WM8214 Datasheet, PDF (15/35 Pages) Wolfson Microelectronics plc – 40MSPS 16 BIT CCD DIGITISER

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WM8214
RINP
or
GINP
C_IN
or
BINP
RLC
switch
closed=
50 Ohm
CLMP
CDS=1
CDS=0
VS
'Video'
sample
capacitor
RS (if CDS=1) or
VS (if CDS=0)
'Reference'
sample
capacitor
CONTROL
INTERFACE
CDS
VRLC/
VBIAS
4-BIT
CDAC
EN
CDAC[4:0]
CDACEN
Figure 9 CDS/non-CDS Input Configuration
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 a 9-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 WM8214 PGA is shown in Figure 10. Figure 11 shows the maximum
device input voltage that can be gained up to match the ADC full-scale input range (default=2V).
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 RSMP pin, or controlled via the ACYC and
INTM[1:0] bits. Refer to the Line-by-Line Operation section for more details.
w
PP Rev 1.6 March 2004
15