Maxim MAX1233ETI ±15kv esd-protected touch-screen controllers include dac and keypad controller Datasheet

19-2512; Rev 4; 3/08
KIT
ATION
EVALU
E
L
B
AVAILA
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
The MAX1233/MAX1234 are complete PDA controllers in
5mm × 5mm, 28-pin QFN and TQFN packages. They feature a 12-bit analog-to-digital converter (ADC), low onresistance switches for driving resistive touch screens, an
internal +1.0V/+2.5V or external reference, ±2°C accurate, on-chip temperature sensor, direct +6V battery monitor, keypad controller, 8-bit digital-to-analog converter
(DAC), and a synchronous serial interface. Each of the
keypad controllers’ eight row and column inputs can be
reconfigured as general-purpose parallel I/O pins (GPIO).
All analog inputs are fully ESD protected, eliminating the
need for external TransZorb™ devices.
The MAX1233/MAX1234 offer programmable resolution
and sampling rates. Interrupts from the devices alert the
host processor when data is ready, when the screen is
touched, or a key press is detected. Softwareconfigurable scan control and internal timers give the user
flexibility without burdening the host processor. These
devices consume only 260µA at the maximum sampling
rate of 50ksps. Supply current falls to below 50µA for
sampling rates of 10ksps. The MAX1233/MAX1234 are
guaranteed over the -40°C to +85°C temperature range.
Applications
Personal Digital Assistants
♦ ESD-Protected Analog Inputs
±15kV IEC 1000-4-2 Air-Gap Discharge
±8kV IEC 1000-4-2 Contact Discharge
♦ Single-Supply Operation
+2.7V to +3.6V (MAX1233)
+4.75V to +5.25V (MAX1234)
♦ 4-Wire Touch-Screen Interface
♦ Internal +1.0V/+2.5V Reference or External
Reference (+1.0V to AVDD)
♦ SPI™/QSPI™/MICROWIRE™-Compatible 10MHz
Serial Interface
♦ 12-Bit, 50ksps ADC Measures
Resistive Touch-Screen Position and Pressure
Two Auxiliary Analog Inputs
Two Battery Voltages (0.5V to 6V)
On-Chip Temperature
♦ 8-Bit DAC for LCD Bias Control
♦ 4 × 4 Keypad Programmable Controller Offers Up
to Eight GPIO Pins
♦ Automatic Detection of Screen Touch, Key Press,
and End of Conversion
♦ Programmable 8-, 10-, 12-Bit Resolution
Pagers
♦ Programmable Conversion Rates
Touch-Screen Monitors
♦ AutoShutdown™ Between Conversions
Cellular Phones
♦ Low Power
260µA at 50ksps
50µA at 10ksps
6µA at 1ksps
0.3µA Shutdown Current
MP3 Players
Portable Instruments
Point-of-Sale Terminals
CS
SCLK
DIN
BUSY
DOUT
PENIRQ
KEYIRQ
28
27
26
25
24
23
22
Pin Configuration
TOP VIEW
Features
♦ 28-Pin 5mm × 5mm QFN and TQFN Packages
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
DVDD
1
21
C4
AVDD
2
20
C3
*X+
3
19
C2
MAX1233ETI
-40°C to +85°C
28 TQFN (5mm x 5mm)
*Y+
4
18
C1
MAX1234EGI
-40°C to +85°C
28 QFN (5mm x 5mm)
*X-
5
17
R1
*Y-
6
16
R2
MAX1234ETI
-40°C to +85°C
28 TQFN (5mm x 5mm)
GND
7
15
R3
10
11
12
13
14
*AUX2
REF
DACOUT
R4
9
*BAT2
*AUX1
8
*BAT1
MAX1233
MAX1234
QFN/TQFN
*PIN INCLUDES 8kV/15kV ESD PROTECTION.
MAX1233EGI
-40°C to +85°C
28 QFN (5mm x 5mm)
TransZorb is a trademark of General Semiconductor Industries, Inc.
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
AutoShutdown is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ 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
MAX1233/MAX1234
General Description
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ABSOLUTE MAXIMUM RATINGS
AVDD to GND............................................................-0.3V to +6V
DVDD to AVDD .......................................................-0.3V to +0.3V
Digital Inputs/Outputs to GND .................-0.3V to (DVDD + 0.3V)
X+, Y+, X-, Y-, AUX1, AUX2,
and REF to GND ..................................-0.3V to (AVDD + 0.3V)
BAT1, BAT2 to GND .................................................-0.3V to +6V
Maximum ESD per IEC 1000-4-2 (per MIL STD-883 HBM)
X+, X-, Y+, Y-, AUX1, AUX2, BAT1, BAT2......................±15kV
All Other Pins.....................................................................±2.5kV
Maximum Current into Any Pin............................................50mA
Continuous Power Dissipation (TA = +70°C)
28-Pin QFN (derate 28.5mW/°C above +70°C) .................2W
28-Pin TQFN (derate 28.5mW/°C above +70°C) ...............2W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-60°C to +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
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V
(MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA = -40°C to
+85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
12
Bits
ANALOG-TO-DIGITAL CONVERTER
DC ACCURACY (Note 1)
Resolution
Software-programmable 8/10/12 bit
No Missing Codes
11
Relative Accuracy (Note 2)
INL
Differential Nonlinearity
DNL
Offset Error
Gain Error (Note 3)
Total Unadjusted Error
TUE
Bits
12-bit mode
±0.8
10-bit and 8-bit modes
±0.5
12-bit mode
±0.8
10-bit and 8-bit modes
±0.5
12-bit mode
±0.5
10-bit and 8-bit modes
±0.5
12-bit mode
±0.5
10-bit mode
±0.5
8-bit mode
±0.5
12-bit mode
±2
10-bit and 8-bit modes
±1
±2
±2
±4
LSB
LSB
LSB
±4
LSB
LSB
Offset Temperature Coefficient
±0.4
ppm/°C
Gain Temperature Coefficient
±0.4
ppm/°C
Channel-to-Channel Offset
±0.1
LSB
Channel-to-Channel Gain
Matching
±0.1
LSB
50
µVRMS
Noise
Power-Supply Rejection
Including internal VREF
PSR
Full-scale
input
MAX1233
AVDD = DVDD = +2.7V to +3.6V
±0.4
MAX1234
AVDD = DVDD = +5V ±5%
±0.3
mV
DYNAMIC SPECIFICATIONS (1kHz SINE WAVE, VIN = 2.5VP-P FOR MAX1233, VIN = 4.096VP-P FOR MAX1234, 50ksps,
fSCLK = 10MHz)
Signal-to-Noise Plus Distortion
2
SINAD
69
_______________________________________________________________________________________
dB
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V
(MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA = -40°C to
+85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
Total Harmonic Distortion
THD
Spurious-Free Dynamic Range
SFDR
CONDITIONS
MIN
TYP
MAX
-84
UNITS
dB
84
dB
Full-Power Bandwidth
-3dB point
0.5
MHz
Full-Linear Bandwidth
SINAD > 67dB
50
kHz
CONVERSION RATE
Internal Oscillator Frequency
8
11.5
MHz
Aperture Delay
30
ns
Aperture Jitter
<50
ps
Maximum Serial Clock Frequency
fSCLK
10
Duty Cycle
MHz
30
70
%
0
VREF
V
±1
µA
AUXILIARY ANALOG INPUTS (AUX1, AUX2)
Input Voltage Range
Channel not selected or conversion
stopped
Input Leakage Current
±0.1
Input Capacitance
34
pF
BATTERY MONITOR INPUTS (BAT1, BAT2)
Input Voltage Range
0.5
6.0
Sampling battery
Input Impedance
10
Battery monitor OFF
Accuracy
Internal reference
1
-3
V
kΩ
GΩ
+3
%
+85
°C
TEMPERATURE MEASUREMENT
Temperature Range
-40
Resolution
Accuracy
Differential method (Note 4)
1.6
Single measurement method (Note 5)
0.3
Differential method (Note 4)
±3
Single measurement method (Note 5)
±2
°C
°C
INTERNAL ADC REFERENCE
Reference Output Voltage
Output Tempco
VREF
2.5V mode, TA = +25°C
2.470
2.500
2.530
1.0V mode, TA = +25°C
0.980
1.000
1.020
TCVREF
Reference Output Impedance
60
Normal operation
Reference Short-Circuit Current
V
ppm/°C
250
Ω
18
mA
EXTERNAL ADC REFERENCE (INTERNAL REFERENCE DISABLED, REFERENCE APPLIED TO REF)
Reference Input Voltage Range
(Note 6)
Input Impedance
CS = GND or VDD
1
VREF = +2.5V at 50ksps (MAX1233)
5
10
VREF = +4.096V at 50ksps (MAX1234)
8
15
Input Current
Shutdown/between conversions
1.0
VDD
V
GΩ
µA
±0.1
_______________________________________________________________________________________
3
MAX1233/MAX1234
ELECTRICAL CHARACTERISTICS (continued)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V
(MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA = -40°C to
+85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL-TO-ANALOG CONVERTER
DC ACCURACY
Resolution
8
Bits
Integral Linearity Error
INL
(Note 7)
±1.0
LSB
Differential Linearity Error
DNL
No missing codes
±1.0
LSB
Offset Error
VOS
(Note 8)
±25
mV
±1
Offset Error Temperature
Coefficient
1
ppm/°C
Full-Scale Error
Code = 255, no load
5
%
Full-Scale Error Temperature
Coefficient
Code = 255, no load
±10
ppm/°C
Positive and negative
0.4
V/µs
DYNAMIC PERFORMANCE
Voltage Output Slew Rate
Output Settling Time
0.5LSB; 50kΩ and 50pF load (Note 9)
20
µs
Glitch Impulse
Code 127 to 128
40
nV/s
Wake-Up Time
From shutdown
50
µs
DAC OUTPUT
Internal DAC Reference
VREFDAC
Output Load Regulation
Output Resistance
(Note 10)
0.85 ✕
AVDD
0.9 ✕
AVDD
Code = 255; 0 to 100µA
0.5
Code = 0; 0 to 100µA
0.5
Power-down mode
1.0
0.95 ✕
AVDD
V
LSB
MΩ
TOUCH-SCREEN CONTROLLER
On-Resistance
Touch-Detection Internal Pullup
Resistance
Y+, X+
7
Y-, X-
9
X+ to AVDD
1
MΩ
Ω
KEYPAD CONTROLLER
Pullup Resistance
C4, C3, C2, C1 (Note 11)
0.5
kΩ
Pulldown Resistance
R4, R3, R2, R1 (Note 11)
16
kΩ
DIGITAL INTERFACE
DIGITAL INPUTS (SCLK, CS, DIN, R_, C_)
Input Voltage Low
VIL
Input Voltage High
VIH
Input Leakage Current
4
IL
0.3 ✕
DVDD
0.7 ✕
DVDD
V
V
±0.1
_______________________________________________________________________________________
±1
µA
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V
(MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA = -40°C to
+85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
Input Capacitance
SYMBOL
CONDITIONS
MIN
CIN
TYP
MAX
15
UNITS
pF
DIGITAL OUTPUT (DOUT)
Output Voltage Low
VOL
Output Voltage High
VOH
ISINK = 2mA
0.4
ISINK = 4mA
0.8
ISOURCE = 1.5mA
DVDD 0.5
V
V
DIGITAL OUTPUT (BUSY, PENIRQ, KEYIRQ, R_, C_)
Output Voltage Low
VOL
ISINK = 0.2mA
Output Voltage High
VOH
ISOURCE = 0.2mA
0.4
DVDD 0.5
V
V
POWER REQUIREMENTS
Supply Voltage (Note 12)
Analog and Digital Supply
Current
AVDD /
DVDD
IAVDD +
IDVDD
MAX1233
2.7
3
3.6
MAX1234
4.75
5
5.25
Idle; all blocks shut down
0.5
5
Only ADC on; fSAMPLE = 20ksps
150
500
Only DAC on; no load
150
230
Only internal reference on
670
900
V
µA
TIMING CHARACTERISTICS
SCLK Clock Period
tCP
100
ns
SCLK Pulse Width High
tCH
40
ns
SCLK Pulse Width Low
tCL
40
ns
DIN to SCLK Rise Setup
tDS
40
ns
SCLK Rise to DIN Hold
tDH
0
ns
SCLK Fall to DOUT Valid
tDOV
CLOAD = 50pF
40
ns
CS Fall to DOUT Enabled
tDV
CLOAD = 50pF
45
ns
CS Rise to DOUT Disabled
tDOD
CLOAD = 50pF
40
ns
CS Fall to SCLK Rise
tCSS
CS Fall to SCLK Ignored
tCSH
SCLK Rise to R_/C_ Data Valid
tGPO
CS Pulse Width High
tCSW
40
ns
0
CLOAD = 50pF (Note 13)
ns
230
40
ns
ns
Note 1: Tested at DVDD = AVDD = +2.7V (MAX1233), DVDD = AVDD = +5V (MAX1234).
Note 2: Relative accuracy is the deviation of the analog value at any code from its theoretical value after the offset and gain errors
have been removed.
Note 3: Offset nulled.
Note 4: Difference between TEMP1 and TEMP2; temperature in °K = (VTEMP2 - VTEMP1) × 2680°K/V. No calibration is necessary.
Note 5: Temperature coefficient is -2.1mV/°C. Determine absolute temperature by extrapolating from a calibrated value.
Note 6: ADC performance is limited by the conversion noise floor, typically 300µVP-P. An external reference below 2.5V can
compromise the ADC performance.
Note 7: Guaranteed from code 5 to 255.
_______________________________________________________________________________________
5
MAX1233/MAX1234
ELECTRICAL CHARACTERISTICS (continued)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ELECTRICAL CHARACTERISTICS (continued)
(DVDD = AVDD = +2.7V to +3.6V (MAX1233), DVDD = AVDD = +4.75V to +5.25V (MAX1234), external reference VREF = 2.5V
(MAX1233), VREF = 4.096V (MAX1234); fSCLK = 10MHz, fSAMPLE = 50ksps, 12-bit mode, 0.1µF capacitor at REF, TA = -40°C to
+85°C, unless otherwise noted. Typical values are at TA = +25°C.)
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
The offset value extrapolated from the range over which the INL is guaranteed.
Output settling time is measured by stepping from code 5 to 255, and from code 255 to 5.
Actual output voltage at full scale is 255/256 × VREFDAC.
Resistance is open when configured as GPIO or in shutdown.
AVDD and DVDD should not differ by more than 300mV.
When configured as GPIO.
Timing Diagram
CS
tCSW
tCH
tCSS
tCP
tCSH
tCL
tCSH
tCSS
SCLK
tDH
tDS
DIN
tDOV
tDOD
tDV
DOUT
R_/C_
NOTE: TIMING NOT TO SCALE.
6
tGPO
_______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
SHUTDOWN CURRENT
vs. TEMPERATURE
200
150
100
50
200
150
100
50
2.7
3.2
3.7
4.2
4.7
9.8
9.6
9.4
9.2
9.0
8.8
8.6
8.4
MAX1233/MAX1234
8.2
8.0
-40
5.2
MAX1233/34 toc03
10.0
0
0
-20
0
20
40
60
2.7
80
3.2
3.7
4.2
4.7
AVDD (V)
TEMPERATURE (°C)
AVDD (V)
INTERNAL OSCILLATOR FREQUENCY
vs. TEMPERATURE
TEMP1 DIODE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
TEMP1 DIODE VOLTAGE
vs. TEMPERATURE
MAX1234, AVDD = +5.0V
9.4
9.2
9.0
0.64
0.62
0.60
0.58
0.56
0.50
20
40
60
0.60
0.55
0.50
0.40
2.7
80
0.65
3.2
TEMPERATURE (°C)
3.7
4.2
4.7
5.2
-40 -25 -10
5
AVDD (V)
20
35
50
65
80
TEMPERATURE (°C)
TEMP2 DIODE VOLTAGE
vs. TEMPERATURE
TEMP2 DIODE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
0.75
0.70
0.65
0.90
0.85
TEMP2 DIODE VOLTAGE (V)
0.80
MAX1233/34 toc08
0
MAX1233/34 toc07
-20
TEMP2 DIODE VOLTAGE (V)
-40
0.70
0.45
0.52
8.6
MAX1233/34 toc06
0.75
0.54
MAX1233, AVDD = +3.0V
8.8
0.66
5.2
0.80
TEMP1 DIODE VOLTAGE (V)
0.68
TEMP1 DIODE VOLTAGE (V)
9.6
MAX1233/34 toc05
0.70
MAX1233/34 toc04
9.8
INTERNAL OSCILLATOR FREQUENCY (MHz)
MAX1233/34 toc02
250
SHUTDOWN CURRENT (nA)
250
SHUTDOWN CURRENT (nA)
300
MAX1233/34 toc01
300
INTERNAL OSCILLATOR FREQUENCY
vs. ANALOG SUPPLY VOLTAGE
INTERNAL OSCILLATOR FREQUENCY (MHz)
SHUTDOWN CURRENT
vs. ANALOG SUPPLY VOLTAGE
0.80
0.75
0.70
0.65
0.60
0.60
2.7
3.2
3.7
4.2
AVDD (V)
4.7
5.2
-40 -25 -10
5
20
35
50
65
80
TEMPERATURE (°C)
_______________________________________________________________________________________
7
MAX1233/MAX1234
Typical Operating Characteristics
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK =
10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1µF capacitor at REF, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK =
10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1µF capacitor at REF, TA = +25°C, unless otherwise noted.)
ADC DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
ADC INTEGRAL NONLINEARITY
vs. OUTPUT CODE
0.6
0.8
0.6
0.4
0.2
0.2
DNL (LSB)
0.4
0
-0.2
MAX1233/34 toc10
0.8
INL (LSB)
1.0
MAX1233/34 toc09
1.0
0
-0.2
-0.4
-0.4
-0.6
-0.6
-0.8
-0.8
-1.0
-1.0
0
0
500 1000 1500 2000 2500 3000 3500 4000
500 1000 1500 2000 2500 3000 3500 4000
OUTPUT CODE
OUTPUT CODE
ADC OFFSET ERROR
vs. ANALOG SUPPLY VOLTAGE
ADC OFFSET ERROR vs. TEMPERATURE
1.5
OFFSET ERROR (LSB)
1.0
0.5
0
-0.5
1.0
0.5
0
-0.5
-1.0
-1.0
-1.5
-1.5
-2.0
-2.0
3.2
3.7
4.2
4.7
-40
5.2
-20
0
20
40
AVDD (V)
TEMPERATURE (°C)
ADC GAIN ERROR
vs. ANALOG SUPPLY VOLTAGE
ADC GAIN ERROR
vs. TEMPERATURE
1.5
0.5
0
-0.5
80
1.0
0.5
0
-0.5
-1.0
-1.0
-1.5
-1.5
-2.0
60
1.5
GAIN ERROR (LSB)
1.0
80
2.0
MAX1233/34 toc13
2.0
60
MAX1233/34 toc14
2.7
-2.0
2.7
3.2
3.7
4.2
AVDD (V)
8
MAX1233/34 toc12
1.5
OFFSET ERROR (LSB)
2.0
MAX1233/34 toc11
2.0
GAIN ERROR (LSB)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
4.7
5.2
-40
-20
0
20
40
TEMPERATURE (°C)
_______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ADC EXTERNAL REFERENCE INPUT
CURRENT vs. SAMPLING RATE
ADC SUPPLY CURRENT
vs. SAMPLING RATE
SUPPLY CURRENT (μA)
6
4
2
100
10
1
0
0.1
1k
100k
10k
1
10
100
1k
10k
fSAMPLE (Hz)
fSAMPLE (Hz)
ADC SUPPLY CURRENT
vs. SUPPLY VOLTAGE
ADC SUPPLY CURRENT
vs. TEMPERATURE
EXTERNAL REF
fSAMPLE = 20ksps
200
150
100
140
AVDD = +3V
120
SUPPLY CURRENT (μA)
MAX1233/34 toc17
250
100k
MAX1233/34 toc18
100
SUPPLY CURRENT (μA)
MAX1233/34 toc16
MAX1233
VREF = +2.5V
REFERENCE CURRENT (μA)
1000
MAX1233/34 toc15
8
100
80
60
40
50
20
0
0
2.7
3.2
3.7
4.2
4.7
-40
5.2
0
20
40
60
80
TEMPERATURE (°C)
DAC INTEGRAL NONLINEARITY vs. CODE
DAC DIFFERENTIAL NONLINEARITY
vs. OUTPUT CODE
0.050
MAX1233/34 toc20
0.075
MAX1233/34 toc19
0.075
0.050
0.025
0.025
DNL (LSB)
INL (LSB)
-20
AVDD (V)
0
-0.025
-0.050
0
-0.025
-0.500
-0.075
-0.075
-0.100
-0.100
0
50
100
150
CODE
200
250
300
0
50
100
150
200
250
300
OUTPUT CODE
_______________________________________________________________________________________
9
MAX1233/MAX1234
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK =
10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1µF capacitor at REF, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK =
10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1µF capacitor at REF, TA = +25°C, unless otherwise noted.)
DAC FULL-SCALE ERROR
vs. TEMPERATURE
MAX1233/34 toc21
0.8
0.50
0.8
0.25
0.4
0.25
0.4
0
0
-0.4
-0.8
-0.50
-0.8
-1.2
5.5
-0.75
-0.4
-0.50
3.0
3.5
4.0
4.5
5.0
0
0
-0.25
-0.25
-1.2
-40
-20
0
20
40
60
AVDD (V)
TEMPERATURE (°C)
DAC SUPPLY CURRENT
vs. ANALOG SUPPLY VOLTAGE
DAC SUPPLY CURRENT
vs. TEMPERATURE
200
MAX1233/34 toc23
250
175
DAC SUPPLY CURRENT (μA)
200
80
MAX1233/34 toc24
2.5
FULL-SCALE ERROR (LSB)
0.50
FULL-SCALE ERROR (%)
FULL-SCALE ERROR (LSB)
1.2
0.75
-0.75
DAC SUPPLY CURRENT (μA)
MAX1233/34 toc22
1.2
0.75
150
100
50
FULL-SCALE ERROR (%)
DAC FULL-SCALE ERROR
vs. ANALOG SUPPLY VOLTAGE
150
125
100
75
50
25
0
0
3.7
4.2
4.7
5.2
-40
-20
0
20
ADC REFERENCE VOLTAGE
vs. ANALOG SUPPLY VOLTAGE
ADC REFERENCE VOLTAGE
vs. TEMPERATURE
MAX1233/34 toc25
2.525
1.020
2.60
1.010
2.55
1.000
2.500
VREF (V)
VREF = 1.0V
MAX1233/34 toc26
2.450
3.7
4.2
AVDD (V)
1.250
1.125
2.50
1.000
VREF = 2.5V
3.2
80
VREF = 1.0V
2.475
10
60
TEMPERATURE (°C)
2.550
2.7
40
AVDD (V)
4.7
5.2
0.990
2.45
0.980
2.40
-40
VREF = 2.5V
0.875
0.750
-20
0
20
40
60
80
TEMPERATURE (°C)
______________________________________________________________________________________
VREF (V)
3.2
VREF (V)
2.7
VREF (V)
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
ADC REFERENCE SUPPLY CURRENT
vs. ANALOG SUPPLY VOLTAGE
SUPPLY CURRENT (μA)
700
650
600
MAX1233/34 toc28
750
MAX1233/34 toc27
SUPPLY CURRENT (μA)
750
REFERENCE SUPPLY CURRENT
vs. TEMPERATURE
700
650
600
550
550
2.7
3.2
3.7
4.2
4.7
5.2
-40 -25 -10
AVDD (V)
5
20 35 50
TEMPERATURE (°C)
65
80
Pin Description
PIN
NAME
FUNCTION
1
DVDD
Positive Digital Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234. Bypass
with a 0.1µF capacitor. Must be within 300mV of AVDD.
2
AVDD
Positive Analog Supply Voltage, +2.7V to +3.6V for MAX1233, +4.75V to +5.25V for MAX1234.
Bypass with a 0.1µF capacitor. Must be within 300mV of DVDD.
3*
X+
X+ Position Input
4*
Y+
Y+ Position Input
5*
X-
X- Position Input
6*
Y-
Y- Position Input
7
GND
Analog and Digital Ground
8*
BAT1
Battery Monitoring Input 1. Measures battery voltages up to 6V.
9*
BAT2
Battery Monitoring Input 2. Measures battery voltages up to 6V.
10*
AUX1
Auxiliary Analog Input 1 to ADC. Measures analog voltages from zero to VREF.
11*
AUX2
Auxiliary Analog Input 2 to ADC. Measures analog voltages from zero to VREF.
Voltage Reference Output/Input. Reference voltage for analog-to-digital conversion. In internal
reference mode, the reference buffer provides a 2.5V or 1.0V nominal output. In external reference
mode, apply a reference voltage between 1.0V and AVDD. Bypass REF to GND with a 0.1µF
capacitor in the external reference mode only.
12
REF
13
DACOUT
14
R4
Keypad Row 4. Can be reconfigured as GPIO3.
15
R3
Keypad Row 3. Can be reconfigured as GPIO2.
16
R2
Keypad Row 2. Can be reconfigured as GPIO1.
17
R1
Keypad Row 1. Can be reconfigured as GPIO0.
18
C1
Keypad Column 1. Can be reconfigured as GPIO4.
DAC Voltage Output; 0.9 × AVDD Full Scale
______________________________________________________________________________________
11
MAX1233/MAX1234
Typical Operating Characteristics (continued)
(AVDD = DVDD = 3V (MAX1233) or 5V (MAX1234), external VREF = +2.5V (MAX1233), external VREF = +4.096V (MAX1234), fSCLK =
10MHz (50% duty cycle), fSAMPLE = 20ksps, CLOAD = 50pF, 0.1µF capacitor at REF, TA = +25°C, unless otherwise noted.)
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
Pin Description (continued)
PIN
NAME
19
C2
Keypad Column 2. Can be reconfigured as GPIO5.
FUNCTION
20
C3
Keypad Column 3. Can be reconfigured as GPIO6.
21
C4
Keypad Column 4. Can be reconfigured as GPIO7.
22
KEYIRQ
Active-Low Keypad Interrupt. KEYIRQ is low when a key press is detected.
23
PENIRQ
Active-Low Pen Touch Interrupt. PENIRQ is low when a screen touch is detected.
24
DOUT
Serial Data Output. Data is clocked out at SCLK falling edge. High impedance when CS is high.
25
BUSY
Active-Low Busy Output. BUSY goes low and stays low during each functional operation. The host
controller should wait until BUSY is high again before using the serial interface.
26
DIN
Serial Data Input. Data is clocked in on the rising edge of SCLK.
Serial Clock Input. Clocks data in and out of the serial interface and sets the conversion speed (duty
cycle must be 30% to 70%).
27
SCLK
28
CS
Active-Low Chip Select. Data is not clocked into DIN unless CS is low. When CS is high, DOUT is
high impedance.
—
EP
Exposed Pad. Internally connected to GND. Connect to a large ground plane to maximize thermal
performance. Not intended as an electrical connection point.
*ESD protected: ±8kV Contact, ±15kV Air.
Detailed Description
The MAX1233/MAX1234 are 4-wire touch-screen controllers. Figure 1 shows the functional diagram of the
MAX1233/MAX1234. Each device includes a 12-bit sampling ADC, 8-bit voltage output DAC, keypad scanner
that can also be configured as a GPIO, internal clock,
reference, temperature sensor, two battery monitor
inputs, two auxiliary analog inputs, SPI/QSPI/
MICROWIRE-compatible serial interface, and low onresistance switches for driving touch screens.
The 16-bit register inside the MAX1233/MAX1234
allows for easy control and stores results that can be
read at any time. The BUSY output indicates that a
functional operation is in progress. The PENIRQ and
KEYIRQ outputs, respectively, indicate that a screen
touch or a key press has occurred.
Touch-Screen Operation
The 4-wire touch-screen controller works by creating a
voltage gradient across the vertical or horizontal resistive touch screen connected to the analog inputs of the
MAX1233/MAX1234, as shown in Figure 2. The voltage
across the touch-screen panels is applied through internal MOSFET switches that connect each resistive layer
to AVDD and ground. For example, to measure the Y
position when a pointing device presses on the touch
screen, the Y+ and Y- drivers are turned on, connecting
one side of the vertical resistive layer to AVDD and the
other side to ground. The horizontal resistive layer functions as a sense line. One side of this resistive layer gets
connected to the X+ input, while the other side is left
12
open or floating. The point where the touch screen is
pressed brings the two resistive layers in contact and
creates a voltage-divider at that point. The data converter senses the voltage at the point of contact through the
X+ input and digitizes it.
12-Bit ADC
Analog Inputs
Figure 3 shows a block diagram of the ADC’s analog
input section including the input multiplexer, the differential input, and the differential reference. The input multiplexer switches between X+, X-, Y+, Y-, AUX1, AUX2,
BAT1, BAT2, and the internal temperature sensor.
The time required for the T/H to acquire an input signal
is a function of how quickly its input capacitance is
charged. If the input signal’s source impedance is high,
the acquisition time lengthens, and more time must be
allowed. The acquisition time (tACQ) is the maximum
time the device takes to acquire the input signal to 12bit accuracy. Configure tACQ by writing to the ADC
control register. See Table 1 for the maximum input signal source impedance (RSOURCE) for complete settling
during acquisition.
Accommodate higher source impedances by placing a
0.1µF capacitor between the analog input and GND.
Input Bandwidth
The ADC’s input-tracking circuitry has a 0.5MHz smallsignal bandwidth. To avoid high-frequency signals
being aliased into the frequency band of interest, antialias filtering is recommended.
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
C2
C3
C4
R1
R2
R3
MAX1233/MAX1234
C1
R4
KEYPAD CONTROLLER
AND GPIO
OSCILLATOR
MAX1233
MAX1234
REGISTERS AND
SCAN STATE
CONTROL
TEMP
SENSOR
DOUT
*X+
SCLK
*XX/Y SWITCHES
*Y+
SERIAL
DATA
I/O
MUX
12-BIT
ADC
*Y-
DIN
CS
PENIRQ
KEYIRQ
*BAT1
BATTERY MONITOR
*BAT2
BATTERY MONITOR
BUSY
*AUX1
*AUX2
INTERNAL
REFERENCE
2.5V/1.0V
REF
8-BIT
DAC
DACOUT
REF
DAC
*ESD PROTECTED
Figure 1. Block Diagram
Table 1. Maximum Input Source
Impedance
+AVDD
FORCE LINE
ACQUISITION RESOLUTION
TIME (µs)
(BITS)
Y+
SENSE LINE
+IN
+REF
-IN
-REF
X+
SENSE
LINE
FORCE LINE
Y-
GND
MAXIMUM RSOURCE FOR
COMPLETE SETTLING
DURING ACQUISITION (kΩ)
1.5
8
2.6
1.5
10
2.0
1.5
12
1.5
5.0
8
23
5.0
10
19
5.0
12
15
95
8
560
95
10
470
95
12
400
Figure 2. Touch-Screen Measurement
______________________________________________________________________________________
13
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
+AVDD
TEMP2
VREF
TEMP1
MAX1233
MAX1234
X+
XREF ON/OFF
+REF
Y+
+IN
Y-
CONVERTER
-IN
2.5V/1.0V
REFERENCE
-REF
7.5kΩ
VBAT1
7.5kΩ
VBAT2
2.5kΩ
2.5kΩ
BATTERY
ON
BATTERY
ON
AUX1
AUX2
GND
Figure 3. Simplified Diagram of Analog Input Section
Analog Input Protection
Internal protection diodes that clamp the analog input
to AVDD and GND allow the analog input pins to swing
from GND - 0.3V to AV DD + 0.3V without damage.
Analog inputs must not exceed AVDD by more than
50mV or be lower than GND by more than 50mV for
accurate conversions. If an off-channel analog input
voltage exceeds the supplies, limit the input current to
50mA. All analog inputs are also fully ESD protected
14
to ±8kV, using the Contact-Discharge method and
±15kV using the Air-Gap method specified in IEC1000-4-2.
Reference for ADC
Internal Reference
The MAX1233/MAX1234 offer an internal voltage reference for the ADC that can be set to +1.0V or +2.5V. The
MAX1233/MAX1234 typically use the internal reference
for battery monitoring, temperature measurement, and for
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
3R
2x
REF PIN
OPTIONAL
2R
Figure 4. Block Diagram of the Internal Reference
Full-Power Mode (RES1 = 0, RES0 = 1)
In the full-power mode, the RES1 bit is set LOW and
RES0 bit is set HIGH. In this mode, the device is powered up and the internal ADC reference is always ON.
The MAX1233/MAX1234 internal reference remains fully
powered after completing a scan.
Internal Clock
measurement of the auxiliary inputs. Figure 4 shows the
on-chip reference circuitry of the MAX1233/MAX1234.
Set the internal reference voltage by writing to the RFV
bits in the ADC control register (see Tables 4, 5, and 12).
The MAX1233/MAX1234 can accept an external reference connected to REF for ADC conversion.
The MAX1233/MAX1234 operate from an internal oscillator, which is accurate to within 20% of the 10MHz
specified clock rate. The internal oscillator controls the
timing of the acquisition, conversion, touch-screen settling, reference power-up, and keypad debounce times.
External Reference
The MAX1233/MAX1234 can accept an external reference connected to the REF pin for ADC conversions.
The internal reference should be disabled (RES1 = 1)
when using an external reference. At a conversion rate
of 50ksps, an external reference at REF must deliver up
to 15µA of load current and have 50Ω or less output
impedance. If the external reference has high output
impedance or is noisy, bypass it close to the REF pin
with a 0.1µF capacitor.
The MAX1233/MAX1234 have a voltage-output, true 8-bit
monotonic DAC with less than 1LSB integral nonlinearity
error and less than 1LSB differential nonlinearity error. It
requires a supply current of only 150µA (typ) and provides a buffered voltage output. The DAC is at midscale
code at power-up and remains there until a new code is
written to the DAC register. During shutdown, the DAC’s
output is pulled to ground with a 1MΩ load.
Selecting Internal or External Reference
Set the type of reference being used by programming
the ADC control register. To select the internal reference, clock zeros into bits [A/D3:A/D0] and a zero to bit
RES1, as shown in the Control Registers section. To
change to external reference mode, clock zeros into
bits [A/D3:A/D0] and a one to bit RES1. See Table 13
for more information about selecting an internal or
external reference for the ADC.
Reference Power Modes
Auto Power-Down Mode (RES1 = RES0 = 0)
The MAX1233/MAX1234 are in auto power-down mode
at initial power-up. Set the RES1 and RES0 bits to zero
to use the MAX1233/MAX1234 in the auto power-down
mode. In this mode, the internal reference is normally
off. When a command to perform a battery measure-
8-Bit DAC
The internal DAC can be used in various system applications such as LCD/TFT-bias control, automatic tuning
(VCO), power amplifier bias control, programmable
threshold levels, and automatic gain control (AGC).
The 8-bit DAC in the MAX1233/MAX1234 employs a
current-steering topology as shown in Figure 5. At the
core of this DAC is a reference voltage-to-current converter (V/I) that generates a reference current. This current is mirrored to 255 equally weighted current
sources. DAC switches control the outputs of these current mirrors so that only the desired fraction of the total
current-mirror currents is steered to the DAC output.
The current is then converted to a voltage across a
resistor, and the output amplifier buffers this voltage.
DAC Output Voltage
The 8-bit DAC code is binary unipolar with 1LSB =
(VREF/256). The DAC has a full-scale output voltage of
(0.9 × AVDD - 1LSB).
______________________________________________________________________________________
15
MAX1233/MAX1234
+1.25V
BANDGAP
ment, temperature measurement, or auxiliary input
measurement is written to the ADC control register, the
device powers on the internal reference, waits for the
internal reference to settle, completes the requested
scan, and powers down the internal reference. The reference power delay depends upon the ADC resolution
selected (see Table 8). Do not bypass REF with an
external capacitor when performing scans in auto
power-down mode.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
+AVDD
VREF
1MΩ
SW1
SW2
SW255
S1
OUT
TOUCH-SCREEN
DETECTOR
TOUCH
SCREEN
PENIRQ
X+
Y+
Figure 5. DAC Current-Steering Topology
Output Buffer
The DAC voltage output is an internally buffered unitygain follower that slews at up to ±0.4V/µs. The output
can swing from zero to full scale. With a 1/4FS to 3/4FS
output transition, the amplifier output typically settles to
1/2LSB in less than 5µs when loaded with 10kΩ in parallel with 50pF. The buffer amplifier is stable with any
combination of resistive loads >10kΩ and capacitive
loads <50pF.
Power-On Reset
All registers of the MAX1233/MAX1234 power up at a
default zero state, except the DAC data register, which
is set to 10000000, so the output is at midscale.
Keypad Controller and GPIO
The keypad controller is designed to interface a matrixtype 4 rows × 4 columns (16 keys or fewer) keypad to a
host controller. The KEY control register controls keypad
interrupt, keypad scan, and keypad debounce times.
The KeyMask and ColumnMask registers enable masking of a particular key or an entire column of the keypad
when they are not in use. The MAX1233/MAX1234 offer
two keypad data registers. KPData1 is the pending register. KPData2 holds keypad scan results of only the
unmasked keys. If 12 or fewer keys are being monitored,
one or more of the row/column pins of the
MAX1233/MAX1234 can be software programmed as
GPIO pins.
Touch-Screen Detection
Touch-screen detection can be enabled or disabled by
writing to the ADC control register as shown in Table 4.
Touch-screen detection is disabled at initial power-up.
Once touch-screen detection is enabled, the Y- driver
is on and the Y- pin is connected to GND. The X+ pin is
internally pulled to AVDD through a 1MΩ resistor as
16
XY-
S2
Figure 6. Touch-Screen Detection Block Diagram
shown in Figure 6. When the screen is touched, the X+
pin is pulled to GND through the touch screen and a
touch is detected.
When the 1MΩ pullup resistor is first connected, the X+
pin can be floating near ground. To prevent false touch
detection in this case, the X+ pin is precharged high for
0.1µs using the 7Ω PMOS driver before touch detection
begins.
Key-Press Detection
Key-press detection can be enabled or disabled by
writing to the keypad control register as shown in Table
17. Key-press detection is disabled at initial power-up.
Once key-press detection is enabled, the C_ pins are
internally connected to DVDD and the R_ pins are internally pulled to GND through a 16kΩ resistor. When a
key is pressed, the associated row pin is pulled to
DVDD and the key press is detected. Figure 7 shows
the key-press detection circuitry.
Interrupts
PEN Interrupt Request (PENIRQ)
The PENIRQ output can be used to alert the host controller of a screen touch. The PENIRQ output is normally
high and goes low after a screen touch is detected.
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
SIMPLIFIED KEYPAD CIRCUITRY
DRIVERS PULL HIGH
OR GO THREE-STATE
C1
C2
C3
C4
R1
TO KEYPAD
WAKEUP AND
DEBOUNCE
LOGIC
KEYPAD
R2
R3
R4
Figure 7. Key-Press Detection Circuitry
X+
X+
PENIRQ
PENIRQ
BUSY
BUSY
CS
DATA
READ
CS
DATA
READ
DIN
DOUT
DOUT
TOUCHSCREEN
DATA
Figure 8a. Timing Diagram for Touch-Initiated Screen Scan
TOUCHSCREEN
DATA
Figure 8b. Timing Diagram for Host-Initiated Screen Scan
______________________________________________________________________________________
17
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
PENIRQ returns high only after a touch-screen scan is
completed. PENIRQ does not go low again until one of
the touch-screen data registers is read. Figures 8a and
8b show the timing diagrams for the PENIRQ pin.
Keypad Interrupt Request (KEYIRQ)
The KEYIRQ output can be used to alert the host controller of a key press. The KEYIRQ output is normally
high and goes low after a key press is detected.
KEYIRQ returns high only after a key-press scan is
completed. KEYIRQ does not go low again until one of
the key-press data registers is read. Figures 9a and 9b
show the timing diagrams for the KEYIRQ pin.
R_
KEYIRQ
BUSY
CS
DATA
READ
Busy Indicator (BUSY)
BUSY informs the host processor that a scan is in
progress. BUSY is normally high and goes low and
stays low during each functional operation. The host
controller should wait until BUSY is high again before
using the serial interface.
Digital Interface
The MAX1233/MAX1234 interface to the host controller
through a standard 3-wire serial interface at up to
10MHz. DIN and CS are the digital inputs to the
MAX1233/MAX1234. DOUT is the serial data output.
Data is clocked out at the SCLK falling edge and is
high impedance when CS is high. When performing an
ADC scan, CS must de-assert high before the end of
the first conversion, otherwise the conversion results
will not be stored. PENIRQ and KEYIRQ communicate
interrupts from the touch-screen and keypad controllers
to the host processor when a screen touch or a key
press is detected. BUSY informs the host processor that
a scan is in progress. In addition to these digital I/Os, the
row and column pins of the keypad controller can be
programmed as GPIO pins.
Communications Protocol
The MAX1233/MAX1234 are controlled by reading from
and writing to registers through the 3-wire serial interface. These registers are addressed through a 16-bit
command that is sent prior to the data. The command
is shown in Table 2.
The first 16 bits after the falling edge of CS contain the
command word. The command word begins with an
R/W bit, which specifies the direction of data flow on
the serial bus. Bits 14 through 7 are reserved for future
use. Bit 6 specifies the page of memory in which the
DOUT
TOUCHSCREEN
DATA
Figure 9a. Timing Diagram for Key-Press-Initiated Debounce
Scan
R_
KEYIRQ
BUSY
CS
DATA
READ
DIN
DOUT
TOUCHSCREEN
DATA
Figure 9b. Timing Diagram for Host-Initiated Keypad
Debounce Scan
desired register is located. The last 6 bits specify the
address of the desired register. The next 16 bits of data
are read from or written to the address specified in the
command word. After 32 clock cycles, the interface
automatically increments its address pointer and continues reading or writing until the rising edge of CS, or
until it reaches the end of the page.
Table 2. Command Word Format
BIT15
MSB
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
LSB
R/W
RES
RES
RES
RES
RES
RES
RES
RES
PAGE
ADD5
ADD4
ADD3
ADD2
ADD1
ADD0
18
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
WRITE
READ
COMMAND COMMAND
(HEX)
(HEX)
REGISTER
NAME
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
X0
—
0x8000
X
0
0
0
0
X11
X10
X9
X8
X7
X6
X5
X4
X3
X2
X1
—
0x8001
Y
0
0
0
0
Y11
Y10
Y9
Y8
Y7
Y6
Y5
Y4
Y3
Y2
Y1
Y0
—
0x8002
Z1
0
0
0
0
Z1_11
Z1_10
Z1_9
Z1_8
Z1_7
Z1_6
Z1_5
Z1_4
Z1_3
Z1_2
Z1_1
Z1_0
—
0x8003
Z2
0
0
0
0
Z2_11
Z2_10
Z2_9
Z2_8
Z2_7
Z2_6
Z2_5
Z2_4
Z2_3
Z2_2
Z2_1
Z2_0
—
0x8004
KPD
K15
K14
K13
K12
K11
K10
K9
K8
K7
K6
K5
K4
K3
K2
K1
K0
—
0x8005
BAT1
0
0
0
0
B1_11
B1_10
B1_9
B1_8
B1_7
B1_6
B1_5
B1_4
B1_3
B1_2
B1_1
B1_0
—
0x8006
BAT2
0
0
0
0
B2_11
B2_10
B2_9
B2_8
B2_7
B2_6
B2_5
B2_4
B2_3
B2_2
B2_1
B2_0
—
0x8007
AUX1
0
0
0
0
A1_11
A1_10
A1_9
A1_8
A1_7
A1_6
A1_5
A1_4
A1_3
A1_2
A1_1
A1_0
—
0x8008
AUX2
0
0
0
0
A2_11
A2_10
A2_9
A2_8
A2_7
A2_6
A2_5
A2_4
A2_3
A2_2
A2_1
A2_0
—
0x8009
TEMP1
0
0
0
0
T1_11
T1_10
T1_9
T1_8
T1_7
T1_6
T1_5
T1_4
T1_3
T1_2
T1_1
T1_0
—
0x800A
TEMP2
0
0
0
0
T2_11
T2_10
T2_9
T2_8
T2_7
T2_6
T2_5
T2_4
T2_3
T2_2
T2_1
T2_0
0x000B
0x800B
DAC data
0
0
0
0
0
0
0
0
DA7
DA6
DA5
DA4
DA3
DA2
DA1
DA0
0x000F
0x800F
GPIO data
GPD7
GPD6
GPD5
GPD4
GPD3
GPD2
GPD1
GPD0
0
0
0
0
0
0
0
0
—
0x8010
KPData1
K1_15
K1_14
K1_13
K1_12
K1_11
K1_10
K1_9
K1_8
K1_7
K1_6
K1_5
K1_4
K1_3
K1_2
K1_1
K1_0
—
0x8011
KPData2
K2_15
K2_14
K2_13
K2_12
K2_11
K2_10
K2_9
K2_8
K2_7
K2_6
K2_5
K2_4
K2_3
K2_2
K2_1
K2_0
0x0040
0x8040
ADC control
PENSTS
ADSTS
A/D3
A/D2
A/D1
A/D0
RES1
RES0
AVG1
AVG0
CNR1
CNR0
ST2
ST1
ST0
RFV
0x0041
0x8041
KEY control
KEYSTS1 KEYSTS0
DBN2
DBN1
DBN0
HLD2
HLD1
HLD0
0
0
0
0
0
0
0
0
0x0042
0x8042
DAC control
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0x004E
0x804E
GPIO pullup
PU7
PU6
PU5
PU4
PU3
PU2
PU1
PU0
0
0
0
0
0
0
0
0
0x004F
0x804F
GPIO control
GP7
GP6
GP5
GP4
GP3
GP2
GP1
GP0
OE7
OE6
OE5
OE4
OE3
OE2
OE1
OE0
DAPD
0
0x0050
0x8050
KPKeyMask
KM15
KM14
KM13
KM12
KM11
KM10
KM9
KM8
KM7
KM6
KM5
KM4
KM3
KM2
KM1
KM0
0x0051
0x8051
KPColumnMask
CM4
CM3
CM2
CM1
0
0
0
0
0
0
0
0
0
0
0
0
Note: All other registers are reserved and should always be 0. Power-on reset state is DAC data at midscale (0x0080), all other registers are 0.
______________________________________________________________________________________
19
MAX1233/MAX1234
Table 3. Register Summary
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
In order to read the entire first page of memory, for
example, the host processor must send the
MAX1233/MAX1234 the command 0x8000 H . The
MAX1233/MAX1234 then begin clocking out 16-bit data
starting with the X-data register. In order to write to the
second page of memory, the host processor sends the
MAX1233/MAX1234 the command 0x0040H. The succeeding data is then written in 16-bit words beginning
with the ADC control register. Figures 10a and 10b show
a complete write and read operation, respectively,
between the processor and the MAX1233/MAX1234.
Memory Map
The MAX1233/MAX1234s’ internal memory is divided
into two pages—one for data and one for control, each
of which contains thirty-two 16-bit registers.
Control Registers
Table 3 provides a summary of all registers and bit
locations of the MAX1233/MAX1234.
ADC Control Register
The ADC measures touch position, touch pressure, battery voltage, auxiliary analog inputs, and temperature.
The ADC control register determines which input is
selected and converted. Tables 4 and 5 show the format and bit descriptions for the ADC control register.
SCLK
WRITE OPERATION
CS
D0
D15
DIN
D15 IS READ/WRITE BIT
LOW FOR WRITE
DOUT
D0
D15
D15–D0 COMMAND WORD
D15–D0 DATA WORD
THREESTATE
THREESTATE
TIMING NOT TO SCALE.
Figure 10a. Timing Diagram of Write Operation
SCLK
READ OPERATION
CS
D15 D14
DIN
D0
D15–D0 COMMAND
WORD
DOUT
THREE-STATE
D0
D15
D15
DATA WORD
D0
THREE-STATE
DATA WORD
Figure 10b. Timing Diagram of Read Operation
Table 4. ADC Control Register (Write 0x0040/Read 0x8040)
BIT15
BIT14
BIT13 BIT12 BIT11 BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
PENSTS
ADSTS
A/D3
RES1
RES0
AVG1
AVG0
CNR1 CNR0
ST2
ST1
ST0
RFV
20
A/D2
A/D1
A/D0
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Bits 6-7: Converter Averaging Control
These bits specify the number of data averages the
converter performs. Table 9 shows how to program for
the desired number of averages. When averaging is
used, ADSTS and BUSY indicate the converter is busy
until all conversions needed for the averaging finish.
These bits are identical, regardless of read or write.
Bits 10-13: ADC Scan Select
These bits control which input to convert and which converter mode is used. The bits are identical regardless of a
read or write. See Table 7 for details about using these bits.
Bits 4-5: ADC Conversion Rate Control
These bits specify the internal conversion rate, which
the ADC uses to perform a single conversion, as shown
in Table 10. Lowering the conversion rate also reduces
power consumption. These bits are identical, regardless of read or write.
Bits 8-9: ADC Resolution Control
These bits specify the ADC resolution and are identical
regardless of read or write. Table 8 shows how to use
these bits to set the resolution.
Table 5. ADC Control Register Bit Descriptions (Write 0x0040/Read 0x8040)
BIT
NAME
15 (MSB)
PENSTS
DESCRIPTION
14
ADSTS
13
A/D3
Selects ADC scan functions
12
A/D2
Selects ADC scan functions
11
A/D1
Selects ADC scan functions
10
A/D0
Selects ADC scan functions
9
RES1
Controls ADC resolution
Read: pen interrupt status; Write: sets interrupt initiated touch-screen scans
Read: ADC status; Write: stops ADC
8
RES0
Controls ADC resolution
7
AVG1
Controls ADC result averaging
6
AVG0
Controls ADC result averaging
5
CNR1
Controls ADC conversion rate
4
CNR0
3
ST2
Controls touch-screen settling wait time
2
ST1
Controls touch-screen settling wait time
1
ST0
Controls touch-screen settling wait time
0 (LSB)
RFV
Chooses 1.0V or 2.5V reference
Controls ADC conversion rate
Table 6. ADSTS Bit Operation
PENSTS
ADSTS
READ FUNCTION
WRITE FUNCTION
0
0
No screen touch detected;
scan or conversion in progress
Performs one scan and waits to detect a screen touch. Upon
detection, issues an interrupt and waits until told to scan by the
host controller.
1
0
Screen touch detected;
scan or conversion in progress
Stops any ongoing scan and waits to detect a screen touch. Upon
detection, issues an interrupt and performs a scan.
0
1
No screen touch detected;
data available
Stops any ongoing scan and waits to detect a screen touch. Upon
detection, issues an interrupt and waits until told to scan by the
host controller.
1
1
Screen touch detected;
data available
Stops any ongoing scan and powers down the screen touch
detection circuit. No screen touches are detected in this mode.
______________________________________________________________________________________
21
MAX1233/MAX1234
Bits 14-15: Pen Interrupt Status and
ADC Status Bits
These bits are used to control or monitor ADC scans.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Table 7. ADC Scan Select (Touch Screen, Battery, Auxiliary Channels, and Temperature)
A/D3
A/D2
A/D1
A/D0
FUNCTION
0
0
0
0
Configures the ADC reference as selected by RES [1:0] bits as shown in Table 13. No measurement
is performed.
0
0
0
1
Measures X/Y touch position and returns results to the X and Y data registers.
0
0
1
0
Measures X/Y touch position and Z1/ Z2 touch pressure and returns results to the X, Y, Z1, and Z2
data registers.
0
0
1
1
Measures X touch position and returns results to the X data register.
0
1
0
0
Measures Y touch position and returns results to the Y data register.
0
1
0
1
Measures Z1/Z2 touch pressure and returns results to the Z1 and Z2 data register.
0
1
1
0
Measures Battery Input 1 through a 4:1 divider and returns results to the BAT1 data register.
0
1
1
1
Measures Battery Input 2 through a 4:1 divider and returns results to the BAT2 data register.
1
0
0
0
Measures Auxiliary Input 1 and returns results to the AUX1 data register.
1
0
0
1
Measures Auxiliary Input 2 and returns results to the AUX2 data register.
1
0
1
0
Measures temperature (single ended) and returns results to the TEMP1 data register.
1
0
1
1
Measures Battery Input 1, Battery Input 2, Auxiliary Input 1, Auxiliary Input 2, and temperature
(differential), and returns results to the appropriate data registers.
1
1
0
0
Measures temperature (differential) and returns results to the TEMP1 and TEMP2 data registers.
1
1
0
1
Turns on Y+, Y- drivers. No measurement is performed.
1
1
1
0
Turns on X+, X- drivers. No measurement is performed.
1
1
1
1
Turns on Y+, X- drivers. No measurement is performed.
Table 8. ADC Resolution Control
RES1
RES0
ADC
RESOLUTION
INTERNALLY TIMED
REFERENCE POWER-UP
DELAY* (µs)
0
0
8 bit
31
0
1
8 bit
31
1
0
10 bit
37
1
1
12 bit
44
*Applicable only for temperature, battery, or auxiliary
measurements in auto power-up reference mode.
Table 10. ADC Conversion Rate Control
CNR1
CNR0
FUNCTION
0
0
3.5µs/sample
(1.5µs acquisition, 2µs conversion)
0
1
3.5µs/sample
(1.5µs acquisition, 2µs conversion)
1
0
10µs/sample
(5µs acquisition, 5µs conversion)
1
1
100µs/sample
(95µs acquisition, 5µs conversion)
Table 9. ADC Averaging Control
AVG1
AVG0
FUNCTION
0
0
No data averages (default)
0
1
4 data averages
1
0
8 data averages
1
1
16 data averages
22
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Internal ADC Reference Power-Down Control
The ADC control register controls the power setting of
the internal ADC reference. Zeros must be written to
bits A/D3–A/D0 to control internal reference power-up
followed by the appropriate logic at the RES1 and RES0
bits. Table 13 shows the internal ADC reference powerdown control.
Bit 0: ADC Internal Reference Voltage Control
This bit selects the ADC internal reference voltage,
either +1.0V or +2.5V. This bit is identical, regardless of
read or write. The reference control bit is shown in
Table 12.
DAC Control Register
The MSB in this control register determines the powerdown control of the on-board DAC. Table 14 shows the
DAC control register. Writing a zero to bit 15 (DAPD)
powers up the DAC, while writing a 1 powers down the
DAC. Table 15 describes the DAC control register contents, while Table 16 shows the DAC power-down bit.
Table 11. Touch-Screen Settling Time
Control*
Keypad Control Registers
The keypad control register, keypad mask register, and
keypad column mask control register control the keypad scanner in the MAX1233/MAX1234. The keypad
control register (Table 17) controls scanning and
debouncing, while the keypad mask register (Table 22)
and the keypad column mask control register (Table 24),
ST2
ST1
ST0
0
0
0
Settling time: 0µs
SETTLING TIME
0
0
1
Settling time: 100µs
0
1
0
Settling time: 500µs
0
1
1
Settling time: 1ms
1
0
0
Settling time: 5ms
1
0
1
Settling time: 10ms
1
1
0
Settling time: 50ms
BIT
NAME
DESCRIPTION
1
1
1
Settling time: 100ms
15 (MSB)
DAPD
DAC powered down
[14:0]
0
Reserved
Table 15. DAC Control Register
Descriptions
*Applicable only for X, Y, Z1, and Z2 measurements.
Table 12. ADC Reference Control Bit
Table 16. DAC Power-Down Bit
DAPC
FUNCTION
0
+1.0V reference
0
DAC powered up
1
+2.5V reference
1
DAC powered down
RFV
FUNCTION
Table 13. Internal ADC Reference Auto Power-Up Control
[A/D3:A/D0]
RES1
RES0
ADC REFERENCE
SOURCE
0000
0
0
Internal
ADC REFERENCE POWER MODE
Power up, wait for reference to settle, and power down again for
each temperature, battery, or auxiliary scan (auto power-up mode)
0000
0
1
Internal
Always powered up
0000
1
0
External
Always powered down
0000
1
1
External
Always powered down
Table 14. DAC Control Register (Write 0x0042/Read 0x8042)
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
DAPD
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
______________________________________________________________________________________
23
MAX1233/MAX1234
Bits 1-3: Touch-Screen Settling Time Control
These bits specify the time delay from pen-touch detection to a conversion start. This allows the selection of the
appropriate settling time for the touch screen being used.
Table 11 shows how to set the settling time. These bits
are identical, regardless of read or write.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Table 17. Keypad Control Register (Write 0x0041/Read 0x8041)
BIT15
BIT14
KEYSTS1
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
KEYSTS0 DBN2
DBN1
DBN0
HLD2
HLD
HLD
0
0
0
0
0
0
0
0
Table 18. Keypad Control Register Bit Descriptions (Write 0x0041/Read 0x8041)
BIT
NAME
15 (MSB)
KEYSTS1
Read: keypad interrupt status; Write: set interrupt initiated keypad scans
DESCRIPTION
14
KEYSTS0
Read: keypad scan status; Write: stop keypad scan
13
DBN2
Keypad debounce time control
12
DBN1
Keypad debounce time control
11
DBN0
Keypad debounce time control
10
HLD2
Keypad hold time control
9
HLD1
Keypad hold time control
8
HLD0
[7:0]
0
Keypad hold time control
Reserved
Table 19. KEYSTS1/KEYSTS0 Functions
KEYSTS1
KEYSTS0
READ FUNCTION
WRITE FUNCTION
0
0
No button press detected;
scan or debounce in progress
Scans keypad once and waits to detect a button press. Upon
detection, issues an interrupt and waits for the host’s instruction
before scanning.
1
0
Button press detected;
scan or debounce in progress
Stops any ongoing scan and waits to detect a button press. Upon
detection, issues an interrupt and scans the keypad.
0
1
No button press detected;
data available
Stops any ongoing scan and waits to detect a button press. Upon
detection, issues an interrupt and waits for the host’s instruction
before scanning.
1
1
Button press detected;
data available
Stops any ongoing scan and powers down the button press
detection circuit. No button presses are detected in this mode.
Table 20. Keypad Debounce Time Control
DBN2
DBN1
DBN0
0
0
0
Debounce time: 2
0
0
1
Debounce time: 10
0
1
0
Debounce time: 20
0
1
1
Debounce time: 50
1
0
0
Debounce time: 60
1
0
1
Debounce time: 80
1
1
0
Debounce time: 100
1
1
1
Debounce time: 120
24
FUNCTION (ms)
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
GPIO Control Register
The GPIO control register and the GPIO pullup register
allow the keypad controller’s row and column inputs to be
configured as up to eight parallel I/O pins. Tables 26 and
27 show the GPIO control register layout and control register descriptions. Tables 28 and 29 show the GPIO pullup
disable register and associated descriptions. For more
information, see the Applications Information section.
Table 21. Keypad Hold Time Control
HLD2
HLD1
HLD0
0
0
0
If a button is held, wait 100µs before beginning next debounce scan
FUNCTION
0
0
1
If a button is held, wait 1 debounce time before beginning the next debounce scan
0
1
0
If a button is held, wait 2 debounce times before beginning the next debounce scan
0
1
1
If a button is held, wait 3 debounce times before beginning the next debounce scan
1
0
0
If a button is held, wait 4 debounce times before beginning the next debounce scan
1
0
1
If a button is held, wait 5 debounce times before beginning the next debounce scan
1
1
0
If a button is held, wait 6 debounce times before beginning the next debounce scan
1
1
1
If a button is held, wait 7 debounce times before beginning the next debounce scan
Table 22. Keypad Key Mask Register Bit Descriptions (Write 0x0050/Read 0x8050)
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
KM15
KM14
KM13
KM12
KM11
KM10
KM9
KM8
KM7
KM6
KM5
KM4
KM3
KM2
KM1
KM0
Table 23. Keypad Key Mask Register Bit Descriptions (Write 0x0050/Read 0x8050)
BIT
NAME
DESCRIPTION
15
KM15
Mask status register data update on individual key for row 4, column 4
14
KM14
Mask status register data update on individual key for row 3, column 4
13
KM13
Mask status register data update on individual key for row 2, column 4
12
KM12
Mask status register data update on individual key for row 1, column 4
11
KM11
Mask status register data update on individual key for row 4, column 3
10
KM10
Mask status register data update on individual key for row 3, column 3
9
KM9
Mask status register data update on individual key for row 2, column 3
8
KM8
Mask status register data update on individual key for row 1, column 3
7
KM7
Mask status register data update on individual key for row 4, column 2
6
KM6
Mask status register data update on individual key for row 3, column 2
5
KM5
Mask status register data update on individual key for row 2, column 2
4
KM4
Mask status register data update on individual key for row 1, column 2
3
KM3
Mask status register data update on individual key for row 4, column 1
2
KM2
Mask status register data update on individual key for row 3, column 1
1
KM1
Mask status register data update on individual key for row 2, column 1
0
KM0
Mask status register data update on individual key for row 1, column 1
Table 24. Keypad Column Mask Register (Write 0x0051/Read 0x8051)
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
CM4
CM3
CM2
CM1
0
0
0
0
0
0
0
0
0
0
0
0
______________________________________________________________________________________
25
MAX1233/MAX1234
allowing certain keys to be masked from detection.
Tables 18–21 show the programmable bits of the keypad
control register. Tables 23, 24, and 25 show the programmable bits of the keypad mask registers. The Keypad
Controller and GPIO section provides more details.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Table 25. Keypad Column Mask Register Bit Descriptions (Write 0x0051/Read 0x8051)
BIT
NAME
15
CM4
Mask interrupt, status register, and pending register data update on all keys in column 4
DESCRIPTION
14
CM3
Mask interrupt, status register, and pending register data update on all keys in column 3
13
CM2
Mask interrupt, status register, and pending register data update on all keys in column 2
12
CM1
Mask interrupt, status register, and pending register data update on all keys in column 1
[11:0]
0
Reserved
Table 26. GPIO Control Register (Write 0x004F/Read 0x804F)
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
GP7
GP6
GP5
GP4
GP3
GP2
GP1
GP0
OE7
OE6
OE5
OE4
OE3
OE2
OE1
OE0
Table 27. GPIO Control Register Bit Descriptions (Write 0x004F/Read 0x804F)
DESCRIPTION
BIT
NAME
15
GP7
C4 pin becomes GPIO pin 7
C4 pin remains keypad column 4
14
GP6
C3 pin becomes GPIO pin 6
C3 pin remains keypad column 3
13
GP5
C2 pin becomes GPIO pin 5
C2 pin remains keypad column 2
12
GP4
C1 pin becomes GPIO pin 4
C1 pin remains keypad column 1
11
GP3
R4 pin becomes GPIO pin 3
R4 pin remains keypad row 4
10
GP2
R3 pin becomes GPIO pin 2
R3 pin remains keypad row 3
9
GP1
R2 pin becomes GPIO pin 1
R2 pin remains keypad row 2
8
GP0
R1 pin becomes GPIO pin 0
R1 pin remains keypad row 1
[7:0]
[OE7:OE0]
GPIO pin configured as an output
GPIO pin configured as an input
1
0
Table 28.GPIO Pullup Disable Register (Write 0x004E/Read 0x804E)
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
PU7
PU6
PU5
PU4
PU3
PU2
PU1
PU0
0
0
0
0
0
0
0
0
Table 29. GPIO Pullup Disable Register
Descriptions
BIT
NAME
DESCRIPTION
[15:8]
[PU7:PU0]
1: Pullup disabled. Open collector output.
0: Pullup enabled.
[7:0]
0
Reserved: always write as zero.
Data Registers
The data results from conversions or keypad scans are
held in the data registers of the MAX1233/MAX1234.
During power-up, all of these data registers with the
exception of the DAC data register default to 0000H.
The DAC register defaults to 1000H.
26
Analog Input Data Registers
Table 30 shows the format of the X, Y, Z1, Z2, BAT1,
BAT2, AUX1, AUX2, TEMP1, and TEMP2 data registers.
The data format for these registers is right justified
beginning with bit 11. Data written through the serial
interface to these registers is not stored.
Keypad Data Registers
Table 31 shows the formatting of the keypad data registers, while Tables 32, 33, and 34 provide individual register bit descriptions. These registers have the same
format as the keypad mask register. Each bit represents one key on the keypad. Table 35 shows a map of
a 16-key keypad. Data written through the serial interface to these registers is not stored.
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
READ
REGISTER
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9
COMMAND NAME
0x8000
X
0
0
0
0
0x8001
Y
0
0
0
0x8002
Z1
0
0
0
0x8003
Z1
0
0
0x8005
BATT1
0
0x8006
BATT2
0
0x8007
AUX1
0x8008
AUX2
0x8009
0x800A
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
X11
X10
X9
X8
X7
X6
X5
X4
X3
X2
X1
X0
0
Y11
Y10
Y9
Y8
Y7
Y6
Y5
Y4
Y3
Y2
Y1
Y0
0
Z1_11 Z1_10 Z1_9 Z1_8 Z1_7 Z1_6 Z1_5 Z1_4 Z1_3 Z1_2 Z1_1 Z1_0
0
0
Z2_11 Z2_10 Z2_9 Z2_8 Z2_7 Z2_6 Z2_5 Z2_4 Z2_3 Z2_2 Z2_1 Z2_0
0
0
0
B1_11 B1_10 B1_9 B1_8 B1_7 B1_6 B1_5 B1_4 B1_3 B1_2 B1_1 B1_0
0
0
0
B2_11 B2_10 B2_9 B2_8 B2_7 B2_6 B2_5 B2_4 B2_3 B2_2 B2_1 B2_0
0
0
0
0
A1_11 A1_10 A1_9 A1_8 A1_7 A1_6 A1_5 A1_4 A1_3 A1_2 A1_1 A1_0
0
0
0
0
A2_11 A2_10 A2_9 A2_8 A2_7 A2_6 A2_5 A2_4 A2_3 A2_2 A2_1 A2_0
TEMP1
0
0
0
0
T1_11 T1_10 T1_9 T1_8 T1_7 T1_6 T1_5 T1_4 T1_3 T1_2 T1_1 T1_0
TEMP2
0
0
0
0
T2_11 T2_10 T2_9 T2_8 T2_7 T2_6 T2_5 T2_4 T2_3 T2_2 T2_1 T2_0
Table 31. Keypad Data Registers
READ
REGISTER
BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8 BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
COMMAND NAME
0x8004
KPD
K15
K14
K13
K12
K11
K10
K9
K8
K7
K6
K5
K4
K3
K2
K1
K0
0x8010
KPData1
(column K1_15 K1_14 K1_13 K1_12 K1_11 K1_10 K1_9 K1_8 K1_7 K1_6 K1_5 K1_4 K1_3 K1_2 K1_1 K1_0
maskable)
0x8011
KPData2
(key
K2_15 K2_14 K2_13 K2_12 K2_11 K2_10 K2_9 K2_8 K2_7 K2_6 K2_5 K2_4 K2_3 K2_2 K2_1 K2_0
maskable)
Table 32. Keypad Data Register Descriptions
BIT
NAME
DESCRIPTION
15
K15
Keypad scan result for row 4, column 4. Can only be masked by column mask.
14
K14
Keypad scan result for row 3, column 4. Can only be masked by column mask.
13
K13
Keypad scan result for row 2, column 4. Can only be masked by column mask.
12
K12
Keypad scan result for row 1, column 4. Can only be masked by column mask.
11
K11
Keypad scan result for row 4, column 3. Can only be masked by column mask.
10
K10
Keypad scan result for row 3, column 3. Can only be masked by column mask.
9
K9
Keypad scan result for row 2, column 3. Can only be masked by column mask.
8
K8
Keypad scan result for row 1, column 3. Can only be masked by column mask.
7
K7
Keypad scan result for row 4, column 2. Can only be masked by column mask.
6
K6
Keypad scan result for row 3, column 2. Can only be masked by column mask.
5
K5
Keypad scan result for row 2, column 2. Can only be masked by column mask.
4
K4
Keypad scan result for row 1, column 2. Can only be masked by column mask.
3
K3
Keypad scan result for row 4, column 1. Can only be masked by column mask.
2
K2
Keypad scan result for row 3, column 1. Can only be masked by column mask.
1
K1
Keypad scan result for row 2, column 1. Can only be masked by column mask.
0
K0
Keypad scan result for row 1, column 1. Can only be masked by column mask.
______________________________________________________________________________________
27
MAX1233/MAX1234
Table 30. Analog Inputs Data Register Format
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Table 33. Keypad Data Register 1 (Pending Register) Descriptions
BIT
NAME
15
K1_15
Keypad scan result for row 4, column 4. Can only be masked by column mask.
DESCRIPTION
14
K1_14
Keypad scan result for row 3, column 4. Can only be masked by column mask.
13
K1_13
Keypad scan result for row 2, column 4. Can only be masked by column mask.
12
K1_12
Keypad scan result for row 1, column 4. Can only be masked by column mask.
11
K1_11
Keypad scan result for row 4, column 3. Can only be masked by column mask.
10
K1_10
Keypad scan result for row 3, column 3. Can only be masked by column mask.
9
K1_9
Keypad scan result for row 2, column 3. Can only be masked by column mask.
8
K1_8
Keypad scan result for row 1, column 3. Can only be masked by column mask.
7
K1_7
Keypad scan result for row 4, column 2. Can only be masked by column mask.
6
K1_6
Keypad scan result for row 3, column 2. Can only be masked by column mask.
5
K1_5
Keypad scan result for row 2, column 2. Can only be masked by column mask.
4
K1_4
Keypad scan result for row 1, column 2. Can only be masked by column mask.
3
K1_3
Keypad scan result for row 4, column 1. Can only be masked by column mask.
2
K1_2
Keypad scan result for row 3, column 1. Can only be masked by column mask.
1
K1_1
Keypad scan result for row 2, column 1. Can only be masked by column mask.
0
K1_0
Keypad scan result for row 1, column 1. Can only be masked by column mask.
Table 34. Keypad Data Register 2 (Status Register) Descriptions
28
BIT
NAME
15
K2_15
Keypad scan result for row 4, column 4. Can be masked by key mask or column mask.
DESCRIPTION
14
K2_14
Keypad scan result for row 3, column 4. Can be masked by key mask or column mask.
13
K2_13
Keypad scan result for row 2, column 4. Can be masked by key mask or column mask.
12
K2_12
Keypad scan result for row 1, column 4. Can be masked by key mask or column mask.
11
K2_11
Keypad scan result for row 4, column 3. Can be masked by key mask or column mask.
10
K2_10
Keypad scan result for row 3, column 3. Can be masked by key mask or column mask.
9
K2_9
Keypad scan result for row 2, column 3. Can be masked by key mask or column mask.
8
K2_8
Keypad scan result for row 1, column 3. Can be masked by key mask or column mask.
7
K2_7
Keypad scan result for row 4, column 2. Can be masked by key mask or column mask.
6
K2_6
Keypad scan result for row 3, column 2. Can be masked by key mask or column mask.
5
K2_5
Keypad scan result for row 2, column 2. Can be masked by key mask or column mask.
4
K2_4
Keypad scan result for row 1, column 2. Can be masked by key mask or column mask.
3
K2_3
Keypad scan result for row 4, column 1. Can be masked by key mask or column mask.
2
K2_2
Keypad scan result for row 3, column 1. Can be masked by key mask or column mask.
1
K2_1
Keypad scan result for row 2, column 1. Can be masked by key mask or column mask.
0
K2_0
Keypad scan result for row 1, column 1. Can be masked by key mask or column mask.
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
GPIO Data Register
Tables 37 and 38 show the format and descriptions for
the GPIO data register. The register is left justified with
data in bit 15–bit 8. Reading the GPIO data register
gives the state of the R_ and C_ pins. Data written to
the GPIO data register appears on those R_ and C_
pins, which are configured as general-purpose outputs.
Data written to pins not configured as general-purpose
outputs is not stored.
ADC Transfer Function
Applications Information
Programmable 8-/10-/12-Bit Resolution
The MAX1233/MAX1234 provide the option of three different resolutions for the ADC: 8, 10, or 12 bits. Lower
resolutions are practical for some measurements such
as touch pressure. Lower resolution conversions have
smaller conversion times and therefore consume less
power. Program the resolution of the MAX1233/
MAX1234 12-bit ADCs by writing to the RES1 and RES0
bits in the ADC control register. When the MAX1233/
MAX1234 power up, both bits are set to zero so the resolution is set to 8 bits with a 31µs internally timed reference power-up delay as indicated by the ADC
resolution control table. As explained in the control register section, the RES1 and RES0 bits control the refer-
The MAX1233/MAX1234 output data is in straight binary format as shown in Figure 11. This figure shows the
ideal output code for the given input voltage and does
not include the effects of offset error, gain error, noise,
or nonlinearity.
OUTPUT CODE
MAX1233
MAX1234
FULL-SCALE
TRANSITION
11 ... 111
11 ... 110
11 ... 101
Table 35. Keypad to Key Bit Mapping
COMPONENT
FS = VREF
C1
C2
C3
C4
R1
K0
K4
K8
K12
00 ... 011
R2
K1
K5
K9
K13
00 ... 010
R3
K2
K6
K10
K14
00 ... 001
R4
K3
K7
K11
K15
00 ... 000
ZS = GND
1LSB = VREF
4096
0
1
2 3
INPUT VOLTAGE (LSB)
FS
FS - 3/2LSB
Figure 11. Ideal Input Voltages and Output Codes
Table 36. DAC Data Register(Write 0x000B/Read 0x800B)
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
0
0
0
0
0
0
0
0
DA7
DA6
DA5
DA4
DA3
DA2
DA1
DA0
Table 37. GPIO Data Register (Write 0x000F/Read 0x800F)
BIT15
BIT14
BIT13
BIT12
BIT11
BIT10
BIT9
BIT8
BIT7
BIT6
BIT5
BIT4
BIT3
BIT2
BIT1
BIT0
GPD7
GPD6
GPD5
GPD4
GPD3
GPD2
GPD1
GPD0
0
0
0
0
0
0
0
0
Table 38. GPIO Data Register Bit Descriptions (Write 0x000F/Read 0x800F)
BIT
NAME
15...8
GPD7...0
7...0
0
DESCRIPTION
GPIO data bits for GPIO pins 7...0
Reserved
______________________________________________________________________________________
29
MAX1233/MAX1234
DAC Data Register
The DAC data register stores data that is to be written
to the 8-bit DAC. Table 36 shows the configuration of
the DAC data register. It is right justified with bit 7–bit 0
storing the input data.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
+AVDD
FORCE LINE
Y+
SENSE LINE
X+
+REF
CONVERTER
-IN
-REF
+IN
SENSE LINE
FORCE LINE
Touch-Pressure Measurement
Y-
GND
Figure 12. Ratiometric Y-Coordinate Measurement
ence power-up status when the A/D0–A/D3 bits are
zero. These values can be set initially on power-up.
(Subsequently A/D0–A/D3 bits are not zero, and any
other value of these bits is exclusive to ADC resolution
programming.)
Differential Ratiometric Touch-Position
Measurement
The MAX1233/MAX1234 provide differential conversions. Figure 12 shows the switching matrix configuration for Y coordinate measurement. The +REF and -REF
inputs are connected directly to Y+ and Y-. The conversion result is a percentage of the external resistances,
and is unaffected by variation in the total touch-screen
resistance or the on-resistance of the internal switching
matrix. The touch screen remains powered during the
acquisition and conversion process.
Touch-Screen Settling
There are two mechanisms that affect the voltage level
at the point where the touch panel is pressed. One is
electrical ringing due to parasitic capacitance between
the top and bottom layers of the touch screen and the
other is the mechanical bouncing caused by vibration
of the top layer of the touch screen. Thus, the input sig-
30
nal, reference, or both may not settle into their final
steady-state values before the ADC samples the inputs,
and the reference voltage may continue to change during the conversion cycle. The MAX1233/MAX1234 can
be programmed to wait for a fixed amount of time after
a screen touch has been detected before beginning a
scan. Use the touch-screen settling control bits in the
ADC control register (Table 11) to set the settling delay
to between zero and 100ms.
The settling problem is amplified in some applications
where external filter capacitors may be required across
the touch screen to filter noise that may be generated
by the LCD panel or backlight circuitry, etc. The values
of these capacitors cause an additional settling time
requirement when the panel is touched. Any failure to
settle before conversion start may show up as a gain
error. Average the conversion result by writing to the
ADC control register, as shown in Table 10, to minimize
noise.
The MAX1233/MAX1234 provide two methods of measurement of the pressure applied to the touch screen.
Although 8-bit resolution is typically sufficient, the following calculations use 12-bit resolution demonstrating the
maximum precision of the MAX1233/MAX1234. Figure 13
shows the pressure measurement block diagram.
The first method performs pressure measurements
using a known X-plate resistance. After completing
three conversions, X-position, Z1-position, and Z2 position, use the following equation to calculate RTOUCH :
⎛X
⎞ ⎡⎛ Z ⎞ ⎤
RTOUCH = RXPLATE × ⎜ POSITION ⎟ × ⎢⎜ 2 ⎟ − 1⎥
⎝ 4096 ⎠ ⎢⎣⎝ Z1 ⎠ ⎥⎦
(
)
The second method requires knowing both the X-plate
and Y-plate resistance. Three touch-screen conversions are required in this method as well for measurement of the X-position, Y-position, and Z- position of the
touch screen. Use the following equation to calculate
RTOUCH:
⎧⎛
⎞ ⎛X
⎞ ⎡⎛ 4096 ⎞ ⎤ ⎫⎪
⎪ R
RTOUCH = ⎨⎜ XPLATE ⎟ × ⎜ POSITION ⎟ × ⎢⎜
⎟ − 1⎥ ⎬
Z1 ⎠ ⎝ 4096 ⎠ ⎢⎣⎝ Z1 ⎠ ⎥⎦ ⎪
⎩⎪⎝
⎭
⎧⎪
⎛Y
⎞ ⎫⎪
− ⎨RYPLATE × ⎜ POSITION ⎟ ⎬
⎝ 4096 ⎠ ⎪⎭
⎪⎩
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
SENSE LINE
X+
MEASURE X-POSITION
HOST WRITES
ADC
CONTROL REGISTER
Y+
MAX1233/MAX1234
FORCE LINE
BATTERY INPUT 1 OR
BATTERY INPUT 2
TOUCH
START CLOCK
V
X-POSITION
XFORCE LINE
MEASURE Z1-RESISTANCE
SET BUSY
LOW
YOPEN CIRCUIT
SENSE LINE
FORCE LINE
X+
Y+
NO
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
TOUCH
V
YES
Z1-RESISTANCE
POWER UP REFERENCE
X-
YOPEN CIRCUIT
FORCE LINE
POWER UP
ADC
FORCE LINE
OPEN CIRCUIT
X+
POWER DOWN
ADC
Y+
CONVERT
BATTERY INPUT 1 OR 2
TOUCH
POWER DOWN REFERENCE
V
Z2-RESISTANCE
SET BUSY HIGH
FORCE LINE
X-
Y-
SENSE LINE
MEASURE Z2-RESISTANCE
NO
IS DATA
AVERAGING DONE?
TURN OFF CLOCK
Figure 13. Pressure Measurement Block Diagram
YES
DC/DC
CONVERTER
BATTERY
0.5V TO
6.0V
DONE
2.7V
STORE BATTERY INPUT 1 OR 2 IN
BAT1 OR BAT2 REGISTER
AVDD
VBAT
7.5kΩ
Figure 15. Battery Voltage-Reading Flowchart
Battery-Voltage Monitors
0.125V TO 1.5V
CONVERTER
2.5kΩ
Figure 14. Battery Measurement Block Diagram
Two dedicated analog inputs (BAT1 and BAT2) allow the
MAX1233/MAX1234 to monitor the battery voltages prior
to the DC/DC converter. Figure 14 shows the battery voltage monitoring circuitry. The MAX1233/ MAX1234 directly monitor battery voltages from 0.5V to 6V. An internal
resistor network divides down BAT1 and BAT2 by 4 so
that a 6V battery voltage results in a 1.5V input to the
ADC. To minimize power consumption, the divider is only
enabled during the sampling of BAT1 and BAT2. Figure
15 illustrates the process of battery input reading.
______________________________________________________________________________________
31
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Auxiliary Analog Inputs
Two auxiliary analog inputs (AUX1 and AUX2) allow the
MAX1233/MAX1234 to monitor analog input voltages
from zero to VREF. Figure 16 illustrates the process of
auxiliary input reading.
HOST WRITES
ADC
CONTROL REGISTER
START CLOCK
Temperature Measurements
The MAX1233/MAX1234 provide two temperature measurement options: a single-ended conversion method
and a differential conversion method. Both temperature
measurement techniques rely on the semiconductor
junction’s operational characteristics at a fixed current
level. The forward diode voltage (VBE) vs. temperature is
a well-defined characteristic. The ambient temperature
can be predicted in applications by knowing the value
of the VBE voltage at a fixed temperature and then monitoring the delta of that voltage as the temperature
changes. Figure 17 illustrates the functional block of the
internal temperature sensor.
The single conversion method requires calibration at a
known temperature, but only requires a single reading to
predict the ambient temperature. First, the internal diode
forward bias voltage is measured by the ADC at a
known temperature. Subsequent diode measurements
provide an estimate of the ambient temperature through
extrapolation. This assumes a temperature coefficient of
-2.1mV/°C. The single conversion method results in a
resolution of 0.29°C/LSB (2.5V reference) and
0.12°C/LSB (1.0V reference) with a typical accuracy of
±2°C. Figure 18 shows the flowchart for the single temperature measurement.
The differential conversion method uses two measurement points. The first measurement is performed with a
fixed bias current into the internal diode. The second
measurement is performed with a fixed multiple of the
original bias current. The voltage difference between the
first and second conversion is proportional to the
absolute temperature and is expressed by the following
formula:
ΔVBE = (kT/q) ✕ ln(N)
SET BUSY
LOW
NO
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
YES
POWER UP REFERENCE
POWER UP
ADC
POWER DOWN
ADC
CONVERT
AUXILIARY INPUT 1 OR 2
POWER DOWN REFERENCE
SET BUSY HIGH
NO
IS DATA
AVERAGING DONE?
TURN OFF CLOCK
YES
DONE
STORE AUXILIARY INPUT 1 OR 2 IN
AUX1 OR AUX2 REGISTER
Figure 16. Auxiliary Input Flowchart
where:
ΔVBE = difference in diode voltage
N = current ratio of the second measurement to the first
measurement
k = Boltzmann’s constant (1.38 × 10-23 eV/°Kelvin)
q = electron charge (1.60 × 10-19 C)
T = temperature in °Kelvin
The resultant equation solving for °K is:
T(°K) = q x ΔV / (k × ln(N))
AUXILIARY INPUT 1 OR
AUXILIARY INPUT 2
MUX
TEMP1
A/D
CONVERTER
TEMP2
Figure 17. Internal Block Diagram of Temperature Sensor
32
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
NO
HOST WRITES
ADC
CONTROL REGISTER
TEMPERATURE INPUT 1
START CLOCK
START CLOCK
SET BUSY
LOW
SET BUSY
LOW
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
NO
YES
YES
POWER UP REFERENCE
POWER UP
ADC
CONVERT
TEMPERATURE INPUT 1
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
POWER UP REFERENCE
POWER UP
ADC
POWER DOWN
ADC
CONVERT
TEMPERATURE INPUT 1
POWER DOWN REFERENCE
SET BUSY HIGH
NO
IS DATA
AVERAGING DONE?
YES
TEMPERATURE INPUT 1
AND TEMPERATURE INPUT 2
CONVERT
TEMPERATURE INPUT 2
NO
IS DATA
AVERAGING DONE?
YES
STORE TEMPERATURE INPUT 2 IN
TEMP2 REGISTER
POWER DOWN
ADC
POWER DOWN REFERENCE
SET BUSY HIGH
NO
TURN OFF CLOCK
MAX1233/MAX1234
HOST WRITES
ADC
CONTROL REGISTER
IS DATA
AVERAGING DONE?
TURN OFF CLOCK
YES
DONE
STORE TEMPERATURE INPUT 1 IN
TEMP1 REGISTER
DONE
STORE TEMPERATURE INPUT 1 IN
TEMP1 REGISTER
Figure 18. Single Temperature Measurement Process
Figure 19. Differential Temperature Measurement Process
where:
ΔV = V (I N) - V (I1) (in mV)
is 1.6°C/LSB (2.5V reference) and 0.65°C/LSB (1V reference) with a typical accuracy of ±3°C. Figure 19
shows the differential temperature measurementprocess.
T(°K) = 2.68(°K/mV) × ΔV(mV)
T(°C) = [2.68(°K/mV) × ΔV(mV) - 273°K]°C/ °K
This differential conversion method does not require a
test temperature calibration and can provide much
improved absolute temperature measurement. In the
differential conversion method, however, the resolution
Note: The bias current for each diode temperature
measurement is only turned ON during the acquisition
and, therefore, does not noticeably increase power
consumption.
______________________________________________________________________________________
33
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Battery Voltage, Auxiliary Input, and
Temperature Input Scan
Use this scan to make periodic measurements of both
battery inputs, both auxiliary inputs, and both temperature inputs. The respective data registers have the latest results at the end of each cycle. Thus, a single write
by the host to the MAX1233/MAX1234 ADC control register results in six different measurements being made.
Figure 20 shows this scan operation.
Touch-Initiated Screen Scans
(PENSTS = 1; ADSTS = 0)
In the touch-initiated screen-scan mode, the
MAX1233/MAX1234 automatically perform a touchscreen scan upon detecting a screen touch. The touchscreen scans performed are determined by the
[A/D3:A/D0] written to the ADC control register. Figure
21 shows the flowchart for a complete touch-initiated Xand Y- coordinate scan. Selection of resolution, conversion rate, averaging, and touch-screen settling time
determine the overall conversion time.
Figure 22 shows the complete flowchart for a touchinitiated X, Y, and Z scan.
Table 38 shows ADSTS Bit Operation.
Host-Initiated Screen Scans
(PENSTS = ADSTS = 0)
In this mode, the host processor decides when a touchscreen scan begins. The MAX1233/MAX1234 detect a
screen touch and drive PENIRQ LOW. The host recognizes the interrupt request and can choose to write to
the ADC control register to select a touch-screen scan
function (PENSTS = ADSTS = 0). Figures 23 and 24
show the process of a host-initiated screen scan.
Key-Press Initiated Debounce Scan
(KEYSTS1 = 1, KEYSTS0 =0)
In the key-press initiated debounce mode, the
MAX1233/MAX1234 automatically perform a debounce
upon detecting a key press. Key scanning begins once
a key press has been detected and ends when a key
press has been debounced (Figures 25 and 9a).
Host-Initiated Debounce Scan
In this mode, the host processor decides when a
debounce scan begins. The MAX1233/MAX1234 detect
a key press and drive KEYIRQ low. The host processor
recognizes the interrupt request and can choose to
write to the keypad control register to initiate a
debounce scan (Figures 26 and 9b).
Keypad Debouncing
Keys are debounced either when (1) a key press has
been detected, or (2) when commanded by the host MPU.
34
The keys scanned by the keypad row and column pins
are debounced for a period of time (debounce period)
as determined by bits [DBN2:DBN0] of the keypad control register.
The keypad controller continues scanning until the keypad
stays in the same state for an entire debounce period.
Keypad Data
Keypad data can be read out of either the keypad data
status register (maskable), or the keypad data pending
register (not maskable). The keypad mask register is
used to mask individual keys in the keypad data status
register.
GPIO Control
Write to bits [GP7:GP0] of the GPIO control register to
configure one or more of the R_/C_pins as a GPIO pin.
Write to bits [OE7:OE0] of the GPIO control register to
configure the pins as an input or an output. GPIO data
can be read from or written to the GPIO data register. A
read returns the logic state of the GPIO pin. A write sets
the logic state of a GPIO output pin. Writing to a GPIO
input pin has no effect.
GPIO Pullup Disable Register
When programmed as GPIO output, by default, the
GPIO pins are active CMOS outputs. Write a 1 to the
pullup disable register to configure the GPIO output as
an open-drain output.
Using the 8-Bit DAC for LCD/TFT
Contrast Control
Design Example:
The 8-bit DAC offers the ability to control biasing of
LCD/TFT screens. In the circuit of Figure 27, it is
desired to have the MAX1677 DC-DC converter’s VOUT
to be adjustable.
The minimum and maximum DAC voltages (VDAC(HIGH)
and V DAC(LOW) ) can be found in the Electrical
Characteristics table.
The output voltage of the MAX1677 (VOUT) can be calculated by noting the following equations:
VOUT = VREFDAC + i1R1
[Equation 1]
i1 = i2 + i3
[Equation 2]
i2 = VREFDAC / R2
[Equation 3]
[Equation 4]
i3 = (VREFDAC - VDAC) / R3
Substituting equations 2, 3, and 4 into equation 1
yields:
VOUT = VREFDAC + (R1 / R2) VREF + (R1 / R3)
[Equation 5]
(VREFDAC - VDAC)
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
BATTERY VOLTAGE, AUXILIARY INPUT, AND TEMPERATURE INPUT SCAN ([A/D3:A/D0] = 1011)
HOST WRITES
ADC
CONTROL REGISTER
CONVERT
BATTERY INPUT 2
CONVERT
TEMPERATURE INPUT 1
START CLOCK
SET BUSY
LOW
NO
NO
IS DATA
AVERAGING DONE?
NO
YES
IS ADC
REFERENCE IN
AUTO POWER-DOWN
MODE?
STORE BATTERY INPUT 2 IN
BAT2 REGISTER
IS DATA
AVERAGING DONE?
YES
STORE TEMPERATURE INPUT 1 IN
TEMP1 REGISTER
YES
CONVERT
AUXILIARY INPUT 1
POWER UP REFERENCE
POWER UP
ADC
NO
CONVERT
BATTERY INPUT 1
NO
IS DATA
AVERAGING DONE?
YES
IS DATA
AVERAGING DONE?
CONVERT
TEMPERATURE INPUT 2
NO
IS DATA
AVERAGING DONE?
YES
STORE AUXILIARY INPUT 1 IN
AUX1 REGISTER
STORE TEMPERATURE INPUT 2 IN
TEMP2 REGISTER
CONVERT
AUXILIARY INPUT 2
POWER DOWN
ADC
YES
POWER DOWN REFERENCE
STORE BATTERY INPUT 1 IN
BAT1 REGISTER
NO
IS DATA
AVERAGING DONE?
YES
SET BUSY HIGH
TURN OFF CLOCK
DONE
STORE AUXILIARY INPUT 2 IN
AUX2 REGISTER
Figure 20. Scan Mode Flowchart
______________________________________________________________________________________
35
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
PENIRQ-INITIATED
X- AND Y- SCREEN SCAN
SCREEN
TOUCH
YES
POWER DOWN ADC
TURN ON DRIVERS: X+. X-
ARE THERE
UNREAD SCAN
RESULTS?
NO
NO
SET
PENIRQ LOW
IS TOUCH-SCREEN
SETTLING DONE?
YES
IS PENSTS
BIT = 1?
POWER UP ADC
GO TO
NO HOST-INITIATED
SCAN
(FIGURE 23)
CONVERT Y- COORDINATES
YES
START CLOCK
NO
IS DATA
AVERAGING DONE?
SET BUSY LOW
YES
TURN ON DRIVERS: Y+, Y-
NO
IS TOUCH-SCREEN
SETTLING DONE?
STORE Y- COORDINATES IN
Y- REGISTER
POWER DOWN
ADC
SET BUSY HIGH
YES
POWER UP ADC
CONVERT X- COORDINATES
TURN OFF CLOCK
RESET PENIRQ HIGH
DONE
NO
IS DATA
AVERAGING DONE?
YES
STORE X- COORDINATES
IN X- REGISTER
Figure 21. Touch-Initiated X- and Y- Coordinate Screen Scan
36
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
PENIRQ-INITIATED
X, Y, AND Z SCREEN SCAN
SCREEN
TOUCH
STORE X- COORDINATES
IN X- REGISTER
YES
ARE THERE
UNREAD SCAN
RESULTS?
CONVERT Z1- COORDINATES
POWER DOWN ADC
NO
TURN ON DRIVERS: X+, X-
NO
YES
SET
PENIRQ LOW
NO
IS PENSTS
BIT = 1?
IS DATA
AVERAGING DONE?
GO TO
HOST-INITIATED
SCAN
(FIGURE 24)
STORE Z1- COORDINATES
IN Z1- REGISTER
IS TOUCH-SCREEN
SETTLING DONE?
CONVERT Z2 COORDINATES
YES
POWER UP ADC
YES
NO
START CLOCK
IS DATA
AVERAGING DONE?
CONVERT Y- COORDINATES
YES
SET BUSY LOW
NO
IS DATA
AVERAGING DONE?
STORE Z2- COORDINATES
IN Z2- REGISTER
TURN ON DRIVERS: Y+, Y-
YES
NO
POWER UP ADC
STORE Y- COORDINATES IN
Y- REGISTER
IS TOUCH-SCREEN
SETTLING DONE?
SET BUSY HIGH
POWER DOWN ADC
YES
TURN OFF CLOCK
POWER UP ADC
TURN ON DRIVERS: Y+, XRESET PENIRQ HIGH
CONVERT X- COORDINATES
NO
NO
IS DATA
AVERAGING DONE?
IS TOUCH-SCREEN
SETTLING DONE?
DONE
YES
POWER UP ADC
Figure 22. Touch-Initiated X- , Y-, and Z- Coordinate Screen Scan
______________________________________________________________________________________
37
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
HOST-INITIATED
X- AND Y- SCREEN SCAN
SCREEN
TOUCH
STORE X- COORDINATES
IN X- REGISTER
POWER DOWN ADC
YES
ARE THERE
UNREAD SCAN
RESULTS?
TURN ON DRIVERS: X+, XNO
SET
PENIRQ LOW
NO
IS PENSTS
BIT = 1?
YES
GO TO
TOUCH-INITIATED
SCAN
(FIGURE 21)
IS TOUCH-SCREEN
SETTLING DONE?
YES
POWER UP ADC
NO
HOST WRITES
ADC CONTROL REGISTER
(PENSTS = ADSTS = 0)
SET BUSY LOW
START CLOCK
CONVERT Y- COORDINATES
NO
IS DATA
AVERAGING DONE?
YES
STORE Y- COORDINATES IN
Y- REGISTER
TURN ON DRIVERS: Y+, YPOWER DOWN ADC
NO
IS TOUCH-SCREEN
SETTLING DONE?
YES
SET BUSY HIGH
TURN OFF CLOCK
POWER UP ADC
RESET PENIRQ HIGH
CONVERT X- COORDINATES
DONE
NO
IS DATA
AVERAGING DONE?
YES
Figure 23. Host-Initiated X- and Y- Coordinate Screen Scan
38
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
HOST-INITIATED
X-, Y-, AND Z- SCREEN SCAN
TURN ON DRIVERS: Y+, XSCREEN
TOUCH
NO
YES
ARE THERE
UNREAD SCAN
RESULTS?
TURN ON DRIVERS: X+, X-
YES
POWER UP ADC
NO
SET
PENIRQ LOW
IS PENSTS
BIT = 1?
IS TOUCH-SCREEN
SETTLING DONE?
NO
YES
GO TO
TOUCH-INITIATED
SCAN
(FIGURE 22)
IS TOUCH-SCREEN
SETTLING DONE?
CONVERT Z1- COORDINATES
YES
POWER UP ADC
NO
IS DATA
AVERAGING DONE?
NO
HOST WRITES
ADC
CONTROL REGISTER
START CLOCK
YES
CONVERT Y- COORDINATES
STORE Z1- COORDINATES
IN Z1- REGISTER
NO
IS DATA
AVERAGING DONE?
CONVERT Z2- COORDINATES
SET BUSY LOW
YES
TURN ON DRIVERS: Y+, Y-
STORE Y- COORDINATES IN
Y- REGISTER
POWER DOWN ADC
NO
IS TOUCH-SCREEN
SETTLING DONE?
YES
NO
IS DATA
AVERAGING DONE?
YES
STORE Z2- COORDINATES
IIN Z2- REGISTER
POWER DOWN ADC
POWER UP ADC
SET BUSY HIGH
CONVERT X- COORDINATES
TURN OFF CLOCK
NO
IS DATA
AVERAGING DONE?
YES
RESET PENIRQ HIGH
STORE X- COORDINATES
IN X- REGISTER
DONE
POWER DOWN ADC
Figure 24. Host-Initiated X-, Y-, and Z- Coordinate Screen Scan
______________________________________________________________________________________
39
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
HOST-INITIATED DEBOUNCE SCAN
KEY-PRESS-INITIATED DEBOUNCE SCAN
KEYPAD
TOUCH
KEYPAD
TOUCH
YES
YES
ARE THERE
UNREAD DEBOUNCE
RESULTS?
ARE THERE
UNREAD DEBOUNCE
RESULTS?
NO
SET
KEYIRQ LOW
NO
SET
KEYIRQ LOW
IS KEYSTS1 = 1?
IS KEYSTS1 = 1?
NO
GO TO HOST-INITIATED
DEBOUNCE SCAN
YES
YES
GO TO KEY-PRESS-INITIATED
DEBOUNCE SCAN
NO
HOST WRITES
ADC
CONTROL REGISTER
START CLOCK
START CLOCK
SET BUSY LOW
SET BUSY LOW
SCAN AND DEBOUNCE KEYS
SCAN AND DEBOUNCE KEYS
STORE KEYPAD SCAN
RESULTS IN REGISTER
STORE KEYPAD SCAN
RESULTS IN REGISTER
SET BUSY HIGH
SET BUSY HIGH
RESET KEYIRQ HIGH
RESET KEYIRQ HIGH
DONE
DONE
Figure 25. Key-Press-Initiated Debounce Scan
40
Figure 26. Host-Initiated Debounce Scan
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
MAX1233/MAX1234
VBATT
MAX1233
MAX1234
FEEDBACK
RESISTORS
SIMPLIFIED DC/DC CONVERTER
AVDD
DACOUT
R1
i1
R2
i2
ERROR AMP
R3
DAC
i3
CONTROL
VREF
1.25V
VOUT
(LCD BIAS)
MAX1677
Figure 27. LCD Contrast Control Circuit
CS
CS
SCLK
SCK
SCLK
MISO
DOUT
MISO
DOUT
SPI
VDD
CS
CS
SCK
MOSI
DIN
MAX1233
MAX1234
MICROWIRE
MOSI
DIN
BUSY
BUSY
PENIRQ
PENIRQ
KEYIRQ
KEYIRQ
MAX1233
MAX1234
SS
Figure 28a. SPI Interface
Figure 28b. MICROWIRE Interface
Equation 5 shows that the maximum output voltage occurs
for the minimum DAC voltage, and that the minimum
output voltage occurs for the maximum DAC voltage.
To ensure that the desired output swing is achieved,
choose appropriate values of R1, R2, and R3.
Calculate VOUTMIN using the following equation:
VOUTMIN= VREFMIN + (R1MIN / R2MAX)VREFMIN +
(R1MAX / R3MIN) (VREFMIN - VDACMAX)
[Equation 7]
If VOUTMIN is too low for desired operation, avoid the DAC
codes, which cause the output voltage to go too low.
Calculate VOUTMAX using the following equation:
VOUTMAX = VREFMAX + (R1MAX / R2MIN)VREFMAX
+ (R1MAX / R3MIN) (VREFMAX - VDACMIN)
[Equation 6]
If V OUTMAX exceeds the maximum ratings of the
LCD/TFT display, the DAC codes that cause the output
voltage to go too high must be avoided.
Connection to Standard Interface
SPI and MICROWIRE Interfaces
When using an SPI interface (Figure 28a) or
MICROWIRE (Figure 28b), set the CPOL = CPHA = 0.
At least four 8-bit operations are necessary to read or
write data to/from the MAX1233/MAX1234. DOUT data
transitions on the serial clock’s falling edge and is
clocked into the µP on the SCLK’s rising edge. The first
______________________________________________________________________________________
41
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
CS
CS
SCK
SCLK
MISO
DOUT
QSPI
VDD
MOSI
MAX1233
MAX1234
DIN
BUSY
PENIRQ
KEYIRQ
SS
Figure 29. QSPI Interface
SUPPLIES
+3V/+5V
GND
+3V/+5V
R* = 10Ω
AVDD
GND
MAX1233
MAX1234
DVDD
VDD
DGND
DIGITAL
CIRCUITRY
connections. Establish a single-point analog ground
(star ground point) at GND. Connect all analog grounds
to the star ground. Connect the digital system ground
to the star ground at this point only. For lowest noise operation, the ground return to the star ground’s power supply
should be low impedance and as short as possible.
High-frequency noise in the power supply may affect
the high-speed comparator in the ADC. Bypass the
supply to the star ground with a 0.1µF capacitor as
close to pins 1 and 2 of the MAX1233/MAX1234 as
possible. Minimize capacitor lead lengths for best supply-noise rejection. If the power supply is very noisy, a
10Ω resistor can be connected as a lowpass filter.
While using the MAX1233/MAX1234 with a resistive
touch screen, the interconnection between the converter and the touch screen should be as short and robust
as possible. Since resistive touch screens have a low
resistance, longer or loose connections are a source of
error. Noise can also be a major source of error in
touch-screen applications (e.g., applications that
require a backlight LCD panel). This EMI noise can be
coupled through the LCD panel to the touch screen
and cause “flickering” of the converted data. Utilizing a
touch screen with a bottom-side metal layer connected
to ground couples the majority of noise to ground. In
addition, the filter capacitors from Y+, Y-, X+, and Xinputs to ground also help reduce the noise further.
Caution should be observed for settling time of the
touch screen.
Definitions
*OPTIONAL
Figure 30. Power-Supply Grounding Connection
two 8-bit data streams write the command word into the
MAX1233/MAX1234. The next two 8-bit data streams
can contain either the input or output data.
QSPI Interface
Using the high-speed QSPI interface (Figure 29) with
CPOL = 0 and CPHA = 0, the MAX1233/MAX1234 support a maximum fSCLK of 10MHz. DOUT data transitions on the serial clock’s falling edge and is clocked
into the µP on the SCLK’s rising edge.
Layout, Grounding, and Bypassing
For best performance, use printed circuit boards with
good layouts; do not use wire-wrap boards even for
prototyping. Ensure that digital and analog signal lines
are separated from each other. Do not run analog and
digital (especially clock) lines parallel to one another, or
digital lines underneath the ADC package.
Figure 30 shows the recommended system ground
42
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values
on an actual transfer function from a straight line. This
straight line can be either a best-straight-line fit or a line
drawn between the end points of the transfer function,
once offset and gain errors have been nullified. The
static linearity parameters for the MAX1233/MAX1234
are measured using the end-point method.
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1LSB. A
DNL error specification of less than 1LSB guarantees
no missing codes and a monotonic transfer function.
Aperture Jitter
Aperture jitter (tAJ) is the sample-to-sample variation in
the time between the samples.
Aperture Delay
Aperture delay (tAD) is the time defined between the
falling edge of the sampling clock and the instant when
an actual sample is taken.
______________________________________________________________________________________
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the RMS
sum of the first five harmonics of the input signal to the
fundamental itself. This is expressed as:
Signal-to-Noise Plus Distortion
Signal-to-noise plus distortion (SINAD) is the ratio of the
fundamental input frequency’s RMS amplitude to the
RMS equivalent of all other ADC output signals:
SINAD (dB) = 20 ✕ log (SignalRMS / NoiseRMS)
Effective Number of Bits
Effective number of bits (ENOB) indicates the global
accuracy of an ADC at a specific input frequency and
sampling rate. An ideal ADC’s error consists of
quantization noise only. With an input range equal to
the full-scale range of the ADC, calculate the effective
number of bits as follows:
ENOB = (SINAD - 1.76) / 6.02
⎛
V 2 + V32 + V4 2 + V52
THD = 20 × log ⎜ 2
⎜
V12
⎝
⎞
⎟
⎟
⎠
where V1 is the fundamental amplitude, and V2 through
V5 are the amplitudes of the 2nd- through 5th-order
harmonics, respectively.
Spurious-Free Dynamic Range
Spurious-free dynamic range (SFDR) is the ratio of RMS
amplitude of the fundamental (maximum signal component) to the RMS value of the next-largest distortion
component.
Chip Information
TRANSISTOR COUNT: 28,629
Package Information
For the latest package outline information, go to
www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
28 QFN
G2855-2
21-0091
28 TQFN
T2855-6
21-0140
______________________________________________________________________________________
43
MAX1233/MAX1234
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital samples, signal-to-noise ratio (SNR) is the ratio of full-scale
analog input (RMS value) to the RMS quantization error
(residual error). The ideal, theoretical minimum analogto-digital noise is caused by quantization error only and
results directly from the ADC’s resolution (N bits):
SNR = (6.02 ✕ N + 1.76) dB
In reality, there are other noise sources besides quantization noise: thermal noise, reference noise, clock jitter,
etc. SNR is computed by taking the ratio of the RMS
signal to the RMS noise, which includes all spectral
components minus the fundamental, the first five harmonics, and the DC offset.
MAX1233/MAX1234
±15kV ESD-Protected Touch-Screen
Controllers Include DAC and Keypad Controller
Revision History
REVISION
NUMBER
REVISION
DATE
0
7/02
Initial release
4
3/08
Added register address information. Fixed DCLK typo. Fixed CS
timing dependency.
DESCRIPTION
PAGES CHANGED
—
12, 18–27, 29, 41, 42
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.
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is a registered trademark of Maxim Integrated Products.