AD7889 Analog Devices, AD7889 Datasheet - Page 23

• Manufacturer Part Number: AD7889
• Description: Low Voltage Controller for Touch Screens
• Manufacturer: Analog Devices

Specifications of AD7889

• Resolution (bits): 12bit
• # Chan: 6
• Sample Rate: 105kSPS
• Interface: I²C/Ser 2-Wire,Ser,SPI
• Analog Input Type: SE-Uni
• Ain Range: Uni Vdd
• Adc Architecture: SAR
• Pkg Type: CSP

Table 13. Control Register 2
Address
0x02
1
This delay occurs before conversion of the X and Y coordinate channels (including Z1 and Z2) to allow for screen settling and before the first conversion to allow the
ADC to power up.
Bit Name
PM[1:0]
GPIO EN
GPIO DAT
GPIO DIR
GPIO POL
SER/DFR
AVG[1:0]
MED[1:0]
SW/RST
FCD[3:0]
Data Bit
[15:14]
13
12
11
10
9
[8:7]
[6:5]
4
[3:0]
Description
ADC power management.
00 = full shutdown; the ADC, oscillator, bias, and temperature sensor are all powered down.
01 = analog blocks to be powered down depend on the ADC mode.
If ADC mode is master mode, the ADC, oscillator, bias, and temperature sensor are powered
down and must wake up when the user touches the screen.
If ADC mode is slave mode, the ADC and temperature sensor are powered down when not
being used. They wake up automatically when required. The oscillator and bias are powered
up because they are needed to measure time. This also applies to the single-conversion mode.
10 = ADC, bias, and oscillator are powered up continuously, irrespective of ADC mode.
11 = same as 01.
GPIO enable.
0 = AUX/VBAT channel active.
1 = GPIO enabled on AUX/VBAT/GPIO pin.
GPIO data bit.
GPIO direction.
0 = output.
1 = input.
GPIO polarity.
0 = GPIO pin is active low.
1 = GPIO pin is active high.
Selects normal (single-ended) or ratiometric (differential) conversion.
0 = ratiometric (differential).
1 = normal (single-ended).
ADC averaging.
00 = 2 middle values averaged (one measurement when median filter is disabled).
01 = 4 middle values averaged.
10 = 8 middle values averaged.
11 = 16 values averaged.
Median filter size.
00 = median filter disabled.
01 = 4 measurements.
10 = 8 measurements.
11 = 16 measurements.
Software reset; digital logic is reset when this bit is set.
ADC first conversion delay.
Starts at 128 µs (default) and continues to 4.096 ms in steps of 128 µs (see Table 22).
Rev. C | Page 23 of 40
1
AD7879/AD7889
Default
Value
0x4040