VS6552 datasheet(6/26 Pages) STMICROELECTRONICS

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VS6552

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3 FUNCTIONAL DESCRIPTION

The first sections of this chapter detail the main

blocks in the device:

■ Analog video block

■ Digital video block

The later sections of this chapter describe other

functional aspects of the device. Device level op-

erating modes, including suspend, are detailed

3.1 Analog Video Block

3.1.1 Features

■ ADC: 10-bit A/D converter - SRAM readout

■ Dynamic range 60 dB (typical)

■ SNR 37 dB @ 50 cd.m

2 (typical)

Figure 2. Analog Video Block

3.1.2 Analogue Block Diagram

The analog video block from Figure 4, consists of

a VGA resolution pixel array, power management

circuitry. The digital block provides all timing sig-

nals to drive the analog block.

Pixel voltage values are read out and digitized us-

ing the address decoders and column ADC

3.2 Digital Video Block

3.2.1 Features

■ Frame rate: 30 frame/s max. (VGA) can be

reduced down to less than 3 frame/s (VGA)

■ Automatic dark calibration to ensure consistent

video level over varying scenes

■ Fixed pattern noise (FPN) data gathering

■ Line and frame statistics gathering

■ On-chip Power-On-Reset cell

■ Single video output format: VGA 640 x 480

■ H - Scaler function to aid software only

viewfinder implementations

3.2.2 Dark Calibration Algorithm

VS6552 runs a dark calibration algorithm on the

raw image data to control the video offsets caused

by dark current. This ensures that a high quality

image is output over a range of operating condi-

tions. First frame dark level is correctly calibrated,

for subsequent frames the adjustment of the dark

level is damped by a leaky integrator function to

avoid possible frame to frame flicker.

VGA

pixel

array

Y address

Digital

logic

raw sensor data

Timing signals

Power

management

Column ADC

X-Address

SRAM readout

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