WM8199
Production Data
MCLK
VSMP
VS
RS/CL (CDSREF = 00)
RS/CL (CDSREF = 01)
RS/CL (CDSREF = 10)
RS/CL (CDSREF = 11)
Figure 10 Reset Sample and Clamp Timing
For CIS type sensor signals, non-CDS processing is used. In this case, the video level is processed
with respect to the voltage on pin VRLC/VBIAS, generated internally or externally as described
above. The VRLC/VBIAS pin is sampled by Rs at the same time as Vs samples the video level in this
mode.
OFFSET ADJUST AND PROGRAMMABLE GAIN
The output from the CDS block is a differential signal, which is added to the output of an 8-bit Offset
DAC to compensate for offsets and then amplified by an 8-bit PGA. The gain and offset for each
channel are independently programmable by writing to control bits DAC[7:0] and PGA[7:0].
The gain characteristic of the WM8199 PGA is shown in Figure 11. Figure 12 shows the maximum
device input voltage that can be gained up to match the ADC full-scale input range (3V).
8
7
6
5
4
3
2
1
0
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
0
64
128
192
256
0
64
128
192
256
Gain register value (PGA[7:0])
Gain register value (PGA[7:0])
Figure 11 PGA Gain Characteristic
Figure 12 Peak Input Voltage to Match ADC Full-scale Range
In colour line-by-line mode the gain and offset coefficients for each colour can be multiplexed in order
(Red → Green → Blue → Red…) by pulsing the ACYC/RLC pin, or controlled via the FME,
ACYCNRLC and INTM[1:0] bits. Refer to the Line-by-Line Operation section for more details.
ADC INPUT BLACK LEVEL ADJUST
The output from the PGA should be offset to match the full-scale range of the ADC (3V). For
negative-going input video signals, a black level (zero differential) output from the PGA should be
offset to the top of the ADC range by setting register bits PGAFS[1:0]=10. For positive going input
signal the black level should be offset to the bottom of the ADC range by setting PGAFS[1:0]=11.
Bipolar input video is accommodated by setting PGAFS[1:0]=00 or PGAFS[1:0]=01 (zero differential
input voltage gives mid-range ADC output).
PD Rev 3.2 November 2003
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
