SEMTECH SX8650ICSTRT

SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
4
KEY PRODUCT FEATURES
GENERAL DESCRIPTION
The SX8650 is an ultra low power 4-wire resistive
touchscreen controller optimized for portable equipment
where power and board-space are at a premium.
It incorporates a highly accurate 12-bit ADC for data
conversion and operates from a single 1.65 to 3.7V supply
voltage.
The SX8650 features a built-in preprocessing algorithm for
data measurements, which greatly reduces the host
processing overhead and bus activity. This complete
touchscreen solution includes four user-selectable
operation modes which offer programmability on different
configurations such as conversion rate and settling time,
thus enable optimization in throughput and power
consumption for a wide range of touch sensing applications.
The touch screen inputs have been specially designed to
provide robust on-chip ESD protection of up to ±15kV in
both HBM and Contact Discharge, and eliminates the need
for external protection devices.
The SX8650 supports the Fast-mode I²C (400kbit/s) serial
bus data protocol and includes 2 user-selectable slave
addresses. A custom I2C address is possible on request.
The SX8650 is offered in two tiny packages: a 3.0 mm x
3.0 mm DFN and a 1.5 mm x 2.0 mm wafer-level chip-scale
package (WLCSP).
APPLICATIONS
Extremely Low Power Consumption:[email protected] 8kSPS
Superior On-chip ESD Protection
±15kV HBM (X+,X-,Y+,Y-)
±2kV CDM
±25kV Air Gap Discharge
±15kV Contact Discharge
±300V MM
Single 1.65V to 3.7V Supply/Reference
Integrated Preprocessing Block to Reduce Host Loading
and Bus Activity
Four User Programmable Operation Modes provides
Flexibility to address Different Application Needs
Manual, Automatic, Pen Detect, Pen Trigger
High Precision 12-bit Resolution
Low Noise Ratiometric Conversion
Selectable Polling or Interrupt Modes
Touch Pressure Measurement
400kHz Fast-Mode I²C Interface
Hardware Reset & I²C Software Reset
-40°C to 85°C Operation
12-LD (3.0 mm x 3.0 mm) DFN Package
12 Ball (1.5 mm x 2.0 mm) WLCSP Package
Pb-Free, Halogen Free, RoHS/WEEE compliant product
Windows CE 6.0, Linux Driver Support Available
ORDERING INFORMATION
Portable Equipment
Mobile Communication Devices
Part Number
Cell phone, PDA, MP3, GPS, DSC
Touch Screen Monitors
Block Diagram
Package
SX8650ICSTRT1
12 - Ball WLCSP (1.5 mm x 2.0 mm)
SX8650IWLTRT1
12 - Lead DFN (3.0 mm x 3.0 mm)
1. 3000 Units / reel
SX8650
VDD
AUX
Control
A0
X+
NRST
POR
OSC
I2C
Y+
XYGND
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Touch
Screen
Interface
Vref
SCL
HOST
ref+
in
ADC out
ref-
Page 1
SDA
Digital
Filter
NIRQ
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 2
www.semtech.com
SX8650
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Table of contents
Section
1.
2.
3.
General Description ................................................................................................................................................. 4
1.1.
Pin Diagram DFN............................................................................................................................................. 4
1.2.
Marking Information DFN................................................................................................................................. 4
1.3.
Pin Diagram WLCSP ....................................................................................................................................... 5
1.4.
Marking Information WLCSP ........................................................................................................................... 5
1.5.
Pin Description................................................................................................................................................. 6
1.6.
Simplified Block Diagram ................................................................................................................................. 7
Electrical Characteristics ......................................................................................................................................... 8
2.1.
Absolute Maximum Ratings ............................................................................................................................. 8
2.2.
Recommended Operating Conditions.............................................................................................................. 9
2.3.
Thermal Characteristics ................................................................................................................................... 9
2.4.
Electrical Specifications ................................................................................................................................. 10
2.5.
Host Interface Specifications ......................................................................................................................... 12
2.6.
Host Interface Timing Waveforms.................................................................................................................. 13
2.7.
Typical Operating Characteristics .................................................................................................................. 14
Functional Description ........................................................................................................................................... 16
3.1.
General Introduction ..................................................................................................................................... 16
3.2.
Channel Pins................................................................................................................................................. 17
3.2.1.
X+, X-, Y+. Y- .......................................................................................................................................... 17
3.2.2.
AUX ......................................................................................................................................................... 17
3.3.
Host Interface and Control Pins ..................................................................................................................... 18
3.3.1.
NIRQ ....................................................................................................................................................... 18
3.3.2.
SCL ......................................................................................................................................................... 18
3.3.3.
SDA ......................................................................................................................................................... 18
3.3.4.
A0 ............................................................................................................................................................ 19
3.3.5.
NRST ...................................................................................................................................................... 19
3.4.
4.
Page
Power Management Pins............................................................................................................................... 20
3.4.1.
VDD......................................................................................................................................................... 20
3.4.2.
GND ........................................................................................................................................................ 20
Detailed Description............................................................................................................................................... 21
4.1.
Touch Screen Operation................................................................................................................................ 21
4.2.
Coordinates Measurement............................................................................................................................. 22
4.3.
Pressure Measurement.................................................................................................................................. 23
4.4.
Pen Detection ................................................................................................................................................ 25
4.5.
Data Processing............................................................................................................................................. 26
4.6.
Host Interface and Control ............................................................................................................................. 28
4.6.1.
I2C Address ............................................................................................................................................ 28
4.6.2.
I2C Write Registers ................................................................................................................................. 29
4.6.3.
I2C Read Registers ................................................................................................................................. 30
4.6.4.
I2C Host Commands ............................................................................................................................... 31
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 2
www.semtech.com
SX8650
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
Table of contents
Section
Page
4.6.5.
I2C Read Channels ................................................................................................................................ 32
4.6.6.
Data Channel Format ............................................................................................................................. 33
4.6.7.
Invalid Qualified Data .............................................................................................................................. 33
4.7.
I2C Register Map .......................................................................................................................................... 34
4.8.
Host Control Writing....................................................................................................................................... 35
4.9.
Host Commands ............................................................................................................................................ 37
4.10. Power-Up ....................................................................................................................................................... 38
4.11. Reset.............................................................................................................................................................. 38
5.
Modes of Operation .............................................................................................................................................. 39
5.1.
6.
7.
Manual Mode ................................................................................................................................................. 39
5.1.1.
CONVERT Command ............................................................................................................................. 39
5.1.2.
SELECT Command................................................................................................................................. 40
5.2.
Automatic mode ............................................................................................................................................. 41
5.3.
PENDET Mode .............................................................................................................................................. 42
5.4.
PENTRIG Mode ............................................................................................................................................. 42
Application Information .......................................................................................................................................... 44
6.1.
Acquisition Setup ........................................................................................................................................... 44
6.2.
Channel Selection.......................................................................................................................................... 44
6.3.
Noise Reduction............................................................................................................................................. 44
6.3.1.
POWDLY................................................................................................................................................. 44
6.3.2.
SETDLY .................................................................................................................................................. 44
6.3.3.
AUX Input ................................................................................................................................................ 45
6.4.
Channel Biasing............................................................................................................................................. 45
6.5.
Interrupt Generation....................................................................................................................................... 45
6.6.
Coordinate Throughput Rate ......................................................................................................................... 46
6.6.1.
I2C Communication Time........................................................................................................................ 46
6.6.2.
Conversion Time ..................................................................................................................................... 46
6.7.
Application Schematic.................................................................................................................................... 48
6.8.
Application Examples..................................................................................................................................... 49
6.8.1.
Soft Keyboard ......................................................................................................................................... 49
6.8.2.
Game ...................................................................................................................................................... 49
6.8.3.
Handwriting Application........................................................................................................................... 50
6.8.4.
Slider Controls......................................................................................................................................... 50
Packaging Information ........................................................................................................................................... 51
7.1.
Package Outline Drawing .............................................................................................................................. 51
7.1.1.
DFN Package .......................................................................................................................................... 51
7.1.2.
WLCSP Package .................................................................................................................................... 52
7.2.
Land Pattern Drawing .................................................................................................................................... 53
7.2.1.
DFN Land Pattern ................................................................................................................................... 53
7.2.2.
WLCSP Land Pattern .............................................................................................................................. 54
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 3
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
1. General Description
1.1. Pin Diagram DFN
VDD
1
X+
2
Y+
3
SX8650
TOP VIEW
12
AUX
11
A0
10
NRST
13
X-
4
9
SCL
Y-
5
8
SDA
GND
6
7
NIRQ
Figure 1. Pinout diagram, DFN
1.2. Marking Information DFN
8650
YYWW
XXXX
PIN 1
IDENTIFIER
Figure 2. Marking information, DFN
On Figure 2, YYWW is the Date Code and XXXX is the Lot Number.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 4
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
1.3. Pin Diagram WLCSP
SX8650 TOP VIEW
solder bumps on bottom side
X+
Y+
X-
Y-
VDD
A0
NRST
GND
AUX
NIRQ
SDA
SCL
C
D
3
2
1
A
B
Figure 3. Pinout diagram, WLCSP
1.4. Marking Information WLCSP
8650
Eyww
BALL A1
IDENTIFIER
Figure 4. Marking information, WLCSP
On Figure 4, YYWW is the Date Code and XXXXX is the Lot Number.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 5
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
1.5. Pin Description
Pin Number #
Name
Type
Description
DFN
WLCSP
1
A2
VDD
Power
Input power supply connect to a 0.1uF capacitor to GND
2
A3
X+
Analog
X+ channel input
3
B3
Y+
Analog
Y+ channel input
4
C3
X-
Analog
X- channel input
5
D3
Y-
Analog
Y- channel input
6
D2
GND
Ground
Ground
7
B1
NIRQ
Digital Output / Open Drain Output
Interrupt output, active low. Need external pull-up resistor
8
C1
SDA
Digital Input / Open Drain Output
I2C data input/output
9
D1
SCL
Digital Input / Open Drain Output
I2C clock, input/output
10
C2
NRST
Digital Input / Output
Reset Input, active low. Need external 50k pull-up resistor
11
B2
A0
Digital Input
I2C slave address selection input
12
A1
AUX
Digital Input/Analog Input
Analog auxiliary input or conversion synchronization
GND
Ground
Die attach paddle, connect to Ground
13
Table 1. Pin description
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 6
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
1.6. Simplified Block Diagram
The SX8650 simplified block diagram is shown in Figure 5.
SX8650
VDD
AUX
Control
X+
A0
Y+
NRST
POR
X-
Y-
Touch
Screen
Interface
GND
Vref
OSC
I2C
SCL
ref+
in
ADC out
ref-
SDA
Digital
Filter
NIRQ
Figure 5. Simplified block diagram of the SX8650
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 7
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
2. Electrical Characteristics
2.1. Absolute Maximum Ratings
Stresses above the values listed in “Absolute Maximum Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of the device at these, or any other conditions beyond the “Recommended Operating
Conditions”, is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Parameter
Symbol
Min.
Max.
Unit
Supply Voltage
VDDABS
-0.5
3.9
V
Input voltage (non-supply pins)
VIN
-0.5
3.9
V
Input current (non-supply pins)
IIN
10
mA
Operating Junction Temperature
TJCT
125
°C
Reflow temperature
TRE
260
°C
Storage temperature
TSTOR
150
°C
High ESD pins: X+, X-,Y+,Y-
± 15(i)
kV
± 8(ii)
kV
ESDHBM2
± 2(ii)
kV
ESDCD
± 15
kV
ILU
± 100(iii)
mA
ESDHBM1
ESD HBM
(Human Body Model)
All pins except high ESD pins:
AUX,A0,NRST,NIRQ,SDA,SCL
ESD (Contact Discharge)
High ESD pins: X+, X-,Y+,Y-
Latchup
-50
Table 2. Absolute Maximum Ratings
(i)
(ii)
(iii)
Tested to TLP (10A)
Tested to JEDEC standard JESD22-A114
Tested to JEDEC standard JESD78
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 8
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
2.2. Recommended Operating Conditions
Parameter
Supply Voltage
Ambient Temperature Range
Symbol
Min.
Max
Unit
VDD
1.65V
3.7
V
TA
-40
85
°C
Min.
Max
Unit
Table 3. Recommended Operating Conditions
2.3. Thermal Characteristics
Symbol
Parameter
Thermal Resistance with DFN package - Junction to Ambient (i)
θJA
39
°C/W
Thermal Resistance with WLCSP package - Junction to Ambient (i)
θJA
65
°C/W
Table 4. Thermal Characteristics
θJA is calculated from a package in still air, mounted to 3" x 4.5", 4 layer FR4 PCB with thermal vias under exposed pad (if
applicable) per JESD51 standards.
(i)
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 9
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
2.4. Electrical Specifications
All values are valid within the recommended operating conditions unless otherwise specified.
Parameter
Symbol
Conditions
Min.
Typ
Max
Unit
Current consumption
Manual
Ipwd
Manual (converter stopped, pen
detection off, I2C listening, OSC
stopped)
0.4
0.75
uA
Pen Detect
Ipndt
Pen detect mode (converter
stopped, pen detection activated,
device will generate interrupt upon
detection, I2C listening, OSC
stopped).
0.4
0.75
uA
Pen Trigger
Ipntr
Pen trigger mode (converter
stopped, pen detection activated,
device will start conversion upon
pen detection. I2C listening, OSC
stopped
0.4
0.75
uA
Automatic
Iwt
Automatic (converter stopped, pen
detection off, I2C listening, OSC and
timer on, device is waiting for timer
expiry)
1.5
Operation @8kSPS, VDD=1.8V
Iopl
X,Y Conv. RATE=4kSPS, Nfilt=1
PowDly=0.5us, SetDly=0.5us
23
50
uA
Operation @42kSPS, VDD=3.3V Ioph
X,Y Conv. RATE=3kSPS, Nfilt=7
PowDly=0.5us, SetDly=0.5us
105
140
uA
uA
Digital I/O
High-level input voltage
VIH
0.7VDD
VDD+0.5
V
Low-level input voltage
VIL
VSS-0.3
0.3VDD
V
SDA / SCL Hysteresis of Schmitt Vhys
trigger inputs
VDD > 2 V
VDD < 2 V
Low-level output voltage
Input leakage current
VOL
LI
0.05VDD
0.1VDD
IOL=3mA, VDD>2V
IOL=3mA, VDD<2V
0
0
CMOS input
V
0.4
0.2VDD
V
±1
uA
VDD
V
AUX
Input voltage range
VIAUX
0
Table 5. Electrical Specifications
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 10
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
Parameter
Input capacitance
Input leakage current
Symbol
Conditions
Min.
Typ
Max
Unit
CX+,CX-,CY+,
CY-
50
pF
CAUX
5
pF
IIAUX
-1
1
uA
1
ms
Startup
Power-up time
tpor
Time between rising edge VDD and
rising NIRQ
ADC
Resolution
Ares
Offset
Aoff
Gain error
Age
Differential nonlinearity
Integral nonlinearity
12
bits
±1
LSB
0.5
LSB
Adnl
±1
LSB
Ainl
±1.5
LSB
5
Ohm
At full scale
Resistors
X+, X-, Y+, Y- resistance
Rchn
Touch Pad Biasing Resistance
Pen detect resistance
RPNDT_00
RPNDT = 0
100
kOhm
RPNDT_01
RPNDT = 1
200
kOhm
RPNDT_10
RPNDT = 2
50
kOhm
RPNDT_11
RPNDT = 3
25
kOhm
0.1
uF
External components
Capacitor between VDD, GND
recommendations
Cvdd
Type 0402, tolerance +/-50%
Table 5. Electrical Specifications
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 11
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
2.5. Host Interface Specifications
Parameter
Symbol
Condition
Min
Typ
Max
Unit
400
kHz
I2C TIMING SPECIFICATIONS (i)
SCL clock frequency
fSCL
0
SCL low period
tLOW
1.3
us
SCL high period
tHIGH
0.6
us
Data setup time
tSU;DAT
100
ns
Data hold time
tHD;DAT
0
ns
Repeated start setup time
tSU;STA
0.6
us
Start condition hold time
tHD;STA
0.6
us
Stop condition setup time
tSU;STO
0.6
us
Bus free time between stop and start
tBUF
1.3
us
Data valid time
tVD;DAT
0.9
us
Data valid ack time
tVD;ACK
0.9
us
Pulse width of spikes that must be
suppressed by the input filter
tSP
50
ns
Capacitive Load on each bus line SCL, SDA Cb
400
pF
I2C BUS SPECIFICATIONS
Table 6. Host Interface Specifications
Notes:
(i)
All timing specifications refer to voltage levels (VIL, VIH, VOL) defined in Table 5 unless otherwise mentioned.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 12
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
2.6. Host Interface Timing Waveforms
SDA
70%
30%
70%
SCL
tSU;STA
tHD;STA
tSU;STO
tBUF
Figure 6. I2C Start and Stop timing
SDA
70%
30%
SCL
70%
30%
tLOW
tHIGH
tHD;DAT
tSU;DAT
tSP
Figure 7. I2C Data timing
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 13
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
2.7. Typical Operating Characteristics
At Ta= -40°C to +85°C, VDD=1.7V to 3.7V, PowDly=0.5 us, SetDly=0.5us, Filt=1, Resistive touch screen sensor current not
taking in account, unless otherwise noted.
SUPPLY CURRENT in MANUAL MODE
vs TEMPERATURE
CURRENT IN PEN TRIGGER MODE
500
700
V DD=3.3V
Manual Mode Supply Current (nA)
TOUCH SENSOR
NOT ACTIVATED
Supply Current (nA)
400
300
200
100
600
VDD=1.85V
500
400
300
200
100
0
0
1.5
2
2.5
3
-40
3.5
-20
0
40
60
80
100
SUPPLY CURRENT VS CONVERSION RATE
VDD=1.8V - X,Y, Z1, Z2 CONVERSION
SUPPLY CURRENT VS CONVERSION RATE
VDD=1.8V - X,Y CONVERSION
130
100
90
120
Filt=7
Supply Current (uA)
Filt=5
70
60
50
Filt=3
40
30
Filt=5
110
100
80
Supply Current (uA)
20
Temperature (C)
V DD (V)
Filt=1
90
Filt=3
80
70
60
50
Filt=1
40
20
30
20
10
10
0
Filt=7
0
0
1
2
3
4
0
5
Conversion Rate (kCPS)
1
2
3
4
5
Conversion Rate (kCPS)
SUPPLY CURRENT vs SAMPLE RATE
500
TOUCH SENSOR
X+ to X- =1000 Ohm
Y+ to Y- =1000 Ohm
400
V DD=3.3V
Supply Current (uA)
V DD=2.5V
300
V DD=1.65V
200
100
0
0
1
2
3
4
5
Sample Rate (kCPS)
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 14
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
Typical Operating Characteristics (continued)
At Ta= -40°C to +85°C, VDD=1.7V to 3.7V, PowDly=0.5 us, SetDly=0.5us, Filt=1, Resistive touch screen sensor current not
taking in account, unless otherwise noted.
CHANGE IN ADC OFFSET vs. TEMPERATURE
2
2
1
1
Delta from +25C (LSB)
Delta from +25C (LSB)
CHANGE IN ADC GAIN vs. TEMPERATURE
0
-1
-2
-40
-20
0
20
40
60
80
0
-1
-2
-40
100
Temperature (C)
-20
0
20
40
60
80
100
Temperature (C)
ADC INL @ VDD=3.3V
1
0.75
Error (LSB)
0.5
0.25
0
-0.25
-0.5
-0.75
-1
0
0.5
1
1.5
2
2.5
3
VX+(V)
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 15
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
3. Functional Description
3.1. General Introduction
This section provides an overview of the SX8650 architecture, device pinout and a typical application.
The SX8650 is designed for 4-wire resistive touch screen applications (Figure 8).The touch screen or touch panel is the
resistive sensor and can be activated by either a finger or stylus. The touch screen coordinates and touch pressure are
converted into I2C format by the SX8650 for transfer to the host.
SX8650
VDD
AUX
Control
A0
NRST
X+
POR
OSC
I2C
Y+
XYGND
Touch
Screen
Interface
Vref
SCL
HOST
ref+
in
ADC out
ref-
SDA
Digital
Filter
NIRQ
Figure 8. SX8650 with screen
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 16
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
3.2. Channel Pins
3.2.1. X+, X-, Y+. Y-
The SX8650's channel pins (X+, X-, Y+, Y-) directly connect to standard touch screen X and Y resistive layers. The
SX8650 separately biases each of these layers and converts the resistive values into (X,Y) coordinates.
The channel pins are protected to VDD and GROUND.
Figure 9 shows the simplified diagram of the X+, X-, Y+, Y- pins.
VDD
X+
XY+
Y-
Touch Screen
Interface
Rchn
Figure 9. Simplified diagram of X+, X-, Y+, Y- pins
3.2.2. AUX
The SX8650 interface includes an AUX pin that serves two functions: an ADC input; and a start of conversion trigger. When
used as an ADC, the single ended input range is from GND to VDD, referred to GND. When the AUX input is configured to
start conversions, the AUX input can be further configured as a rising and / or falling edge trigger.
The AUX is protected to VDD and GROUND.
Figure 10 shows a simplified diagram of the AUX pin.
VDD
ADC
AUX
Control
Figure 10. Simplified diagram of AUX
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 17
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
3.3. Host Interface and Control Pins
The SX8650 host and control interface consists of: NIRQ, I2C pins SCL and SDA, A0, and NRST.
3.3.1. NIRQ
The NIRQ pin is an active low, open drain output to facilitate interfacing to different supply voltages and thus requires an
external pull-up resistor (1-10 kOhm). The NIRQ pin does not have protection to VDD.
The NIRQ function is designed to provide an interrupt to the host processor. Interrupts may occur when a pen is detected,
or when channel data is available.
Figure 11 shows a simplified diagram of the NIRQ pin.
HOST
VDD
IRQ
Control
NIRQ
Figure 11. Simplified diagram of NIRQ
3.3.2. SCL
The SCL pin is a high-impedance input and open-drain output pin. The SCL pin does not have protection to VDD to
conform to I2C slave specifications. An external pull-up resistor (1-10 kOhm) is required.
Figure 12 shows the simplified diagram of the SCL pin.
HOST
VDD
SCL
IN
SCL
I2C
OUT
Figure 12. Simplified diagram of SCL
3.3.3. SDA
SDA is an I/O pin. It can be used as an open-drain output (with external pull-up resistor) or as an input. An external pull-up
resistor (1-10 kOhm) is required.
The SDA I/O pin does not have protection to VDD to conform to I2C slave specifications.
Figure 13 shows a simplified diagram of the SDA pin.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 18
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
HOST
VDD
SDA
I2C
IN
SDA
OUT
Figure 13. Simplified diagram of SDA
3.3.4. A0
The A0 pin is connected to the I2C address select control circuitry and is used to modify the device I2C address.
The A0 pin is protected to GROUND.
Figure 14 shows a simplified diagram of the A0 pin.
I2C
A0
Figure 14. Simplified diagram of A0
3.3.5. NRST
The NRST pin is an active low input that provides a hardware reset of the SX8650's control circuitry.
The NRST pin is protected GROUND to enable interfacing with devices at a different supply voltages.
Figure 15 shows a simplified diagram of the NRST pin.
HOST
VDD
Control
NRST
Figure 15. Simplified diagram of NRST
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 19
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
3.4. Power Management Pins
The SX8650's power management input consists of the following Power and Ground pins.
3.4.1. VDD
The VDD is a power pin and is the power supply for the SX8650.
The VDD has ESD protection to GROUND.
Figure 16 shows a simplified diagram of the VDD pin.
VDD
VDD
Figure 16. Simplified diagram of VDD
3.4.2. GND
The SX8650 has one power management ground pin, GND1.
The GND has ESD protection to VDD.
Figure 17 shows a simplified diagram of the GND pin.
VDD
GND
Figure 17. Simplified diagram of GND
1.
The die attach paddle on DFN is also connected to GND
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 20
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4. Detailed Description
4.1. Touch Screen Operation
A resistive touch screen consists of two (resistive) conductive sheets separated by an insulator when not pressed. Each
sheet is connected through 2 electrodes at the border of the sheet (Figure 18). When a pressure is applied on the top
sheet, a connection with the lower sheet is established. Figure 19 shows how the Y coordinate can be measured. The
electrode plates are connected through terminals X+, X- and Y+, Y- to an analog to digital converter (ADC) and a reference
voltage. The resistance between the terminals X+ and X- is defined by Rxtot. Rxtot will be split in 2 resistors, R1 and R2, in
case the screen is touched. The resistance between the terminals Y+ and Y- is represented by R3 and R4. The connection
between the top and bottom sheet is represented by the touch resistance (RT).
Y+
top conductive sheet
electrodes
Y-
electrodes
X+
X-
bottom conductive sheet
Figure 18. Touch Screen
Y+
R3
+
Vref
-
X-
RT
R2
R1 X+
+
-
ADC
Ypos
R4
YFigure 19. Touch Screen Operation ordinate measurement (Y)
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 21
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.2. Coordinates Measurement
The top resistive sheet (Y) is biased with a voltage source. Resistors R3 and R4 determine a voltage divider proportional to
the Y position of the contact point. Since the converter has a high input impedance, no current flows through R1 so that the
voltage X+ at the converter input is given by the voltage divider created by R3 and R4.
The X coordinate is measured in a similar fashion with the bottom resistive sheet (X) biased to create a voltage divider by
R1 and R2, while the voltage on the top sheet is measured through R3. Figure 20 shows the coordinates measurement
setup. The resistance RT is the resistance obtained when a pressure is applied on the screen. RT is created by the contact
area of the X and Y resistive sheet and varies with the applied pressure.
Ypos
X+
Y+
R1
X+
R3
RT
R2
X-
Y+
R1
+
Vref
-
+
Vref
-
R4
Y-
Xpos
R3
RT
R2
X-
R4
Y-
Figure 20. Ordinate (Y) and abscissa (X) coordinates measurement setup
The X and Y position are found by:
R2
Xpos = 4095 ⋅ -------------------R1 + R2
R4
Ypos = 4095 ⋅ -------------------R3 + R4
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 22
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.3. Pressure Measurement
The pressure measurement consists of two additional setups: z1 and z2 (see Figure 21).
X+
R1
+
Vref
-
z1
Y+
X+
R1
R3
+
Vref
-
RT
R2
Y+
R3
RT
R2
R4
R4
z2
X-
Y-
X-
Y-
Figure 21. z1 and z2 pressure measurement setup
The corresponding equations for the pressure:
R4
z1 = 4095 ⋅ --------------------------------R1 + R4 + R T
R4 + Rt
z2 = 4095 ⋅ --------------------------------R1 + R4 + R T
The X and Y total sheet resistance (Rxtot, Rytot) are known from the touch screen supplier.
Rxtot = R1 + R2
Rytot = R3 + R4
R4 is proportional to the Y coordinate. The R4 value is given by the total Y plate resistance multiplied by the fraction of the
Y position over the full coordinate range.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 23
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
Ypos
R4 = Rytot ⋅ -----------4095
By re-arranging z1 and z2 one obtains
z2
R T = R4 ⋅ ----- – 1
z1
Which results in:
Ypos
R T = Rytot ⋅ ------------ ⋅
4095
z2
----- – 1
z1
The touch resistance calculation above requires three channel measurements (Ypos, z2 and z1) and one specification data
(Rytot).
An alternative calculation method is using Xpos, Ypos, one z channel and both Rxtot and Rytot shown in the next
calculations.
R1 is inverse proportional to the X coordinate.
Xpos
R1 = Rxtot ⋅ 1 – ------------4095
Substituting R1 and R4 into z1 and rearranging terms gives:
Rytot ⋅ Y pos 4095
Xpos
R T = ------------------------------- ⋅ ------------ – 1 – Rxtot ⋅ 1 – ------------4095
z1
4095
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 24
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.4. Pen Detection
If the touchscreen is powered between X+ and Y- through a resistor RPNDT, no current will flow so long as pressure is not
applied to the surface (see Figure 22). Node X+ will remain at the voltage reference voltage. When some pressure is
applied, a current path is created and brings X+ to the level defined by the resistive divider determined by RPNDT and the
sum of R1, RT and R4.
The X+ level is detected by a comparator followed by a S-R latch. RPNDT should be set to a value greater than 7x(Rxtot +
Rytot).
The pen detection will set the PENIRQ bit of the I2C status register and will activate (LOW) the NIRQ pin of the SX8650.
The PENIRQ bit will be cleared and the NIRQ will be de-asserted as soon as the host reads the I2C status register.
RPNDT
Y+
X+
S
+
Vref
-
Y-
R3
RT
R1
R4
R2
Q
RNIRQ
Q
NIRQ
X-
Figure 22. Pen detection
The resistor RPNDT can be configured to 4 different values (see Table 9) to accommodate different screen resistive values.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 25
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.5. Data Processing
The SX8650 offers 4 types of data processing which allows the user to make trade-offs between data throughput, power
consumption and noise rejection.
The parameter FILT is used to select the filter order Nfilt as seen in Figure 7. The noise rejection will be improved with a
high order to the detriment of the power consumption. The effective coordinate throughput will remain the same for all filter
configurations as the ADC will be enabled more often. For very high coordinate throughput rates the filter needs to be set
to FILT=0 (see Table 7).
FILT
Nfilt
0
1
1
3
2
5
3
7
Table 7. Filter order
Figure 23 shows the SX8650 configuration (FILT = 0) in which the ADC output samples, sn are sent directly to the I2C
interface. The FILT parameter can be setup through the I2C registers
.
ADC
sn,sn-1,sn-2,....
=
cn,cn-1,cn-2,....
I2C
Figure 23. data processing, FILT = 0
In the case of FILT=1 three output samples of the ADC are averaged and the result is sent to the I2C.
sn,sn-1,sn-2
ADC
1 2
⋅ ∑ sn − i
3 i =0
cn
I2C
Figure 24. data processing, FILT = 1
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 26
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
For FILT=2 the averaging is done on five samples
.
sn,sn-1,....,sn-4
1 4
⋅ ∑ sn − i
5 i =0
ADC
cn
I2C
Figure 25. data processing, FILT = 2
The FILT=3 will re-arrange seven samples out of the ADC in an ascending order and average the three center samples.
Figure 26 shows an example of the ordering and averaging.
.
sort
max
sn,sn-1,....,sn-6
ADC
sn
sn-3
sn-2 = an-2
sn-4 = an-1
sn-5 = an
sn-1
sn-6
1 2
⋅ ∑ an − i
3 i=0
cn
I2C
min
Figure 26. data processing, FILT = 3
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 27
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.6. Host Interface and Control
The host interface consists of I2C (SCL and SDA) and the NIRQ, A0, NRST signals.
The I2C implemented on the SX8650 is compliant with:
- Standard Mode (100 kbit/s) & Fast Mode (400 kbit/s)
- Slave mode
- 7 bit slave address
4.6.1. I2C Address
Pin A0 defines the LSB of the I2C address. It is shown on Figure 27.
.
1 0 0 1 0 0 0
with pin A0 connected to ground
1 0 0 1 0 0 1
with pin A0 connected to VDD
SX8650 Slave Address(7:1) =
Figure 27. I2C slave address
Upon request of the customer, a custom I2C address can be burned in the NVM.
The host uses the I2C to read and write data and commands to the configuration and status registers. During a conversion,
the I2C clock can be stretched until the end of the processing.
Channel data read is done by I2C throughput optimized formats.
The supported I2C access formats are described in the next sections:
- I2C Write Registers
- I2C Read Registers
- I2C Host Commands
- I2C Read Channels
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 28
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.6.2. I2C Write Registers
The format for I2C write is given in Figure 28.
After the start condition [S], the SX8650 slave address (SA) is sent, followed by an eighth bit (W=‘0’) indicating a Write.
The SX8650 then Acknowledges [A] that it is being addressed, and the host sends 8-bit Command and Register address
consisting of the command bits ‘000’ followed by the SX8650 Register Address (RA).
The SX8650 Acknowledges [A] and the host sends the appropriate 8-bit Data Byte (WD0) to be written.
Again the SX8650 Acknowledges [A].
In case the host needs to write more data, a succeeding 8-bit Data Byte will follow (WD1), acknowledged by the slave [A].
This sequence will be repeated until the host terminates the transfer with the Stop condition [P].
S
SA
W A
CR
A
WD0
A
A
Optional
Clock stretching
S:
SA:
W:
A:
CR:
WDn:
P:
WD1
Start condition
SX8650 Slave Address(7:1)
'0'
Acknowledge
'000' + Register Address(4:0)
Write Data byte(7:0), 0...n
Stop condition
WDn
A
P
Optional
From host to SX8650
From SX8650 to host
Figure 28. I2C write register
The register address increments automatically when successive register data (WD1...WDn) is supplied by the host. This
automatic increment can be used for the first 4 register addresses (see Table 8).
The correct sampling of the screen by the SX8650 and the host I2C bus traffic are events that might occur simultaneously.
The SX8650 will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly
after the last received command bit (see Figure 28).
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 29
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.6.3. I2C Read Registers
The format for incremental I2C read for registers is given in Figure 29. The read has to start with a write of the read
address.
After the start condition [S], the SX8650 Slave Address (SA) is sent, followed by an eighth bit (W=‘0’) indicating a Write.
The SX8650 then Acknowledges [A] that it is being addressed, and the host responds with a 8-bit CR Data consisting of
‘010’ followed by the Register Address (RA). The SX8650 responds with an Acknowledge [A] and the host sends the
Repeated Start Condition [Sr]. Once again, the SX8650 Slave Address (SA) is sent, followed by an eighth bit (R=‘1’)
indicating a Read.
The SX8650 responds with an Acknowledge [A] and the read Data byte (RD0). If the host needs to read more data it will
acknowledge [A] and the SX8650 will send the next read byte (RD1). This sequence can be repeated until the host
terminates with a NACK [N] followed by a stop [P].
S
SA
W
A
CR
A
Sr
SA
R
A
RD0
A
RD1
A
RDn
N
P
Optional
S:
Sr:
SA:
W:
R:
A:
N:
CR:
RDn:
P:
Start Condition
Repeated Start Condition
SX8650 Slave Address(7:1)
'0'
'1'
ACKnowledge
Not ACKnowledge (terminating read stream)
'010' + Register Address(4:0)
Read Data byte(7:0), 0...n
Stop Condition
From Host to SX8650
From SX8650 to Host
Figure 29. I2C read registers
The I2C read register format of Figure 29 is maintained until the Stop Condition. After the Stop Condition the SX8650 is
performing succeeding reads by the compact read format of the I2C read channels described in the next section.
No clock stretching will occur for the I2C read registers.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 30
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.6.4. I2C Host Commands
The format for I2C commands is given in Figure 30.
After the start condition [S], the SX8650 Slave Address (SA) is sent, followed by an eighth bit (W=‘0’) indicating a Write.
The SX8650 then Acknowledges [A] that it is being addressed, and the host responds with an 8-bit Data consisting of a ‘1’
+ command(6:0). The SX8650 Acknowledges [A] and the host sends a stop [P].
The exact definition of command(6:0) can be found in section [4.9]
S
SA
W A
CR
A
P
Clock stretching
S:
SA:
W:
A:
CR:
P:
Start condition
SX8650 Slave Address(7:1)
'0'
Acknowledge
'1' + Command(6:0)
Stop condition
From host to SX8650
From SX8650 to host
Figure 30. I2C host command
The sampling of the screen by the SX8650 and the host I2C bus traffic are events that might occur simultaneously. The
SX8650 will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly after
the last received command bit (see Figure 30).
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 31
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.6.5. I2C Read Channels
The host is able to read the channels with a high throughput, by the format shown in Figure 31.
After the start condition [S], the SX8650 Slave Address (SA) is sent, followed by an eighth bit (R=‘1’) indicating a read. The
SX8650 responds with an Acknowledge [A] and the Read Data byte (RD0). The host sends an Acknowledge [A] and the
SX8650 responds with the Read Data byte (RD1). If the host needs to read more data, it will acknowledge [A] and the
SX8650 will send the next read bytes. This sequence can be repeated until the host terminates with a NACK [N] followed
by a stop [P].
The channel data that can be read is defined by the last conversion sequence.
A maximum number of 10 data bytes is passed when all channels (X, Y, z1, z2 and AUX) are activated in the
“I2CRegChanMsk”.
The channel data is sent with the following order: X, Y, Z1, Z2, AUX. The first byte of the data contains the channel
information as shown in Figure 32.
Typical applications require only X and Y coordinates, thus only 4 bytes of data will be read.
S
SA
R
A
RD0
A
RD1
A RDn-1 A
Channel (i)
Clock stretching
S:
SA:
R:
A:
N:
RDn:
P:
Start condition
SX8650 Slave Address(7:1)
'1'
Acknowledge
Not Acknowledge (terminating read stream)
Read Data byte(7:0), 0...n
Stop condition
RDn
N
P
Channel (i+1)
From host to SX8650
From SX8650 to host
Figure 31. I2C read channels
The sampling of the screen by the SX8650 and the host I2C bus traffic are events that might occur simultaneously. The
SX8650 will synchronize these events by the use of clock stretching if that is required. The stretching occurs directly after
the address and read bit have been sent for the I2C read channels command (see Figure 31).
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 32
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.6.6. Data Channel Format
Channel data is coded on 16 bits as shown in Figure 32
0
C H A N (2:0)
D (7:0)
D (11:8)
RD1
RD0
Figure 32. data channel format
The 3 bits CHAN(2:0) are defined in Table 12 and show which channel data is referenced. The channel data D(11:0) is of
unsigned format and corresponds to a value between 0 and 4095.
4.6.7. Invalid Qualified Data
The SX8650 will return 0xFFFF data in case of invalid qualified data.
This occurs:
- when the SX8650 converted channels and the host channel readings do not correspond. E.g. the host converts X and Y
and the host tries to read X, Y and z1 and z2.
- when a conversion is done without a pen being detected.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 33
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.7. I2C Register Map
I2C register address RA(4:0)
Register
Description
0 0000
I2CRegCtrl0
Write, Read
0 0001
I2CRegCtrl1
Write, Read
0 0010
I2CRegCtrl2
Write, Read
0 0100
I2CRegChanMsk
Write, Read
0 0101
I2CRegStat
Read
1 1111
I2CRegSoftReset
Write
Table 8. I2C Register address
The details of the registers are described in the next sections.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 34
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.8. Host Control Writing
The host control writing allows the host to change SX8650 settings. The control data goes from the host towards the
SX8650 and may be read back for verification.
register
bits
default
description
Set rate in coordinates per sec (cps) (± 20%)
If RATE equals zero then Manual mode.
if RATE is larger than zero then Automatic mode
7:4
0000
0000: Timer disabled -Manual mode
0001: 10 cps
0010: 20 cps
0011: 40 cps
0100: 60 cps
0101: 80 cps
0110: 100 cps
0111: 200 cps
RATE
I2CRegCtrl0
1000: 300 cps
1001: 400 cps
1010: 500 cps
1011: 1k cps
1100: 2k cps
1101: 3k cps
1110: 4k cps
1111: 5k cps
Settling time (± 10%): The channel will be biased for a time of POWDLY
before each channel conversion
3:0
7:6
0000
00
POWDLY
0000: Immediate (0.5 us)
0001: 1.1 us
0010: 2.2 us
0011: 4.4 us
0100: 8.9 us
0101: 17.8 us
0110: 35.5 us
0111: 71.0 us
1000: 0.14 ms
1001: 0.28 ms
1010: 0.57 ms
1011: 1.14 ms
1100: 2.27 ms
1101: 4.55 ms
1110: 9.09 ms
1111: 18.19 ms
00: AUX is used as an analog input
01: On rising AUX edge, wait
POWDLY and start acquisition
10: On falling AUX edge, wait
POWDLY and start acquisition
11: On rising and falling AUX
edges, wait POWDLY and start
acquisition
AUXAQC
The AUX trigger requires the manual mode.
I2CRegCtrl1
5
1
CONDIRQ
4
0
reserved
3:2
1:0
00
00
Enable conditional interrupts
0: interrupt always generated at end of conversion cycle. If no pen is
detected the data is set to ‘invalid qualified’.
1: interrupt generated when pen detect is successful
RPDNT
Select the Pen Detect Resistor
00: 100 KOhm
01: 200 KOhm
10: 50 KOhm
11: 25 KOhm
FILT
Digital filter control
00: Disable
01: 3 sample averaging
10: 5 sample averaging
11: 7 sample acquisition, sort, average 3 middle samples
Table 9. I2C registers
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 35
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
register
bits
default
7:4
0
description
reserved
Settling time while filtering (± 10%)
When filtering is enabled, the channel will initially bias for a time of
POWDLY for the first conversion, and for a time of SETDLY for each
subsequent conversion in a filter set.
0000: Immediate (0.5 us)
0001: 1.1 us
0010: 2.2 us
0011: 4.4 us
0100: 8.9 us
0101: 17.8 us
0110: 35.5 us
0111: 71.0 us
I2CRegCtrl2
I2CRegChanMsk
3:0
0000
SETDLY
7
1
XCONV
0: no sample
1: sample, report X channel
6
1
YCONV
0: no sample
1: sample, report Y channel
5
0
Z1CONV
0: no sample
1: sample, report Z1 channel
4
0
Z2CONV
0: no sample
1:sample, report Z2 channel
3
0
AUXCONV
0: no sample
1: sample, report AUX channel
0
0
reserved
0
0
reserved
0
0
reserved
1000: 0.14 ms
1001: 0.28 ms
1010: 0.57 ms
1011: 1.14 ms
1100: 2.27 ms
1101: 4.55 ms
1110: 9.09 ms
1111: 18.19 ms
The host status reading allows the host to read the status of the SX8650. The data goes from the SX8650
towards the host. Host writing to this register is ignored.
I2CRegStat
7
0
CONVIRQ
0: no IRQ pending
1: End of conversion sequence IRQ pending
IRQ is cleared by the I2C channel reading
6
0
PENIRQ
operational in pen detect mode
0: no IRQ pending
1: Pen detected IRQ pending
IRQ is cleared by the I2C status reading
5:0
I2CRegSoftReset
000000 reserved
7:0
0x00
If the host writes the value 0xDE to this register, then the SX8650 will be reset.
Any other data will not affect the SX8650
Table 9. I2C registers
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 36
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.9. Host Commands
The host can write to and read from registers of the SX8650 by the write and read commands as defined in Table 10.
W/R command name
CR(7:0)
4
Function
7
6
5
3
2
1
0
WRITE(RA)
0
0
0
RA(4:0)
Write register (see Table 8 for RA)
READ(RA)
0
1
0
RA(4:0)
Read register (see Table 8 for RA)
Table 10. I2C W/R commands
.The host can issue commands to change the operation mode or perform manual actions as defined in Table 11.
command name
CR(7:0)
Function
7
6
5
4
3
2
1
0
SELECT(CHAN)
1
0
0
0
x
CHAN(2:0)
Bias channel (see Table 12 for CHAN)
CONVERT(CHAN)
1
0
0
1
x
CHAN(2:0)
Bias channel (see Table 12 for CHAN)
Wait POWDLY settling time
Run conversion
MANAUTO
1
0
1
1
x
x
x
x
Enter manual or automatic mode.
PENDET
1
1
0
0
x
x
x
x
Enter pen detect mode.
PENTRG
1
1
1
0
x
x
x
x
Enter pen trigger mode.
Table 11. I2C commands
The channels are defined as in Table 12.
Channel
CHAN(2:0)
Function
2
1
0
X
0
0
0
X channel
Y
0
0
1
Y channel
Z1
0
1
0
First channel for pressure measurement
Z2
0
1
1
Second channel for pressure measurement
AUX
1
0
0
Auxiliary channel
reserved
1
0
1
reserved
1
1
0
SEQ
1
1
1
Channel sequentially selected from
I2CRegChanMsk register, (see Table 8)
Table 12. channel definition
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 37
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
4.10. Power-Up
The NIRQ pin is kept low during SX8650 power-up.
During power-up, the SX8650 is not accessible and I2C communications are ignored.
As soon as NIRQ rises, the SX8650 is ready for I2C communication.
voltage
VDD
VDD/2
time
t POR
voltage
NIRQ
time
Figure 33.
Power-up, NIRQ
4.11. Reset
The POR of the SX8650 will reset all registers and states of the SX8650 at power-up.
Additionally the host can reset the SX8650 by asserting the NRST pin (active low) and via the I2C bus.
If NRST is driven LOW, then NIRQ will be driven low by the SX8650. When NRST is released (or set to high) then NIRQ
will be released by the SX8650.
The circuit has also a soft reset capability. When writing the code 0xDE to the register I2CRegSoftReset, the circuit will be
reset.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 38
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
5. Modes of Operation
The SX8650 has four operation modes that are configured using the I2C commands as defined in Table 11 and Table 9.
These 4 modes are:
- manual (command ‘MANAUTO’ and RATE=0),
- automatic (command ‘MANAUTO’ and RATE>0),
- pen detect (command ‘PENDET’),
- pen trigger mode (command ‘PENTRG’).
At startup the SX8650 is set in manual mode.
In the manual mode the SX8650 is entirely stopped except for the I2C peripheral which accepts host commands. This
mode requires RATE equal to be zero (RATE = 0, see Table 9).
In the automatic mode the SX8650 will sequence automatic channel conversions. This mode requires RATE to be larger
than zero (RATE > 0, see Table 9).
In the PENDET mode the pen detection is activated. The SX8650 will generate an interrupt (NIRQ) upon pen detection and
set the PENIRQ bit in the I2C status register. To quit the PENDET mode the host needs to configure the manual mode.
In the PENTRG mode the pen detection is activated and a channel conversion will start after the detection of a pen. The
SX8650 will generate an interrupt (NIRQ) upon pen detection and set the CONVIRQ bit in the I2C status register. To quit
the PENTRIG mode the host needs to configure the manual mode. The PENTRG mode offers the best compromise
between power consumption and coordinate throughput.
5.1. Manual Mode
In manual mode (RATE=0) single actions are triggered by I2C commands. When a command is received, the SX8650
executes the associated task and waits for the next command. It is up to the host to sequence all actions such as: select an
input channel, wait for a settling time, start conversion and read the result. The commands used in manual mode are
typically SELECT and/or CONVERT as defined in Table 10. The CONVERT command should only be used with
CONDIRQ=0.
If the SX8650 is not ready to execute the next command, clock starching occurs. Various timing diagrams show the
operating sequence for examples of the manual mode.
The I2C and the NIRQ are describing the host interface signals. The ‘bias’, ‘sample’ and ‘convert channel(s)’ used on the
following drawings are internal SX8650 signals and shown for illustration only.
5.1.1. CONVERT Command
The CONVERT command will bias the selected channel, wait the time specified by POWDLY and then convert the selected
channel. The converted channel can be one single channel or channels in sequence depending on the CHAN(2:0)
parameter. The reading of the channel(s) can be done over the I2C as described in Figure 31.
An example host I2C sequence for acquisition of the x channel using the CONVERT command is shown in Figure 34 and
Figure 35. The settling time is determined by POWDLY
The init setup could be a I2C write sequence of:
I2CregCtrl1=0x00 // No filter, CONDIRQ = 0
I2CRegChanMsk = 0x80 // Acquisition of the X channel
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 39
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
I2C
init setup
CONVERT
channel
read x position
Read x
POWDLY
settling time
bias channel
sample channel
convert channel
Figure 34. Conversion of a channel, no filter
I2C
init setup
CONVERT
channel
read x position (I2C clock stretched)
POWDLY
settling time
I2C clock stretching
Read x
bias channel
sample channel
convert channel
Figure 35. Conversion of a channel, digital filter enabled, clock starching required
5.1.2. SELECT Command
The host can define very long settling times by using the SELECT, CONVERT sequence. The host determines the settling
time for each separate channel by the time interval between issuing the SELECT and CONVERT command. Therefore the
POWDLY timing is not applicable and is ignored.
As soon as the channel is selected the corresponding channel will be biased. The settling time is determined by the interval
between the host issuing the SELECT and the CONVERT commands. The host can proceed with a read channel
command after the CONVERT command. In case the SX8650 is not ready to convert and filter, the clock of the I2C will be
stretched by the SX8650 until data is available and can be read.
Figure 36 shows an example of I2C sequence using the SELECT, CONVERT sequence command. For an X-channel
SELECT, issue the command: 0x80, followed with the corresponding CONVERT command: 0x90. The SX8650 will make
the X-channel data available over the I2C.
I2C
init setup
SELECT
channel
CONVERT
channel
read x position
Read x
Host determined
settling time
bias channel
sample channel
convert channel
Figure 36. Conversion using the SELECT and CONVERT command
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 40
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
init setup
I2C
SELECT
channel
CONVERT
channel
read x position
NIRQ
bias channel
sample channel
convert channel
Figure 37.
single conversion, filtering and interrupt signaling
In Figure 37 the host performs a single conversion and uses the interrupt (NIRQ) signal to read the available data. The
clock stretching is not required and the I2C bus is free for other system traffic. Successive reads require the same diagram
The init setup could be a I2C write sequence of:
I2CRegCtrl1 = 0x23 // Interrupt enable, seven samples filtering
I2CRegChanMsk = XCONV // Acquisition of X
5.2. Automatic mode
In automatic mode (RATE > 0) the SX8650 will automatically decide when to start acquisition, sequence all the acquisitions
and alerts the host if data is available for download with a NIRQ. The host will read the channels and the SX8650 will start
again with the next conversion cycle.
The fastest coordinate rate is obtained if the host reads the channels immediately after the NIRQ.
If the host reads faster than the NIRQ rate, I2C clock stretching occurs or invalid qualified data will be returned, see section
[4.6.7]
To not loose data, the SX8650 will not begin conversion before the host read the channels. If after the NIRQ a delay
superior to the sampling period is made by the host to read the channels a slower coordinate rate is obtained.
The interrupts will be always generated if the control CONDIRQ bit (see Table 9) is cleared to ‘0’. In case there is no pen
detected on the screen then the coordinate data will be qualified as invalid, see section [4.6.7]. This result in a regular
interrupt stream, as long as the host performs the read channel commands, independent of the screen being touched or
not.
If the control CONVIRQ bit (see register I2CregStat Table 9) is set to ‘1’ then the interrupts will only be generated if the pen
detect occurred. This result in a regular interrupt stream, as long as the host performs the read channel commands, only
when the screen is touched. When the screen is not touched, interrupts does not occur.
Figure 38 and Figure 39 show the automatic-sequential mode. After the first sample I2C to make the initialization, traffic is
reduced as only I2C reads are required.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 41
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
I2C
read x, y
position
init setup
NIRQ
X
bias channel
Y
POWDLY
POWDLY
sample channel
convert channel
SETDLY SETDLY
SETDLY SETDLY
Figure 38. auto mode, sequential 2-channel conversion, 3 sample filtering and interrupt signaling, first
conversion
Figure 38 shows the very first conversion of 2 channels. Figure 39 shows the subsequent conversions.
I2CRegCtrl0=0xB8 //1 kCPS RATE, 140us POWDLY
I2CRegCtrl1=0x21 // Interrupt enable, three samples filtering
I2CRegChanMsk=0xC0
read x, y
position
I2C
NIRQ
bias channel
x
y
RATE
x
sample channel
convert channel
Figure 39.
auto mode, sequential 2-channel conversion, 3 sample filtering and interrupt signaling, subsequent
conversions
All succeeding conversions notifies the host by an interrupt signal and the host only needs to issue the I2C read command.
The reads occur at the RATE interval.
5.3. PENDET Mode
The PENDET mode can be used if the host only needs to know if the screen has been touched or not and take from that
information further actions. When pen detect circuitry is triggered the interrupt signal NIRQ will be generated and the status
register bit ‘PENIRQ’ will be set. The bit is cleared by reading the status register I2CRegStat.
5.4. PENTRIG Mode
The PENTRIG mode offers the best compromise between power consumption and coordinate throughput.
In this mode the SX8650 will wait until a pen is detected on the screen and then starts the coordinate conversions. The
host will be signalled only when the screen is touched and coordinates are available.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 42
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
The coordinate rate in pen trigger mode is determined by the speed of the host reading the channels and the conversion
times of the channels. The host performs the minimum number of I2C commands in this mode.
Figure 40 shows the PENTRIG mode. In this example, the host waits for the NIRQ interrupt to make the acquisition of the
x,y data. After the first sample, I2C control traffic is reduced as only I2C reads are required.
Pen detected
I2C
init setup
read x, y
position
read x, y
position
NIRQ
x,y
Conversion time
Figure 40.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
x,y
Conversion time
Pen trigger mode
Page 43
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
6. Application Information
This section describes in more detail application oriented data.
6.1. Acquisition Setup
Prior to an acquisition, the SX8650 can be setup by writing the control registers. Registers are written by issuing the
register write command. They can be read by issuing the read command. Please refer to the section [4.8].
If no registers are written, the circuit will start in manual mode.
6.2. Channel Selection
The SX8650 can be setup to start a single channel conversion or to convert several channels in sequence. For a single
conversion, the channel to be converted is determined from the CHAN(2:0) field in the command word (defined in
Table 12).
Several channels can be acquired sequentially by setting the CHAN(2:0) field to SEQ. The channels will be sampled in the
order defined by register I2CRegChanMsk from MSB to LSB.
If a “one” is written in a channel mask, the corresponding channel will be sampled, in the opposite case, it is ignored and
the next selected channel is chosen.
6.3. Noise Reduction
A noisy environment can decrease the performance of the controller. For example, an LCD display located just under the
touch screen can adds a lot of noise on the high impedance A/D converter inputs.
6.3.1. POWDLY
Adding a capacitor from the touch screen drivers to ground is a solution to minimize external noise. A low-pass filter
created by the capacitor may increase settling time. Therefore, use POWDLY to stretch the acquisition period. POWDLY
can be estimated by the following formula.
PowDly = 10 × Rtouch × Ctouch
Rtouch is the sum of the panel resistances plus any significant series input resistance, Rxtot + Rytot + Ri.
Ctouch is the sum of the touch panel capacitance plus any noise filtering and routing capacitances.
6.3.2. SETDLY
A second method of noise filtering uses an averaging filter as described in section [4.5] (Data processing). In this case, the
chip will sequence up to 7 conversions on each channel. The parameter SETDLY sets the settling time between the
consecutive conversions (shown in Figure 41).
In most applications, SETDLY can be set to 0. In some particular applications, where accuracy of 1LSB is required and
Ctouch is less than 100nF a specific value should be determined.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 44
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
X+
Start of the
conversion
5 successive
conversions
POWDLY
SETDLY
time
Figure 41. POWDLY and SETDLY timing with FILT=2
6.3.3. AUX Input
An alternate conversion trigger method can be used if the host system provides additional digital signals that indicate noisy
or noise-free periods. The SX8650 can be set up to start conversions triggered by the AUX pin. A rising edge, a falling
edge or both can trigger the conversion. To enter this mode, AUXACQ must be set to a different value than '00' as defined
in Table 9. The AUX edge will first trigger the bias delay (POWDLY). Following the programmed delay, the channel
acquisition takes place.
6.4. Channel Biasing
The touch screen surface presents a resistive and capacitive load, and therefore the screen bias needs to settle before an
acquisition takes place. In the manual mode, the channels selected are biased when either a SELECT or CONVERT
command is received.
The channel can be biased for an arbitrary amount of time by first sending a SELECT command and then a CONVERT
command once the settling time requirement is met.
The SELECT command can be omitted if the large range of POWDLY settings cover the requirements. In the latter case,
the CONVERT command alone is enough to perform an acquisition.
In the sequential mode, multiple channels are sampled. This requires programming the POWDLY field in register
I2CRegCTRL0. The selected channel will be powered during POWDLY before a conversion is started. The channel bias is
automatically removed after the conversion has completed.
6.5. Interrupt Generation
An interrupt (NIRQ) will be generated:
- during the power-up phase
- after completion of a conversion. CONVIRQ (bit [7] of I2CRegStat) will be set at the same time.
- when a pen detect is triggered, the SX8650 being in pen detect mode. PENIRQ (bit [6] of I2CRegStat) will be set at the
same time.
The NIRQ will be released and then pulled high by the external pull-up resistor:
- when the power-up phase is finished
- the host reading all channels that were previously converted by the SX8650. CONVIRQ, will be cleared at the same time.
- the host reading the I2C status register, the SX8650 being in pen detect mode. PENIRQ, will be cleared at the same time.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 45
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
An active NIRQ (low) needs to be cleared before any new conversions will occur.
6.6. Coordinate Throughput Rate
When the chip is not set to Automatic mode, the coordinate throughput rate depends on the following factors:
- the I2C communication time
- the conversion time
If the SX8650 is set to Automatic mode then the RATE settling must not be faster than the Raw Conversion Rate (RCR).
RCR ( kCPS ) = 1000 ⁄ T conv ( us )
6.6.1. I2C Communication Time
The time to read the channel data by I2C depends of the mode set and if the clock is stretched or not.
Mode
Clock Stretching
Tcomm(us)
MANUAL
No
TSU;STA -TLOW + (29+18*Nchan)*TSCL
MANUAL
Yes
-TLOW + (21+18*Nchan)*TSCL
PENTRIG1
No
TSU;STA -TLOW + (9+18*Nchan)*TSCL
PENTRIG1
Yes
-TLOW + (1+18*Nchan)*TSCL
Table 13.
1. With the pen always down
The highest throughput will be obtained with a I2C frequency of 400kHz and clock stretching when all channels are
sampled in PENTRIG mode.
The host should react to the NIRQ interrupt signal as quickly as possible by reading the channel data.
6.6.2. Conversion Time
The maximum possible throughput can be estimated with the following equation
Tconv ( us ) = 47 ⋅ Tosc + N chan ⋅ ( POWDLY + ( N filt – 1 ) ⋅ SETDLY + ( 21N filt + 1 ) ⋅ Tosc )
with:
- Nfilt = {1,3,5,7} based on the order defined for the filter FILT (see Figure 7).
- Nchan = {1,2,3,4,5} based on the number of channels defined in I2CRegChanMsk
- POWDLY = 0.5us to 18.19ms, settling time as defined in I2CRegCtrl0
- SETDLY = 0.5us to 18.19ms, settling time when filtering as defined in I2CRegCtrl2
- Tosc is the oscillator period (555ns +/- 15%)
The Coordinate Rate (CR) and Equivalent Coordinate Rate (ECR) which give the number of coordinates (X, Y, Z1, Z2) is
given below
:
CR ( kCPS ) = 1000 ⁄ T ( us )
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 46
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
ECR ( kCPS ) = N chan ⋅ CR
The Sample Rate (SR) and Equivalent Sample Rate (ESR) which give the number of sample per second (X, Y, Z1, Z2) is
given below
SR ( kSPS ) = N filt ⋅ CR
ESR ( kSPS ) = N chan ⋅ N filt ⋅ CR
Table 14 gives some examples of Coordinate Rate and Sample Rate for various setting in PENTRIG mode.
Nch
[1..5]
Nfilt
[1 3 5 7]
PowDly
[uS]
SetDly
[uS]
Tconv
[uS]
Tcomm
[uS]
2.0
1.0
0.5
0.5
51.7
91.2
2.0
1.0
2.2
0.5
55.0
2.0
1.0
8.9
0.5
2.0
1.0
35.5
2.0
1.0
2.0
Total
[uS]
CR
[kCPS]
ECR
[kCPS]
SR
[kSPS]
ESR
[kSPS]
142.9
7.0
14.0
7.0
14.0
91.2
146.2
6.8
13.7
6.8
13.7
68.3
91.2
159.5
6.3
12.5
6.3
12.5
0.5
121.7
91.2
212.9
4.7
9.4
4.7
9.4
280.0
0.5
619.4
91.2
710.6
1.4
2.8
1.4
2.8
3.0
2.2
0.5
103.9
91.2
195.1
5.1
10.3
15.4
30.8
2.0
3.0
35.5
0.5
170.6
91.2
261.8
3.8
7.6
11.5
22.9
2.0
5.0
2.2
0.5
152.8
91.2
244.0
4.1
8.2
20.5
41.0
2.0
5.0
35.5
0.5
219.4
91.2
310.6
3.2
6.4
16.1
32.2
4.0
7.0
2.2
0.5
377.2
181.2
558.4
1.8
7.2
12.5
50.1
4.0
7.0
35.5
0.5
510.6
181.2
691.8
1.4
5.8
10.1
40.5
4.0
1.0
0.5
0.5
77.2
181.2
258.4
3.9
15.5
3.9
15.5
4.0
1.0
2.2
0.5
83.9
181.2
265.1
3.8
15.1
3.8
15.1
4.0
1.0
35.5
0.5
217.2
181.2
398.4
2.5
10.0
2.5
10.0
4.0
3.0
2.2
0.5
181.7
181.2
362.9
2.8
11.0
8.3
33.1
4.0
3.0
35.5
0.5
315.0
181.2
496.2
2.0
8.1
6.0
24.2
4.0
5.0
2.2
0.5
279.4
181.2
460.6
2.2
8.7
10.9
43.4
4.0
5.0
35.5
0.5
412.8
181.2
594.0
1.7
6.7
8.4
33.7
4.0
7.0
2.2
0.5
377.2
181.2
558.4
1.8
7.2
12.5
50.1
4.0
7.0
35.5
0.5
510.6
181.2
691.8
1.4
5.8
10.1
40.5
Table 14. Coordinate throughput examples
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 47
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
6.7. Application Schematic
A typical application schematic is shown in Figure 42
SX8650
VDD
AUX
Control
A0
X+
NRST
POR
OSC
I2C
Y+
XYGND
Touch
Screen
Interface
Vref
Figure 42.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
SCL
HOST
ref+
in
ADC out
ref-
SDA
Digital
Filter
NIRQ
typical application
Page 48
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
6.8. Application Examples
6.8.1. Soft Keyboard
Figure 43. Keyboard
A keyboard application can be designed with the help of the SX8650. The data are entered by tapping keys on the
keyboard with a stylus. The SX8650 send the key coordinates to the microcontroller which interpret them as a symbol.
When the keyboard is not activated, the chip stays in low power mode to save power.
6.8.2. Game
Figure 44. Game
Many kinds of game can be designed with touchscreen. With its high data throughput and its ability to sense pressure,
SX8650 is the perfect controller for this kind of application.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 49
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
6.8.3. Handwriting Application
Figure 45. Handwriting application
An handwriting application needs a powerful microcontroller to run recognition algorithms. The SX8650 includes a
preprocessing block to reduce host activity.
6.8.4. Slider Controls
Figure 46. Slider controls
Every kind of controls such as rotative knob, slider, button could be emulated with a SX8650 associated to a touchscreen.
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 50
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
7. Packaging Information
7.1. Package Outline Drawing
7.1.1. DFN Package
The 12-Lead DFN (3mm x 3mm) package is shown in Figure 47
D
A
B
DIM
A
A1
A2
b
D
D1
E
E1
e
L
N
aaa
bbb
E
PIN 1
INDICATOR
(LASER MARK)
A
DIMENSIONS
INCHES
MILLIMETERS
MIN NOM MAX MIN NOM MAX
.028
.000
.030 .031
.001 .002
(.008)
.006 .008 .010
.114 .118 .122
.074 .079 .083
.114 .118 .122
.042 .048 .052
.018 BSC
.012 .016 .020
12
.003
.004
0.70
0.00
0.75 0.80
0.02 0.05
(0.20)
0.15 0.20 0.25
2.90 3.00 3.10
1.87 2.02 2.12
2.90 3.00 3.10
1.06 1.21 1.31
0.45 BSC
0.30 0.40 0.50
12
0.08
0.10
SEATING
PLANE
aaa C
C
A1
A2
D1
1
2
e/2
LxN
E/2
E1
N
e
bxN
D/2
bbb
C A B
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS TERMINALS.
Figure 47. DFN Package outline drawing
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 51
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
7.1.2. WLCSP Package
The WLCSP-W12 package as shown in Figure 48
A
B
1.5±0.10
INDEX AREA
A1 CORNER
2.0±0.10
0.10 C
0.25±0.10
C
0.625 Max.
1.00
SEATING
PLANE
0.08 C
0.50
D
0.50
C
1.50
B
0.25
A
1
2
3
12X Ø.30±0.05
0.05
C A B
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS
Figure 48. WLCSP Package outline drawing
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 52
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
7.2. Land Pattern Drawing
7.2.1. DFN Land Pattern
The land pattern of 12-Lead DFN (3mm x 3mm) is shown in Figure 49.
K
DIM
(C)
Z
G
H
Y
X
P
C
G
H
K
P
X
Y
Z
DIMENSIONS
INCHES
MILLIMETERS
(.112)
.075
.055
.087
.018
.010
.037
.150
(2.85)
1.90
1.40
2.20
0.45
0.25
0.95
3.80
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2.
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
3. THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD
SHALL BE CONNECTED TO A SYSTEM GROUND PLANE.
FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR
FUNCTIONAL PERFORMANCE OF THE DEVICE.
Figure 49. DFN Land Pattern
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 53
www.semtech.com
SX8650
World’s Lowest Power & Smallest Footprint 4-wire
Resistive Touchscreen Controller with 15kV ESD
DATASHEET
ADVANCED COMMUNICATIONS & SENSING
7.2.2. WLCSP Land Pattern
The land pattern of WLCSP is shown on Figure 50
1.00
0.50
0.50
0.25
1.50
12X Ø0.325
NOTES:
1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS
2. THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
Figure 50. WLCSP Land Pattern
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 54
www.semtech.com
SX8650
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
© Semtech 2008
All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The
information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable
and may be changed without notice. No liability will be accepted by the publisher for any consequence of its use. Publication
thereof does not convey nor imply any license under patent or other industrial or intellectual property rights. Semtech assumes
no responsibility or liability whatsoever for any failure or unexpected operation resulting from misuse, neglect improper
installation, repair or improper handling or unusual physical or electrical stress including, but not limited to, exposure to
parameters beyond the specified maximum ratings or operation outside the specified range.
SEMTECH PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN
LIFE-SUPPORT APPLICATIONS, DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF
SEMTECH PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE UNDERTAKEN SOLELY AT THE CUSTOMER’S
OWN RISK. Should a customer purchase or use Semtech products for any such unauthorized application, the customer shall
indemnify and hold Semtech and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims,
costs damages and attorney fees which could arise.
Contact information
Semtech Corporation Advanced Communications & Sensing Products
E-mail: [email protected]@semtech.comInternet: http://www.semtech.com
USA
200 Flynn Road, Camarillo, CA 93012-8790.
Tel: +1 805 498 2111 Fax: +1 805 498 3804
FAR EAST
12F, No. 89 Sec. 5, Nanking E. Road, Taipei, 105, TWN, R.O.C.
Tel: +886 2 2748 3380 Fax: +886 2 2748 3390
EUROPE
Semtech Ltd., Units 2 & 3, Park Court, Premier Way, Abbey Park Industrial Estate, Romsey, Hampshire, SO51 9DN.
Tel: +44 (0)1794 527 600 Fax: +44 (0)1794 527 601
ISO9001
CERTIFIED
ACS Revision V2.15/October 2009
©2009 Semtech Corp.
Page 55
www.semtech.com