
P95020 / Preliminary Datasheet
Revision 0.7.10
97
2010 Integrated Device Technology, Inc.
12.1 ADC AND TOUCH SCREEN CONTROLLER ELECTRICAL CHARACTERISTICS
Unless otherwise specified, typical values at TA =25C, VSYS = 3.8V, TA = -40°C to +85°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
VDD
Input Voltage
3
5.5
V
IDD_TSC
Touch Screen Controller
Supply Current
Excluding Sensor Current
3
mA
RES
ADC Resolution
12
bits
DNL
ADC differential non-
linearity
-1
1
LSB
INL
ADC integral non
linearity
-2
2
LSB
Refvol
Internal Reference
Voltage Level Accuracy
Note 1
2.475
2.5
2.525
V
Refacc
Internal Reference
Voltage Accuracy
2
%
Rsw
Sensor Driver Switch
resistance
20
RBAT
VBAT Battery Input
Resistance
Divider End to End Resistance
67.6
BATR
Battery Resistive Divider
Ratio
R1/(R1+R2)
0.5925
EBATR
Battery Resistive Divider
Error
1
%
Notes:
1.
May be subject to the constraints of power supply voltage and battery volt
12.2 ADC AND TOUCH SCREEN CONTROLLER PIN DEFINITIONS
PIN #
PIN_ID
DESCRIPTION
002
ADC1 / GPIO6
ADC1 : X- pin to 4-wire resisitive touch-screen
/ Analog general purpose auxiliary input channel 2
GPIO 6: General Purpose I/O # 6
003
ADC3 / GPIO7
ADC3 : Y- pin to 4-wire resisitive touch-screen
/ Analog general purpose auxiliary input channel 4
GPIO 7: General Purpose I/O # 7
004
ADC2 / GPIO8
ADC2 : Y+ pin to 4-wire resisitive touch-screen
/ Analog general purpose auxiliary input channel 3
GPIO 8: General Purpose I/O # 8
005
ADC0 / GPIO9 /MCLK_IN
ADC0 : X+ pin to 4-wire resisitive touch-screen
/ Analog general purpose auxiliary input channel 1
GPIO 9: General Purpose I/O # 9
MCLK_IN : Master Clock Input
117
ADCGND / GND_BAT
ADCGND & GND_BAT: Shared analog ground pin for ADC and battery charger.
12.3 ADC AND TOUCH SCREEN CONTROLLER OPERATION
The ADC and TSC module comprises of the following functions:
4-wire touch screen controller
General purpose analog signal measurement
On-die temperature and voltage monitoring, including low voltage and high temperature detectors
ADC_TSC_EN and clock generator PLL (0xA034[2:0] default value is 00b, PLL off) need to be enabled if any of the above
mentioned function needs to work. Since the ADC and Reference voltage is powered on only when a measurement is
scheduled, the power consumption will be low if there is no frequent measurements been configured.
The A/D converter is limited to 12-bit resolution, the conversion clock run at 1MHz and conversion takes 12 clock cycles.
The 1MHz clock will be coming from external cystal through PLL.
12.3.1
TOUCH SCREEN MODE
In this mode, pin GPIO6/7/8/9 are supposed to connected to the pin X-/Y-/Y+/X+ of a 4 wire resistive touch screen. The
pen-down detection circuit will be active automatically. When the screen is touched, the pen-down detect it and aserted
PENDOWN signal (mapped to GPIO1) to notify the processor. PENDOWN event could also (if programmed) trigger the
processor interrupt via the interrupt signal (mapped to GPIO5) of the chip. The touch screen controller operates in master
measurement mode. When touched, the controller will automatically initiate the X, Y (and Z1, Z2 if configured)
measurement when the pen-down status is detected. After the convertion is done the result is stored into result registers
and pen-down detection circuit will be back to work. Measurement will restart automatically as long as the pen-down