AD7877 Analog Devices, AD7877 Datasheet - Page 36

• 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

AD7877
Register Name: Control Register 2
Write Address:
Read Address:
Default Value:
Type:
Table 17.
Bit
0
1
2
3
4
5
6
7
8
9
10
11
Name
TMR0
TMR1
REF
POL
FCD0
FCD1
PM0
PM1
ACQ0
ACQ1
AVG0
AVG1
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0010
00010
0x000
Read/write
Description
LSB of conversion interval timer
MSB of conversion interval timer
00 = convert only once
01 = every 1024 clock periods (512 µs)
10 = every 2048 clock periods (1.024 ms)
11 = every 16,384 clock periods (8.19 ms)
Selects internal or external reference
0 = internal reference
1 = external reference
Indicates polarity of signal on STOPACQ pin
0 = active low
1 = active high
LSB of first conversion delay
MSB of first conversion delay
This delay occurs before the first conversion after powering up the ADC, before converting the X and Y
coordinate channels to allow settling, and after the last conversion to allow PENIRQ precharge
00 = 1 clock period delay (500 ns)
01 = 256 clock periods delay (128 µs)
10 = 2048 clock periods delay (1.024 ms)
11 = 16,384 clock periods delay (8.19 ms)
LSB of ADC power management code
MSB of ADC power management code
00 = ADC and reference powered down continuously
For the following codes, regardless of PM bits, the reference is always powered down if the REF bit is 1:
01 = ADC and reference powered down when not converting
10 = ADC and reference powered up continuously (master sequencer does not work if PM = 10)
11 = ADC powered down when not converting, reference powered up
LSB of ADC acquisition time
MSB of ADC acquisition time
00 = 4 clock periods (2 µs)
01 = 8 clock periods (4 µs)
10 = 16 clock periods (8 µs)
11 = 32 clock periods (16 µs)
LSB of ADC averaging code
MSB of ADC averaging code
00 = no averaging (1 conversion per channel)
01 = 4 measurements per channel averaged
10 = 8 measurements per channel averaged
11 = 16 measurements per channel averaged
Rev. D | Page 36 of 44
Data Sheet