WM8181
12-bit 2MSPS Serial Output CIS/CCD Digitiser
Advanced Information, January 2000, Rev 3.0
DESCRIPTION
The WM8181 is a 12-bit resolution, 2MSPS single channel image digitiser which is designed for easy interface to either CIS or CCD linear image sensors. Data is output in serial mode. The applied clock frequency (MCLK) equals the bit rate of the data output. The sample rate of the WM8181 can be either 1/12th or 1/16th of the applied master clock frequency.
The device can be configured for either single-ended or differential input operation. In single ended input mode, a reset clamp voltage can be applied to the analogue signal, under the control of a digital signal at the CLAMP pin. The WM8181 will accept either positive or negative-going video signals at any voltage between AGND and AVDD. The ADC references are internally generated. The range of these references may be derived internally using a bandgap generator or externally using the VREFIN pin.
The WM8181 is powered from either 3.3V or 5V single supplies. The device may also be powered from split 5V and 3.3V dual supplies. Typically, the WM8181 consumes 23mA supply current in normal operation. When the device is powered down, the supply current falls to less than 1µA.
The WM8181 is available in a 16-pin wide-body SOIC package.
FEATURES
• 12-bit 2MSPS ADC • No missing codes • Serial output • Simple clocking • Internal or external ADC reference range control • Accepts positive or negative video • Rail to rail input range • Reset-level clamp switch • 3.3V or 5V single supplies • 5V/3.3V dual supplies • 23mA supply current • 16-pin wide body SOIC package
APPLICATIONS
• USB bus powered scanners • Flatbed scanners • Sheetfeed scanners • Contact image sensors (CIS) • Linear CCDs
BLOCK DIAGRAM
AVDD (16)
VSMP (12)
MCLK (13)
WM8181
PD
TIMING AND POWER DOWN CONTROL
VINP (4)
VINM (5) CLAMP (11)
VREFIN (3)
SAMPLE/ HOLD
ADC
0.8*VDD + -
x1
1.5V BANDGAP
VRT/VRB GENERATOR
PARALLEL TO
12 SERIAL
(15) DVDD (14) DOUT (10) DGND
(1) (2) AGND1 AGND2
(7) VRT
(6) VRB
WOLFSON MICROELECTRONICS LTD
Lutton Court, Bernard Terrace, Edinburgh, EH8 9NX, UK Tel: +44 (0) 131 667 9386 Fax: +44 (0) 131 667 5176 Email:
[email protected] http://www.wolfson.co.uk
Advanced Information data sheets contain preliminary data on new products in the preproduction phase of development.
Supplementary data will be published at a later date.
2000 Wolfson Microelectronics Ltd.
WM8181
Advanced Information
PIN CONFIGURATION
AGND1
1
16 AVDD
ORDERING INFORMATION
DEVICE XWM8181CDW
TEMP. RANGE 0 to 70oC
PACKAGE
16-pin SOIC wide body
AGND2 VREFIN
2 3
15 DVDD 14 DOUT
VINP
4
13 MCLK
VINM VRB
5 6
12 VSMP 11 CLAMP
VRT 7 NC 8
10 DGND 9 NC
PIN DESCRIPTION
PIN NAME
TYPE
DESCRIPTION
1 AGND1
Ground
General analogue ground (0V).
2 AGND2
Ground
Reference analogue ground (0V).
3 VREFIN Analogue input Allows external control of the ADC references.
4
VINP
Analogue input Positive video input
5
VI.