet
the MAX11800/MAX11802 setup time requirements. For
the MAX11800/MAX11802, read patterns output data is
either latched on the rising edge running at maximum
clock rates or on the falling edges running at reduced
clock rates.
CS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
SCLK
DIN
A6
A5
A4
A3
A2
A1
A0
Wb
D7
D6
D5
D4
D3
D2
D1
D0
Figure 17. SPI Single Configuration Register Write Sequence
CS
1
7
9
17
23
25
32
SCLK
DIN
An [6:0]
Dn [7:0]
Am [6:0]
Dm [7:0]
Figure 18. SPI Multiple Configuration Register Write Sequence
38
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
crement is supported, the next register location is read
back. If not, the last valid register location is read back
(see the Command and Register Map section for the
autoincrement attributes of each register). The following
example shows a valid sequence for the readback of
three register locations (Di through Di+2).
The autoincrement reads only the X, Y, Z1, Z2, and AUX
result registers preventing inadvertent readback of unrelated or reserved data locations. For example, if beginning at the XMSB register, a user can cycle through the
XLSB register to the YMSB register and so forth up to the
AUXLSB register. The MAX11800/MAX11802 do not
autoincrement beyond the AUXLSB register. If clock
cycles continue to be given, the AUXLSB register readback is repeated.
The FIFO register does not autoincrement, which allows
multiple readbacks of the same location. This allows the
access of multiple FIFO memory blocks with a single read
operation. When reading back FIFO registers, data management is handled in blocks not bytes. As a result, when
an SPI read operation supplies at least one cycle of readback of the first byte of a FIFO block, the entire block is
marked as read, regardless of whether the block or even
byte readback is run to completion.
To illustrate, assume the MAX11800 is in autonomous
mode performing XY conversions and a FIFO readback
is requested starting at register 0x50. Clock cycles 9 to
40 are required to complete the readback of the first
available FIFO blocki = {XMSBi, XLSBi, YMSBi, YLSBi}
with the device updating in response to the 8th to 39th
clock rising edges. The host processor can complete
the readback data latching of YLSBi[0] either on the
39th falling edge or the 40th rising edge. To support a
continued readback of further FIFO blocks, the device
updates the DOUT line to XMSBi+1[7] in response to the
40th clock rising edge (though blocki+1 is not marked
as read). If the AP supplies a 42nd clock rising edge,
the FIFO blocki+1, if present, is marked as read, regardless of whether any further clock cycles are provided.
CS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
SCLK
DIN
A6
A5
A4
A3
A2
A1
A0
R
D7
DOUT
D6
D5
D4
D3
D2
D1
D0
S
Figure 19. SPI Single-Byte Register Read Sequence
______________________________________________________________________________________
39
MAX11800–MAX11803
SPI Configuration or
Result Register Read (MAX11800/MAX11802)
Figure 19 shows the read operation sequence for the
MAX11800/MAX11802. A single configuration register
can be read back in a 2-byte operation, composed of a
requested register address (A[6:0], plus a read mode
indicator bit) followed by the data contents from that register (D[7:0]).
During read operations, the SPI takes control of the DOUT
line following the eight SCLK rising edge. The SPI retains
control of the DOUT line until CS rises, terminating the
operation. To support multiple register readback operations, data continues to be ported following the 16th rising
clock edge. For single-byte transfers, this sub-bit information can be ignored, shown as S, in Figure 19.
The DOUT output on the MAX11800/MAX11802 includes
an optional bus holder to prevent the DOUT line from
maintaining an indeterminate state when vacated by the
device in the absence of an external bus pullup or bus
sharing devices. The bus holder is designed not to interfere with other drivers sharing the DOUT line and holds
the last valid state of the line, regardless of source.
Disable the bus holder when not needed.
The MAX11800/MAX11802 support the combination of
the DIN and DOUT lines. To avoid data contention and
possible high current states, the master device must relinquish control of the combined line at the 8th clock rising
edge, allowing the MAX11800/MAX11802 to access the
line through the end of the sequence. This is terminated
on the rising edge of CS. See the SPI Timing
Characteristics for relevant details.
The MAX11800/MAX11802 also support multiple register
readback operations using a single command. The protocol requires the user to supply an initial starting register
location, followed by an unlimited number of clock pulses
for data readback.
The first data read back is from the start register. The
MAX11800/MAX11802 internal autoincrement counter
manages the data readback in later cycles. If autoin-
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
SPI Conversion Command (MAX11800/MAX11802)
The sequence below shows the required command format for issuing conversion requests. A conversion
request cannot be paired with multiple commands or
instructions. Any conversion command issued while
previous commands are being executed is ignored.
ically a microcontroller) initiates data transfer on the
bus and generates SCL. The I2C device address is
10010xx; the last 2 bits of the I2C address are userconfigurable through the address inputs A[1:0].
I2C Configuration Register Write
(MAX11801/MAX11803)
Repeat the register address plus data pairs (byte 2 and
byte 3 in Figures 21, 22, and 23) to perform multiple
register writes. There is no limit to the number of registers written with a single command. For example, the
I2C master can perform multiple register writes to set up
all required conversion options, and then issue a separate I2C command to start a conversion process.
I2C-Supported Sequence
(MAX11801/MAX11803)
The MAX11801/MAX11803 feature an I2C-compatible,
2-wire serial interface consisting of a bidirectional serial
data line (SDA) and a serial clock line (SCL). SDA and
SCL facilitate bidirectional communication between the
MAX11801/MAX11803 and the master. The master (typCS
1
7
8
9
16
17
24
25
32
SCLK
Ai[6:0]
DIN
Di[7:0]
DOUT
Di+1[7:0]
S
Di+2[7:0]
Figure 20. SPI Multiple-Byte Register Read Sequence
CS
1
2
3
4
5
6
7
8
SCLK
DIN
A6
A5
A4
A3
A2
A1
A0
Wb
Figure 21. SPI Conversion Command
WRITE ADDRESS
BYTE 1: DEVICE ADDRESS
START
SDA
1
0
0
1
0
A1
WRITE REGISTER NUMBER
BYTE 2: FIRST REG NUMBER = N
A0
W
A
N
N
N
N
N
N
WRITE DATA
BYTE 3: REG(N)[7:0] DATA
N
N
A
D
D
D
D
D
D
STOP
D
D
A
SCL
Figure 22. I2C Single Register Write Sequence
SDA
1
0
0
1
0
A1 A0 W
WRITE DATA
BYTE 3: REG(N)[7:0] DATA
WRITE REGISTER NUMBER
BYTE 2: REG NUMBER = N
WRITE ADDRESS
BYTE 1: DEVICE ADDRESS
START
A
N
N
N
N
N
N
N
N
A
D
D
D
D
D
D
D
WRITE DATA
BYTE 5: REG(Z)[7:0] DATA
WRITE REGISTER NUMBER
BYTE 4: REG NUMBER = Z
D
A
Z
Z
Z
Z
Z
Z
Z
Z
A
D
D
D
D
SCL
Figure 23. I2C Multiple Register Write Sequence
40
______________________________________________________________________________________
D
D
D
STOP
D
A
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
SDA
WRITE REGISTER START NUMBER
BYTE 2: FIRST REG NUMBER = N
WRITE ADDRESS
BYTE 1: DEVICE ADDRESS
START
1
0
0
1
0
A1 A0 W
A
N
N
N
N
N
N
N
WRITE ADDRESS
BYTE 3: DEVICE ADDRESS
REPEATED
START
A
N
The MAX11801/MAX11803 support several streamlined
readback behavior to significantly improve data transfer
efficiency. Using the streamlined readback sequence
shown in Figure 25, data readback can commence following an assumed progression. Disable the streamlined readback feature to allow full readback sequence.
• Resumed Read Operations (MAX11801/
MAX11803)
When readback operations are suspended and later
resume from the current (incremented) register location, it is not necessary to supply the initial device
address and register start sequence. Begin the readback portion of the command following the streamlined
sequence shown in Figure 25 to allow more efficient
data transfer.
For example, if the user accesses the FIFO register
(MAX11801), which does not autoincrement, and reads
several observations and then stops and resumes the
readback operation at a later time, the user only needs
to issue the streamlined readback sequence to continue to gather observations from the FIFO. Once the
device is placed in autonomous mode, the user only
needs to issue the full readback sequence once for the
initial FIFO access. Then streamlined read access to
the device resumes at the FIFO location, unless an
intervening command is issued as shown in Figure 25.
Similarly, when reading back result registers, begin with
XMSB and autoincrement to XLSB, then stop. When
readback resumes by the issuance of the streamlined
readback sequence, data readback commences from
the YMSB location.
1
0
0
1
READ DATA
BYTE 4: REG(N)[7:0] DATA
0 A1 A0 R
A
D
D
D
D
D
D
D
READ DATA
READ DATA (LAST BYTE)
D
ADDITONAL
SEQUENTIAL READ
DATA BYTES
A
SCL
D
D
D
D
D
D
D
STOP
D ~A
ACKNOWLEDGE GENERATED BY I2C MASTER
ACKNOWLEDGE GENERATED BY MAX11801/MAX11803
Figure 24. I2C Multiple Register Read Sequence
WRITE ADDRESS
BYTE 3: DEVICE ADDRESS
START
READ DATA
READ DATA
BYTE 4: REG(N)[7:0] DATA
READ DATA (LAST BYTE)
SDA
1
0
0
1
0
A1 A0 R
A
D
D
D
D
D
SCL
ACKNOWLEDGE GENERATED BY MAX11801/MAX11803
D
D
D
A
ADDITONAL
SEQUENTIAL READ
DATA BYTES
D
D
D
D
D
D
D
STOP
D
~A
ACKNOWLEDGE GENERATED BY I2C MASTER
Figure 25. I2C Streamlined Register Read Sequence
______________________________________________________________________________________
41
MAX11800–MAX11803
• Streamlined I 2C Read Operations (MAX11801/
MAX11803)
I2C Configuration or Result Register Read
(MAX11801/MAX11803)
The read sequence does not limit the number of bytes to
be read. The internal register counter keeps incrementing as additional bytes are requested. The first byte out
is Reg(N) as shown in Figure 24. The next byte out is
Reg(N+1). The next byte out is Reg(N+2), and so on.
The programmer needs to keep track of the incremented
register address. Acknowledge pulses from the master
are not required to autoincrement the internal register
location. The internal register location updates on each
byte. See the Command and Register Map section for
details governing the incrementing of register addresses.
The autoincrement reads only the X, Y, Z1, Z2, and
AUX result registers preventing inadvertent readback of
unrelated or reserved data locations. For example, if
beginning at the XMSB register, a user can cycle
through the XLSB register to the YMSB register and so
forth up to the AUXLSB register. The MAX11801/
MAX11803 do not autoincrement beyond the AUXLSB
register. If clock cycles continue to be given, the
AUXLSB register readback is repeated.
The FIFO (MAX11801) register does not autoincrement,
which allows multiple readbacks of the same location.
This allows the access to multiple FIFO memory blocks
with a single read operation. When reading back FIFO
registers, data management is handled in blocks not
bytes. As a result, when an I2C read operation supplies
at least one cycle for readback of the first byte of a FIFO
block, the entire block is marked as read. This is regardless of whether the block or even byte readback is run
to completion.
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
• Direct Conversion Read Operations (MAX11801/
MAX11803)
are being executed is ignored and the readback target
register is not modified.
In direct conversion mode, commands automatically
set the readback target register and streamline data
gathering. See the Command and Register Maps section for specific details for all such commands. The
MAX11801/MAX11803 automatically set the default
readback register to the XMSB location when a command requesting is received and a XY combined measurement is received. If the XY command is issued and
allowed to complete, the device can then be followed
directly by a streamlined read sequence and data
readback commences from the XMSB register.
Accepted direct conversion commands always modify
the current internal register location and effectively
override the resumed readback behaviors and any register settings made in response to previously completed direct conversion commands.
• Read Operations Following Write Operations
(MAX11801/MAX11803)
Data readback commences from the last written register
location when the streamlined readback sequence is
issued following a configuration write operation. When
modifying the contents of the operating mode configuration register (0x0B) using a write sequence, then issuing
a streamlined readback sequence, the contents of register 0x0B are provided. Register write operations always
modify the current internal register location and effectively
override the resumed readback behaviors.
Command and Register Map
The command map consists of the user-configuration registers (read/write), TSC data readback commands (read
only), and TSC panel setup and conversion commands
(write only).
User-Accessible Registers
There are six blocks of user-accessible registers and
commands that control all operations of the
MAX11800–MAX11803. The register blocks and commands consist of the following:
1) Status and Configuration Registers: 00h to 0Bh
• Sets modes of operation––ACM or DCM
• Settings to accommodate various panel sizes
(panel time constant)
• Averaging and noise settings
• Measurement resolution
• Auxiliary settings
• General part status reporting
2) FIFO Data Readback Command: 50h
• Autonomous conversion mode only (MAX11800/
MAX11801)
• Allows reading FIFO contents when operating in
ACM
3) Data Readback Commands: 52h to 5Bh
I2C Conversion Command (MAX11801/MAX11803)
Figure 26 shows the required command format for issuing conversion requests. A conversion request cannot
be paired with multiple commands or instructions. Any
conversion command issued while previous commands
• Allows reading measurement results when in DCM
WRITE ADDRESS
BYTE 1: DEVICE ADDRESS
START
SDA
• Direct conversion mode only (MAX11800/
MAX11802)
1
0
0
1
0
A1
STOP
CONVERSION COMMAND
A0
W
A
N
N
N
N
N
N
N
N
A
SCL
Figure 26. I2C Conversion Command
42
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
position. For I2C, the protocol is always 8-bit byte followed by an acknowledge bit, for a total of 9 bits. The
MSB in I2C format is always 0. In write mode, for I2C,
the MSB is ignored internal to the MAX11800–
MAX11803, so setting it to 0 or 1 has no effect.
Status and Configuration Registers
The status and configuration registers are located in
block 0x00 to 0x0B. See Table 18. All user-configuration register write mode operations are pairable within
the SPI/I2C interface. Multiple locations can be written
under a single instruction with a register byte followed
by a data. All user-configuration read-mode operations
support autoincrement. For example, if location 0x00 is
read back and more clock pulses are issued, readback
will proceed through location 0x01 and so forth. The
user should set all configuration registers to the desired
values before issuing direct conversion operations or
placing MAX11800/MAX11801 in autonomous mode.
The commands to read or write the user-accessible
registers are always the same. However, the data format varies based on whether using an SPI or I2C interface. Tables 16 and 17 show the differences between
SPI and I2C protocols. For SPI, the R/W bit is embedded in the 8-bit byte and always occupies the LSB
Table 16. SPI Command and Data Format: 8 Bits
BYTE
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
R6
R5
R4
R3
R2
R1
R0
(CONT)
R/W
Command or Data
1/0
Table 17. I2C Command and Data Format: 8 Bits Plus ACK
BYTE
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
0
R6
R5
R4
R3
R2
R1
R0
(CONT)
Command or Data
ACK
BIT
1/0
1/0
______________________________________________________________________________________
43
MAX11800–MAX11803
4) I2C Readback Registers: 52h to 58h
• Direct conversion mode only (MAX11801/
MAX11803)
• Allows reading measurement results when in DCM
5) Panel Setup Commands: 6Ah to 6Fh
• Sets up panel prior to making X, Y, Z1, or Z2 measurements
6) Measurement Commands: 70h to 7Fh
• Performs specified measurement (X, Y, Z1, and/or
Z2)
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Table 18. Status and Configuration Registers
HEX
R6 R5 R4 R3 R2 R1 R0 ACCESS
PAIRABLE
AUTOINCREMENT
DATA
LENGTH
FUNCTION
00h
0
0
0
0
0
0
0
R
No
Yes
8
General status
01h
0
0
0
0
0
0
1
R/W
Yes
Yes
8
General configuration
02h
0
0
0
0
0
1
0
R/W
Yes
Yes
8
Measurement resolution
configuration
03h
0
0
0
0
0
1
1
R/W
Yes
Yes
8
Measurement averaging
configuration
04h
0
0
0
0
1
0
0
R/W
Yes
Yes
8
ADC sample time
configuration
05h
0
0
0
0
1
0
1
R/W
Yes
Yes
8
Panel setup times
configuration
06h
0
0
0
0
1
1
0
R/W
Yes
Yes
8
ADC delay initial conversion
configuration
07h
0
0
0
0
1
1
1
R/W
Yes
Yes
8
Touch-detect pullup times
configuration
08h
0
0
0
1
0
0
0
R/W
Yes
Yes
8
Autonomous mode timing
configuration (MAX11800/
MAX11801)
09h
0
0
0
1
0
0
1
R/W
Yes
Yes
8
Aperture settings (auto)
configuration (MAX11800/
MAX11801)
0Ah
0
0
0
1
0
1
0
R/W
Yes
Yes
8
Auxiliary measurement
configuration
0Bh
0
0
0
1
0
1
1
R/W
Yes
Yes
8
Operating mode
configuration
Data Readback Commands
Autonomous Conversion Mode
Use the readback command 0x50 to read back available
FIFO data in autonomous conversion modes (AUTO = 1)
(MAX11800/MAX11801). The oldest available data is
read out first. Data blocks vary from 32 to 64 bits in
length, depending on the scan mode selected. Reading
back longer than one block results in reading back the
next available block. The end-of-file indicator is read
back when no unread data is available in the FIFO. This
command does not autoincrement and the register
address does not advance beyond 0x50. See the FIFO
Data Block Readback Structure section for more details.
Direct Conversion Mode
Use the readback commands 0x52 to 0x5B to read
back available measurement data gathered in direct
44
conversion mode (AUTO = 0). Random data access is
supported within this register space and the commands
autoincrement up to register 0x5B. The register
address does not advance beyond register 0x5B.
Attempting to read back a pending conversion results
in data being tagged invalid. See the Direct Conversion
Mode Operations section for more details.
The panel setup and conversion commands are not
pairable in write mode as each command modifies the
panel setting both during and after the command,
based on conversion executions and CONT bit settings. All direct conversion commands modify the
expected I2C read register location to support the data
streamlining protocol. Table 21 shows the resulting
read register settings by command type applicable to
I2C variants.
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
HEX
R6
R5
R4
R3
R2
R1
R0
50h
1
0
1
0
0
0
X
DATA
LENGTH
ACCESS AUTOINCREMENT
Read
No
INF
OPERATION
Read next available FIFO
data block
Table 20. Data Readback Commands (Direct Mode Only)
AUTOINCREMENT
DATA
LENGTH
Read
Yes
8
X = MSB (direct conversion result)
1
Read
Yes
8
X = LSB (direct conversion result)
0
Read
Yes
8
Y = MSB (direct conversion result)
0
1
Read
Yes
8
Y = LSB (direct conversion result)
1
1
0
Read
Yes
8
Z1 = MSB (direct conversion result)
1
1
1
Read
Yes
8
Z1 = LSB (direct conversion result)
1
0
0
0
Read
Yes
8
Z2 = MSB (direct conversion result)
1
Read
Yes
8
Z2 = LSB (direct conversion result)
Read
Yes
8
AUX MSB (direct conversion result)
Read
No
8
AUX LSB (direct conversion result)
HEX
R6
R5
R4
R3
R2
R1
52h
1
0
1
0
0
1
0
53h
1
0
1
0
0
1
54h
1
0
1
0
1
0
55h
1
0
1
0
1
56h
1
0
1
0
57h
1
0
1
0
58h
1
0
1
59h
1
0
1
1
0
0
5Ah
1
0
1
1
0
1
5Bh
1
0
1
1
0
1
R0 ACCESS
0
1
OPERATION
Table 21. I2C Readback Register Settings Following Conversion Commands
COMMAND
READBACK REGISTER LOCATION
DESCRIPTION
X = panel setup
52h
X = MSB
Y = panel setup
Z1 = panel setup
54h
56h
Y = MSB
Z1 = MSB
Z2 = panel setup
58h
Z2 = MSB
X, Y = combined command
52h
X = MSB
X, Y, Z1 = combined command
52h
X = MSB
X, Y, Z1, Z2 = combined command
52h
X = MSB
AUX = conversion
5Ah
AUX = MSB
X = measurement
52h
X = MSB
Y = measurement
54h
Y = MSB
Z1 = measurement
56h
Z1 = MSB
Z2 = measurement
58h
Z2 = MSB
______________________________________________________________________________________
45
MAX11800–MAX11803
Table 19. FIFO Data Readback Command (Autonomous Mode Only––MAX11800/MAX11801)
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Panel Setup and
Measurement Commands
TSC conversion commands are only to be used in
direct conversion mode (AUTO = 0). Conversion commands issued during autonomous mode are ignored.
All panel setup and measurement operations are automated when in autonomous mode (AUTO = 1).
Commands must be issued in write mode to be executed. There are two types of commands: panel setup registers (0x6x) and measurement/conversion registers
(0x7x). All measurement commands indicate that the
ADC is used and the ADC can begin to power up once
the 0x7x header has been recognized. All measurement commands modify the target data register upon
the conclusion of the measurement command. The
CONT bit impacts the setup of the panel and ADC following the command. For panel setup commands and
combined commands, the user setting of this bit (R0) is
ignored. For these commands, the internal assumption
is shown in parentheses in Table 22.
The CONT bit impacts the setup of the panel and/or ADC
following the command (see command descriptions for
details). For some commands, the user setting of this bit
(R0) is ignored; for these commands the internal
assumption is shown in parentheses in Tables 8 and 22.
By definition, panel setup and measurement commands are NOT pairable in write mode as each command modifies the panel setting both during the
command and after it (based on conversion executions
and CONT bit settings).
Table 22. Measurement Commands
HEX
R6
R5
R4
R3
R2
R1
R0
ACCESS
PAIRABLE
COMMAND
LENGTH
7xh
1
1
1
0
0
0
(0)
Write
No
8
X, Y = combined measurement
7xh
1
1
1
0
0
1
(0)
Write
No
8
X, Y, Z1 = combined measurement
7xh
1
1
1
0
1
0
(0)
Write
No
8
X, Y, Z1, Z2 = combined measurement
7xh
1
1
1
0
1
1
(0)
Write
No
8
AUX = measurement
7xh
1
1
1
1
0
0
CONT
Write
No
8
X = measurement
7xh
1
1
1
1
0
1
CONT
Write
No
8
Y = measurement
7xh
1
1
1
1
1
0
CONT
Write
No
8
Z1 = measurement
7xh
1
1
1
1
1
1
CONT
Write
No
8
Z2 = measurement
46
OPERATION
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
General Status Register (0x00) (Read Only)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
NAME
ADC_BUSY
LPM
TDM
SCAN
FIFO_OVR
FIFO_INT
EDGE_INT
CONT_INT
DEFAULT
0
0
0
0
0
0
0
0
BIT
NAME
DESCRIPTION
7
ADC_BUSY
0: ADC is not in ACQ or CONV state
1: ADC is in ACQ or CONV state
This is for INTERNAL TEST only
6
LPM
0: Device is not in LPM or standby mode
1: Device is in LPM or standby mode
5
TDM
0: Device is not in TDM
1: Device is in TDM
4
SCAN
0: No scan or measurement in progress
1: Scan or measurement in progress
Also indicates presence of a continuous touch in autonomous mode
3
FIFO_OVR
0: FIFO overflow has not occurred (MAX11800/MAX11801)
1: FIFO has overflowed since last readback operation
Enabled only if AUTO = 1
2
FIFO_INT
0: No unread data in FIFO (MAX11800/MAX11801)
1: New data available in FIFO
Enabled only if AUTO = 1
1
EDGE_INT
0: No touch event in progress
1: Touch event in progress (cleared on ETAG = 10)
Enabled only if AUTO = 0 and EDGE_IRQ = 1
0
CONT_INT
0: No touch present
1: Touch present (or conversion in progress)
Enabled only if AUTO = 0 and EDGE_IRQ = 0
______________________________________________________________________________________
47
MAX11800–MAX11803
User Configuration Registers
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
General Configuration Register (0x01)
NAME
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
RT_SEL
HOLD_DO
PU_IRQ
ODN_IRQ
MASK_IRQ
EDGE_IRQ
1
1
1
1
0
0
DEFAULT
BIT
NAME
BIT 0
EDGE_TIME[1:0]
0
0
DESCRIPTION
7
RT_SEL
0: 50k touch-detection pullup resistance
1: 100k touch-detection pullup resistance
(panel setting––not to be confused with internal TIRQ pullup)
6
HOLD_DO
0: DOUT internal bus holder disabled
1: DOUT internal bus holder enabled
(applicable to SPI version only)
5
PU_IRQ
0: Disable IRQ internal pullup resistance
1: Enable IRQ internal pullup resistance
(open-drain mode only: ODN_IRQ also high)
4
ODN_IRQ
0: TIRQ is CMOS buffered output
1: TIRQ is open-drain nMOS output
3
MASK_IRQ
0: Enable TIRQ output
1: Mask/disable TIRQ output (force high or high impedance)
2
EDGE_IRQ
0: Use continuous interrupt with direct conversion mode
1: Use edge interrupt with direct conversion mode
EDGE_TIME[1:0]
TIRQ low time for edge interrupt mode only
00: 4 x (2MHz oscillator clock period) = 2μs
01: 16 x (2MHz oscillator clock period) = 8μs
10: 64 x (2MHz oscillator clock period) = 32μs
11: 128 x (2MHz oscillator clock period) = 128μs
1:0
BIT 1
Measurement Resolution Configuration Register (0x02)
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
NAME
—
—
—
PWR_SAV
RESX
RESY
RESZ1
RESZ2
DEFAULT
0
0
0
0
0
0
0
0
BIT
4
3:0
48
NAME
PWR_SAV
RES_
DESCRIPTION
0: Internal ADC runs at normal power
1: Internal ADC runs at reduced power and resolution
This mode does limit the effective ADC resolution:
12-bit conversions may be reduced to 10-bit accuracy
8-bit conversions should not be impacted.
Resolution for X, Y, Z1, or Z2 measurements
0: 12-bit conversion (see the PWR_SAV description in this table)
1: 8-bit conversion
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
BIT 7
DEFAULT
BIT 6
BIT 5
AVG_X[1:0]
NAME
0
BIT
BIT 4
0
0
AVG_X[1:0]
5:4
AVG_Y[1:0]
3:2
AVG_Z1[1:0]
1:0
AVG_Z2[1:0]
BIT 2
BIT 1
AVG_Z1[1:0]
0
NAME
7:6
BIT 3
AVG_Y[1:0]
0
BIT 0
AVG_Z2[1:0]
0
0
0
DESCRIPTION
Averaging sample depth for X, Y, Z1, or Z2 measurements
If AVG_FLT = 0 (see the Operating Mode Configuration Register (0x0B) section)
00: Single sample, no averaging
01: Take four samples, average two median samples
10: Take eight samples, average four median samples
11: Take 16 samples, average eight median samples
If AVG_FLT = 1 (see the Operating Mode Configuration Register (0x0B) section)
00: Single sample, no averaging
01: Take four samples, average all samples
10: Take eight samples, average all samples
11: Take 16 samples, average all samples
*The settings can be enabled and disabled through settings in the operating mode configuration register (0x0B), allowing for dynamic
configuration of averaging modes depending on operating mode.
ADC Sampling Time Configuration Register (0x04)*
BIT 7
NAME
DEFAULT
BIT
BIT 6
T_SAMPLE_X[1:0]
0
0
NAME
7:6
T_SAMPLE_X[1:0]
5:4
T_SAMPLE_Y[1:0]
3:2
T_SAMPLE_Z1[1:0]
1:0
T_SAMPLE_Z2[1:0]
BIT 5
BIT 4
T_SAMPLE_Y[1:0]
0
0
BIT 3
BIT 2
T_SAMPLE_Z1[1:0]
0
0
BIT 1
BIT 0
T_SAMPLE_Z2[1:0]
0
0
DESCRIPTION
Sampling time for X, Y, Z1 or Z2 measurements
00: 4 x (2MHz oscillator clock period) = 2μs
01: 16 x (2MHz oscillator clock period) = 8μs
10: 64 x (2MHz oscillator clock period) = 32μs
11: 256 x (2MHz oscillator clock period) = 128μs
*Time ADC spends sampling panel before starting conversion process. This time plus the ADC conversion time determines the sampling rate within averaging operations. Be sure to allow adequate time to settle the ADC capacitors given the panel effective source
resistance.
______________________________________________________________________________________
49
MAX11800–MAX11803
Measurement Averaging Configuration Register (0x03)*
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Panel Setup Timing Configuration Register (0x05)
BIT 7
BIT 6
0
0
BIT 4
BIT 3
BIT 2
0
0
0
PSUXY[3:0]
NAME
DEFAULT
BIT 5
BIT
NAME
7:4
PSUXY[3:0]
3:0
PSUZ[3:0]
BIT 1
BIT 0
PSUZ[3:0]
0
0
0
DESCRIPTION
X, Y panel setup times (position measurements)
0000: 0μs
1000: 1ms
0001: 20μs
1001: 2ms
0010: 50μs
1010: 5ms
0011: 80μs
1011: 10ms
0100: 100μs
1100: 20ms
0101: 200μs
1101: 50ms
0110: 500μs
1110: 100ms
0111: 800μs
1111: 200ms
Z panel setup times (pressure measurements)
PSUZ[3:0] has the same range as PSUXY[3:0] above.
Note: These settings apply to measurement commands, combined commands, and autonomous conversion mode measurements
and provide time for the panel to settle prior to beginning measurements. During these periods, the panel is set up, but the ADC
remains powered down. Users with low-impedance/fast settling panels should use setting 0000 (skip mode) if their panel can be settled during the required 10μs minimum delayed conversion time (see the Delayed Conversion Configuration Register (0x06) section).
Delayed Conversion Configuration Register (0x06)
BIT 7
BIT 6
0
0
BIT
BIT 4
BIT 3
BIT 2
0
0
0
D_CV_XY[3:0]
NAME
DEFAULT
BIT 5
NAME
7:4
D_CV_XY[3:0]
3:0
D_CV_Z[3:0]
0
BIT 1
BIT 0
D_CV_Z[3:0]
0
0
DESCRIPTION
X, Y panel plus ADC setup times (position measurements)
0000: 10μs
1000: 1ms
0001: 20μs
1001: 2ms
0010: 50μs
1010: 5ms
0011: 80μs
1011: 10ms
0100: 100μs
1100: 20ms
0101: 200μs
1101: 50ms
0110: 500μs
1110: 100ms
0111: 800μs
1111: 200ms
Z panel plus ADC setup times (pressure measurements)
D_CV_Z[3:0] has the same range as D_CV_XY[3:0] above.
Note: These settings apply to measurement commands, combined commands, and autonomous conversion mode measurements
and provide time for the panel and ADC to settle prior to beginning measurements. During these periods, the panel is set up and the
ADC is powered up. In general, users with long panel settling requirements should minimize time in this mode, using increased
panel setup times instead to save ADC power.
50
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
MAX11800–MAX11803
Touch-Detect Pullup Timing Configuration Register (0x07)
BIT 7
BIT 6
DEFAULT
BIT 5
BIT 4
BIT 3
BIT 2
PUR[3:0]
NAME
0
BIT
0
0
0
0
NAME
7:4
PUR[3:0]
3:0
PUF[3:0]
BIT 1
BIT 0
0
0
PUF[3:0]
0
DESCRIPTION
Rough pullup time (tPUR)
0000: 2μs*
1000: 1ms
0001: 2μs
1001: 2ms
0010: 4μs
1010: 5ms
0011: 8μs
1011: 10ms
0100: 10μs
1100: 20ms
0101: 50μs
1101: 50ms
0110: 100μs
1110: 100ms
0111: 500μs
1111: 200ms
Fine pullup time (tPUF)
0000: 10μs
1000: 1ms
0001: 20μs
1001: 2ms
0010: 50μs
1010: 5ms
0011: 80μs
1011: 10ms
0100: 100μs
1100: 20ms
0101: 200μs
1101: 50ms
0110: 500μs
1110: 100ms
0111: 800μs
1111: 200ms
Note: These settings apply to the end of all measurement and combined commands and are required for proper data tagging and
interrupt management. The exception is direct conversion commands with CONT = 1. These commands do not enter PUR/PUF intervals for the purpose of data tagging.
*While 2μs is the minimum PUR interval listed, for this setting, the XPSW is not engaged, allowing for minimal power operation
(essentially adding 2μs to the PUF time).
Autonomous Mode Timing Configuration Register (0x08) (MAX11800/MAX11801)
BIT 7
BIT 6
0
0
BIT 4
BIT 3
BIT 2
0
0
0
TINIT[3:0]
NAME
DEFAULT
BIT 5
BIT
NAME
7:4
TINIT[3:0]
3:0
SCANP[3:0]
BIT 1
BIT 0
SCANP[3:0]
0
0
0
DESCRIPTION
Initial period (time between touch and initial scan block, tINIT)
0000: 10μs
1000: 1ms
0001: 20μs
1001: 2ms
0010: 50μs
1010: 5ms
0011: 80μs
1011: 10ms
0100: 100μs
1100: 20ms
0101: 200μs
1101: 50ms
0110: 500μs
1110: 100ms
0111: 800μs
1111: 200ms
Scan period (time between successive scan blocks, tSP)
SCANP[3:0] has the same range as TINIT[3:0] above.
Note: These settings apply in autonomous conversion mode only.
______________________________________________________________________________________
51
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Aperture Configuration Register (0x09) (MAX11800/MAX11801)
BIT 7
BIT 6
0
0
BIT 4
BIT 3
BIT 2
0
0
0
APRX[3:0]
NAME
DEFAULT
BIT 5
BIT
BIT 0
APRY[3:0]
0
NAME
BIT 1
0
0
DESCRIPTION
±ΔX for aperture checking
0000 = 2-1 LSB = aperture checking disabled
0001 = 2(1-1) LSB = ±1 LSB
0010 = 2(2-1) LSB = ±2 LSB
0011 = 2(3-1) LSB = ±4 LSB
7:4
APRX[3:0]
.
.
.
1001 = 2(9-1) LSB = ±256 LSB
1010 = 2(10-1) LSB = ±512 LSB
1011 = 2(11-1) LSB = ±1024 LSB
1100 = 2(12-1) LSB = ±2048 LSB
1101 to 1111 = aperture checking disabled
3:0
APRY[3:0]
±ΔY for aperture checking
APRY[3:0] has the same range as APRX[3:0] above.
Note: These aperture settings apply in autonomous conversion mode only and control whether data meets the criteria for logging
into the FIFO.
52
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
MAX11800–MAX11803
Auxiliary Measurement Configuration Register (0x0A)
BIT 7
BIT 6
D_CV_A[3:0]
NAME
0
DEFAULT
BIT
7:5
4:3
2:1
0
BIT 5
0
BIT 4
BIT 3
BIT 2
T_SAMPLE_A[1:0]
0
0
NAME
0
BIT 1
AVGA[1:0]
0
BIT 0
RESA
0
0
DESCRIPTION
D_CV_A[3:0]
Delay initial auxiliary conversion
000: 10μs
001: 100μs
010: 500μs
011: 1ms
100: 5ms
101: 10ms
110: 50ms
111: 100ms
T_SAMPLE_A[1:0]
Sampling time for auxiliary measurements
00: 4 x (2MHz oscillator clock period) = 2μs
01: 16 x (2MHz oscillator clock period) = 8μs
10: 64 x (2MHz oscillator clock period) = 32μs
11: 256 x (2MHz oscillator clock period) = 128μs
AVGA[1:0]
Averaging sample depth for auxiliary measurements
If AVG_FLT = 0 (see the Operating Mode Configuration Register (0x0B) section)
00: Single sample, no averaging
01: Take four samples, average two median samples
10: Take eight samples, average four median samples
11: Take 16 samples, average eight median samples
If AVG_FLT = 1 (see the Operating Mode Configuration Register (0x0B) section)
00: Single sample, no averaging
01: Take four samples, average all samples
10: Take eight samples, average all samples
11: Take 16 samples, average all samples
RESA
Resolution for auxiliary measurements
0: 12-bit conversion (see the description of PWR_SAV in the Measurement Resolution
Configuration Register (0x02) section)
1: 8-bit conversion
Note: A delimiter refers to the auxiliary input (AUX). Auxiliary measurements can only be requested in direct conversion modes.
______________________________________________________________________________________
53
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Operating Mode Configuration Register (0x0B)
BIT 7
NAME
BIT 6
PWRDN
AMODE[1:0]
1
DEFAULT
BIT
BIT 5
0
0
NAME
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
APER
AVG_FLT
EN_AVG_XY
EN_AVG_Z
0
0
0
0
0
DESCRIPTION
PWRDN
0: Device is powered up and operational in either a direct or autonomous conversion
mode (see AMODE[1:0] below).
1: Device is powered down, OTP is held in reset
AMODE[1:0]
00: Direct conversion mode (AUTO = 0) (MAX11800/MAX11801)
01: Autonomous X and Y scan (AUTO = 1)
10: Autonomous X, Y, Z1 scan (AUTO = 1)
11: Autonomous X, Y, Z1, Z2 scan (AUTO = 1)
4
APER
0: Disregard aperture criteria (MAX11800/MAX11801)
1: Enable aperture criteria (spatial filter)
(applies to autonomous modes only)
3
AVG_FLT
0: Use median averaging filters (ignore outliers)
1: Use straight averaging filters
2
EN_AVG_XY
0: Disable (X, Y) position averaging in selected mode
1: Enable (X, Y) position averaging in selected mode
1
EN_AVG_Z
0: Disable (Z1, Z2) pressure averaging in selected mode
1: Enable (Z1, Z2) pressure averaging in selected mode
0
RESERVED
Reserved bit.
7
6:5
*Any write access to 0x0B initiates an internal reset pulse. This pulse clears the FIFO and all measurement memories.
54
______________________________________________________________________________________
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
VDD
1μF
0.1μF
VDD
X+
TIRQ
GPIO
DIN
DOUT
Y+
MAX11800
MAX11802
HOST
PROCESSOR
CLK
CLK
DOUT
DIN
CS
CS
X-
TOUCH SCREEN
YAUX
AUX INPUT
GND
MAX11801/MAX11803 Typical Operating Circuit
VDD
1μF
0.1μF
1.2kΩ
X+
1.2kΩ
OPTIONAL
VDD
TIRQ
GPIO
SDA
SDA
Y+
MAX11801
MAX11803
HOST
PROCESSOR
SCL
SCL
XA0
A0
A1
A1
TOUCH SCREEN
YAUX INPUT
AUX
GND
______________________________________________________________________________________
55
MAX11800–MAX11803
MAX11800/MAX11802 Typical Operating Circuit
MAX11800–MAX11803
Low-Power, Ultra-Small Resistive Touch-Screen
Controllers with I2C/SPI Interface
Pin Configurations
TOP VIEW
CS
CLK
DIN
9
8
7
MAX11800/MAX11802
1
2
3
4
X-
Y-
TIRQ
DIN
VDD
GND
DOUT
CLK
X+
Y+
AUX
CS
+
A
DOUT 10
AUX 11
Y+ 12
MAX11800
MAX11802
*EP
+
1
2
3
X+
VDD
GND
6
TIRQ
5
Y-
4
X-
B
C
WLP
TQFN
A0
SCL
9
8
MAX11801/MAX11803
SDA
7
1
2
3
4
X-
Y-
TIRQ
SDA
VDD
GND
A1
SCL
X+
Y+
AUX
A0
+
A
6
A1 10
AUX 11
Y+ 12
5
MAX11801
MAX11803
*EP
+
1
2
3
X+
VDD
GND
4
TIRQ
Y-
X-
B
C
WLP
TQFN
*EXPOSED PAD.
Package Information
Chip Information
PROCESS: CMOS
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
12 TQFN
T1244+4
21-0139
12 WLP
W121A2-1
21-0009
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
56 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2009 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.