ht82v42 Holtek Semiconductor Inc., ht82v42 Datasheet - Page 9

• Manufacturer Part Number: ht82v42
• Description: Cis Analog Signal Processor
• Manufacturer: Holtek Semiconductor Inc.

CDS/CIS Processing
For CCD type input signals, the time at which the reset
level is sampled, is adjustable by setting control bits
CDSREF[1:0] as shown in the previous figure.
For CIS type input signals, non-CDS processing is
used. During this case, the video level is processed with
the voltage level on VRLC/VBIAS, the pin VRLC/VBIAS
is generated internally or externally. The VRLC/VBIAS
is sampled by Rs at the same time as Vs samples the
video level in this mode.
PGA Gain Registers
There are three PGA registers which are used to individ-
ually program the gain. Bits D7 through D0 control the
gain range in 256 increments. See the figure for a graph
Note: * Power-on default value
Rev. 1.00
MSB
D7
0
0
1
1
1
D6
0
1
1
1
1
D5
0
0
0
1
1
D4
0
1
0
0
1
PGA Gain Register Settings
D3
0
0
0
0
1
9
of the PGA gain versus PGA register code. The coding
for the PGA registers is a straight binary number, with all
zero words corresponding to the minimum gain setting
(0.68x) and all one words corresponding to the maxi-
mum gain setting (8x).
The PGA has a gain range from 0.68x (-3.3dB) to 8x
(18dB), adjustable in 256 steps. The Figure shows the
PGA gain as a function of the PGA register code. Al-
though the gain curve is approximately linear in dB, the
gain in V/V varies in nonlinear proportion with the regis-
ter code, according to the following the equation:
Gain (V/V) = 186 / (278-PGA[7:0])
Gain (dB) = 20LOG
D2
0
1
0
0
1
D1
0
0
0
0
1
10
(186/(278-PGA[7:0]))
LSB
D0
0
0
0
0
1
Gain(V/V) Gain (dB)
0.68
2.23
3.50
November 20, 2009
1
8
HT82V42
10.8
-3.3
18
0*
7