PAS302BCA-32

CMOS Image Sensor IC

Version 2.3, 13 Sep. 2004

PixArt Imaging Inc.

E-mail: fae_service@pixart.com.tw

4

2. Block Diagram

Sensor Array

644x484

CDS

Column Decoder

F G

C G

G G

10-Bit

A/D

Timing Generator & Control Logic

Defect

Compensation

Digital Gain

Stage

DAC1

DAC2

Front Gain

Color Gain

Global Gain

3-Bit

x2 ~ x4

4-Bit

x1 ~ x2

4-Bit

x1 ~ x2

Companding

Figure 2.1. PAS302BCA-32 sensor block diagram

The PAS302BCA-32 is a 1/4” CMOS imaging sensor with 644x488 physical pixels. The active

region of sensor array is 644x484 as shown in Fig. 2.1. The sensor array is covered with Bayer

pattern color filters and micro-lens. The first pixel location <0,0> is programmable in 2 direction

(X and Y) and the default value is at the left-down side of sensor array.

After a programmable exposure time, the signals of image are sampled first with CDS

(Correlated Double Sampling) block to improve S/N ratio and reduce fixed pattern noise.

Three analog gain stages are implemented before signals are transferred to 10-Bit ADC. The

front gain stage (FG) can be programmed to fit the saturation level of sensor to the full-range

input of ADC. The programmable color gain stage (CG) is used to balance the luminance

response difference between B, G and R color. The global gain stage (GG) is programmed to

adapt the gain to the image luminance.

After three gain stages, the signals will be digitized by the on-chip 10-Bit ADC. After the image

data have been digitized, further adjustment to the signal can be applied before the data is

output to next stage.