XRD98L61_01 Datasheet, PDF(18/38 Page) Exar Corporation – CCD Image Digitizers with CDS, PGA and 12-Bit A/D

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

XRD98L61_01 Datasheet, PDF (18/38 Pages) Exar Corporation – CCD Image Digitizers with CDS, PGA and 12-Bit A/D

◁

XRD98L61

4.0 Programmable Gain Amplifier (PGA)

The PGA provides gains from 0dB to 36 dB in approxi-

mately 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]

ï£¬ï£«

ï£

Code

768

ï£·ï£¶

ï£¸

For gain codes â¥ 768, the gain is fixed at 36 dB. The

gain doubles every 128 codes to simplify DSP algo-

rithms and control.

Gain Code, PGA[9:0]

Figure 7. 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:

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

gain.

ï£«

Gain = 20 log ï£¬

ï£

VID

CDSV IN

ï£¶

ï£«

ï£· = 20 log ï£¬

ï£¸

ï£

0.8

ï£¶

ï£· = 8dB

ï£¸

Rev. 2.00

▷