WM9713L datasheet(70/111 Pages) WOLFSON

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WM9713L

Preliminary Technical Data

PTD, March 2004, Rev 2.2

TOUCHPANEL SETTLING TIME

For accurate touchpanel measurements, some settling time may be required between the switch

matrix applying a voltage across the touchpanel plate and the ADC sampling the signal. This time

delay function is built into the WM9713L and can be programmed as shown below.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

76h

7:4

DEL

0000

(1 frame)

Touchpanel ADC Settling Time

Table 51 Touchpanel Settling Time Control (1)

DEL

DELAY

(AC-LINK FRAMES)

DELAY

(TIME)

0000

20.8

µs

0001

41.7

µs

0010

83.3

µs

0011

167

µs

0100

333

µs

0101

667

µs

0110

1ms

0111

1.33ms

1000

2ms

1001

128

2.67ms

1010

160

3.33ms

1011

192

4ms

1100

224

4.67ms

1101

256

5.33ms

1110

288

6ms

1111

No delay, switch matrix always on

Table 52 Touchpanel Settling Time Control (2)

The total time for co-ordinate or auxiliary measurements to complete is the delay time DEL, plus one

AC-Link frame (20.8

µs). For a pressure measurement, the time taken is DEL plus two AC-Link

frames (41.6

µs).

Although the DELAY is variable the maximum value that may be programmed depends on the

number of ADCSEL[7:1] bits set, as shown in the following table. Setting multiple ADCSEL[7:1] bits

leaves less spare AC_Link frames for the DELAY.

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