CS7622 データシートの表示（PDF） - Cirrus Logic

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CS7622

CCD Imager Analog Processor

Cirrus Logic 

CS7622

would be “1100000000000.” The transfer function

of the Vin/gain adjust out is shown in Figure 11.

A block diagram of the gain adjust block is shown

in Figure 12.

Since the analog gain changes do not match the

digital shifts exactly, there is a potential to have

non-monotonic digital output. In order to remove

this problem, calibration is performed. During cal-

ibration, offset values are found that will be used to

counteract the errors caused by the analog gain

mismatch. Using these offset values, the final out-

put is a monotonic continuous 13-bit value.

3.4 13-to-10 Bit Compander

While a 13 bit output may be useful in some appli-

cations, others may require the standard 10 bit out-

put. To accommodate this and yet still retain the

advantages of the increased dynamic range, a 13-

to-10 (or 13-to-12) bit compander is included. By

using the picture content as a guide, the user can se-

lect which curve will lead to the best overall dy-

namic range in the picture. The Companding

module takes 13-bit data as input, and outputs ei-

ther 10-bit companded data, 12-bit MSB-clipped

data or it lets the original 13-bit data pass through.

By programming the compander in the way that is

shown in Figure 13, it is possible to compensate for

DIG ADJUST OUT (13 BITS)

8192

4096

8X 4X

2X

1X

2048

1024

0

0.125 0.25

0.5

00 01

10

1.0

VIN (V)

11

ADC OUTPUT

Figure 11. Transfer function of Vin to Gain Adjust output Block (assuming full scale level of 1.0 V)

VGA_ADC OUTPUT

ADC OUTPUT

10

2

GAIN ADJUST

13

TO DIGITAL GAIN

SHIFT BY 0,1,2, OR 3

Figure 12. Gain Adjust output Block

12

DS322PP1

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