wm8215 Wolfson Microelectronics plc, wm8215 Datasheet - Page 17

• Manufacturer Part Number: wm8215
• Description: 60msps 10-bit 3-channel Ccd Digitiser
• Manufacturer: Wolfson Microelectronics plc

WM8215
ADC INPUT BLACK LEVEL ADJUST
Figure 14 ADC Input Black Level Adjust Settings
w
Figure 12 PGA Gain Characteristic
8
7
6
5
4
3
2
1
0
0
128
Gain Code (PGA[8:0])
The output from the PGA can be offset to match the full-scale range of the differential ADC (2*[VRT-
VRB]).
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. This will give an output
code of 3FF (hex) from the WM8215 for zero input. If code zero is required for zero differential input
then the INVOP bit should be set.
For positive going input signals the black level should be offset to the bottom of the ADC range by
setting PGAFS[1:0]=11. This will give an output code of 000 (hex) from the WM8215 for zero input.
256
384
512
Figure 13 Peak Input Voltage to Match ADC Full-scale Range
3.5
2.5
1.5
0.5
3
2
1
0
0
128
Gain Code (PGA[8:0])
256
PD, Rev 4.2, February 2009
Max i/p V oltage
LOWREFS=0
Max i/p V oltage
LOWREFS=1
384
Production Data
512
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