WM8181 查看數據表（PDF） - Wolfson Microelectronics plc

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WM8181

12-bit 2MSPS Serial Output CIS/CCD Digitiser

Wolfson Microelectronics plc 

WM8181

VOUT

CIS

SENSOR

BLACK

REFERENCE

LEVEL

VINP

MCLK

VSMP

WM8181

DOUT

VINM

CLAMP

VREFIN VRT VRB

Advanced Information

SYSTEM

ASIC

EXACT CIRCUITRY

MAY VARY

DEPENDING ON

SENSOR USED

SET VOLTAGE TO MATCH VPP FROM

SENSOR OR TIE TO AVDD TO SET

FULL-SCALE INPUT TO 1.5V

Figure 6 d.c. Coupled Positive Video

Some of the newer CIS devices have a reference voltage that corresponds closely to the black level.

In most cases this reference voltage cannot be applied directly to the VINM pin because the black

video output can go below this value and will be outside the range of the ADC. To overcome this,

VINM should be driven from a voltage that is slightly more negative than the CIS reference voltage.

This is shown in Figure 7. The input current to VINM is small but care should be taken to ensure that

R2 and R3 do not load the CIS reference circuit.

VOUT

CIS

SENSOR

VREF

VINP

MCLK

VSMP

WM8181

DOUT

VINM

CLAMP

VREFIN VRT VRB

SYSTEM

ASIC

EXACT CIRCUITRY

MAY VARY

DEPENDING ON

SENSOR USED

SET VOLTAGE TO MATCH VPP FROM

SENSOR OR TIE TO AVDD TO SET

FULL-SCALE INPUT TO 1.5V

Figure 7 CIS with Reference Voltage

WOLFSON MICROELECTRONICS LTD

AI Rev 3.0 January 2000

10

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