wm8150scds-r Wolfson Microelectronics plc, wm8150scds-r Datasheet - Page 12

• Manufacturer Part Number: wm8150scds-r
• Description: Single Channel 12-bit Cis/ccd Afe With 4-bit Wide Output
• Manufacturer: Wolfson Microelectronics plc

WM8150
OFFSET ADJUST AND PROGRAMMABLE GAIN
w
Figure 7 PGA Gain Characteristic
9
8
7
6
5
4
3
2
1
0
0
GAIN REGISTER VALUE, PGA[7:0]
64
Figure 6 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 R
mode; non-CDS processing is achieved by setting switch 2 in the lower position, CDS = 0.
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 can be set
for each of three colours by writing to control bits DACx[7:0] and PGAx[7:0] (where x can be R, G or
B).
In colour line-by-line mode the gain and offset coefficients that are applied to the PGA and offset
DAC can be multiplexed by control of the INTM[1:0] bits as shown in Table 1.
Table 1 Offset DAC and PGA Register Control
The gain characteristic of the WM8150 PGA is shown in Figure 7. Figure 8 shows the maximum
input voltage (at VINP) that can be gained up to match the ADC full-scale input range (2.5V).
INTM[1:0]
128
R
R
R
R
S
S
S
S
00
01
10
11
/CL (CDSREF = 00)
/CL (CDSREF = 01)
/CL (CDSREF = 10)
/CL (CDSREF = 11)
192
Red offset and gain registers are applied to offset DAC and PGA
(DACR[7:0] and PGAR[7:0])
Green offset and gain registers applied to offset DAC and PGA
(DACG[7:0] and PGAG[7:0])
Blue offset and gain registers applied to offset DAC and PGA
(DACB[7:0] and PGAB[7:0])
Reserved.
MCLK
VSMP
VS
256
Figure 8 Peak Input Voltage to Match ADC Full-scale Range
DESCRIPTION
s
at the same time as V
3.5
2.5
1.5
0.5
3
2
1
0
0
GAIN REGISTER VALUE, PGA[7:0]
64
s
samples the video level in this
128
PD Rev 4.1 February 2005
192
Production Data
256
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