XRD98L61(2000) View Datasheet(PDF) - Exar Corporation

Part Name

Description

Manufacturer

XRD98L61
(Rev.:2000)

CCD Image Digitizers with CDS, PGA and 12-Bit A/D

Exar Corporation 

XRD98L61

Preliminary

Programmable Gain Amplifier (PGA)

The PGA provides gains from 0dB to 36 dB in approximately 0.047 dB steps. The desired gain setting is

programmed via the 10 bit gain register in the Serial Interface.

For gain codes between 0 and 767 the gain can be calculated by the following equation:

Gain[dB]

=





Code

768

×

36



For gain codes ≥ 768 the gain is fixed at 36 dB. The gain doubles every 128 codes to simplify DSP algorithms and

control.

36

30

27

24

18

12

9

6

0

0

Gain Code, PGA[9:0]

Figure 6. PGA Gain vs. Gain Code

An example of setting the gain is as follows: If the CCD input is limited by 800mVpp (CDSVIN) and the ADC full

scale differential input (VID) is 2Vpp, then a minimum gain is calculated by:

 VID 

2 

Gain = 20 log 

 = 20 log 

 = 8dB

 CDSVIN 

 0.8 

The gain code would be set to 170d for 8dB of PGA gain.

Rev. P4.00

18

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