AD7877 Analog Devices, AD7877 Datasheet - Page 7

• Manufacturer Part Number: AD7877
• Description: Touch Screen Controller
• Manufacturer: Analog Devices

Specifications of AD7877

• Resolution (bits): 12bit
• # Chan: 9
• Sample Rate: 125kSPS
• Interface: Ser
• Analog Input Type: SE-Uni
• Ain Range: Uni (Vref),Uni 2.5V
• Adc Architecture: SAR
• Pkg Type: CSP

Data Sheet
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
Table 4. Pin Function Descriptions
Pin No.
1, 8, 9, 16,
24, 25, 32
2
3
4
5
6
7
10
11
12
13
14
15
17
18
19
20
21
22
23
26
27
AUX3/GPIO3
AUX2/GPIO2
AUX1/GPIO1
NOTES
1. NC = NO CONNECT
2. THE EXPOSED PAD IS NOT CONNECTED INTERNALLY. FOR
INCREASED RELIABILITY OF THE SOLDER JOINTS AND
MAXIMUM THERMAL CAPABILITY, IT IS RECOMMENDED
THAT THE PAD BE SOLDERED TO GROUND PLANE.
BAT2
BAT1
Mnemonic
NC
BAT2
BAT1
AUX3/GPIO3
AUX2/GPIO2
AUX1/GPIO1
V
X−
Y−
X+
Y+
AGND
DGND
PENIRQ
CS
DIN
STOPACQ
GPIO4
ALERT
DAV
DCLK
DOUT
V
NC
NC
CC
CC
Figure 4. LFCSP Pin Configuration
1
2
3
4
5
6
7
8
32
9
31
10
30
(Not to Scale)
11
AD7877
TOP VIEW
Description
No Connect.
Battery Monitor Input. ADC Input Channel 7.
Battery Monitor Input. ADC Input Channel 6.
Auxiliary Analog Input. ADC Input Channel 5. Can be reconfigured as GPIO pin.
Auxiliary Analog Input. ADC Input Channel 4. Can be reconfigured as GPIO pin.
Auxiliary Analog Input. ADC Input Channel 3. Can be reconfigured as GPIO pin.
Power Supply Input. The V
Touch Screen Position Input.
Touch Screen Position Input. ADC Input Channel 2.
Touch Screen Position Input. ADC Input Channel 0.
Touch Screen Position Input. ADC Input Channel 1.
Analog Ground. Ground reference point for all analog circuitry on the AD7877. All analog input signals and any
external reference signal should be referred to this voltage.
Digital Ground. Ground reference for all digital circuitry on the AD7877. Refer all digital input signals to this
voltage.
Pen Interrupt. Digital active low output (has a 50 kΩ internal pull-up resistor).
Chip Select Input. Active low logic input. This input provides the dual function of initiating conversions on the
AD7877 and enabling the serial input/output register.
SPI® Serial Data Input. Data to be written to the AD7877 registers are provided on this input and clocked into
the register on the rising edge of DCLK.
Stop Acquisition Pin. A signal applied to this pin can be monitored by the AD7877, so that acquisition of new
data by the ADC is halted while the signal is active. Used to reduce the effect of noise from an LCD screen on
the touch screen measurements.
Dedicated General-Purpose Logic Input/Output Pin.
Digital Active Low Output. Interrupt output that goes low if a GPIO data bit is set, or if the AUX1, TEMP1, BAT1,
or BAT2 measurements are out of range.
Data Available Output. Active low logic output. Asserts low when new data is available in the AD7877 results
registers.
External Clock Input. Logic input. DCLK provides the serial clock for accessing data from the part.
Serial Data Output. Logic output. The conversion result from the AD7877 is provided on this output as a serial
data stream. The bits are clocked out on the falling edge of the DCLK input. This output is high impedance
when CS is high.
29
12
28
13
27
14
26
15
25
16
24
23
22
21
20
19
18
17
NC
DAV
ALERT
GPIO4
STOPACQ
DIN
CS
PENIRQ
CC
range for the AD7877 is from 2.2 V to 5.25 V.
Rev. D | Page 7 of 44
Figure 5. WLCSP Pin Configuration
ALERT
DGND
DCLK
STOP
ACQ
PIN 1
CS
PENIRQ
GPIO4
DOUT
DIN
Y+
AD7877 WLCSP
Not to Scale
TOP VIEW
V DRIVE
AUX2/
AGND
GPI02
DAV
X+
ARNG
V REF
BAT1
V CC
Y–
AUX3/
AUX1/
AOUT
GPI03
GPI01
BAT2
X–
AD7877