Single Channel CCD/CIS ADC

The WM8255 is a 16-bit analog front end/digitizer IC which processes and digitizes the analog output signals from CCD sensors or Contact Image Sensors (CIS) at pixel sample rates of up to 12 MSPS. The device includes a complete signal processing channel containing reset level clamping, correlated double sampling, programmable gain and offset adjust functions. Internal multiplexers allow fast switching of offset and gain for line-by-line colour processing. The output from this channel is time multiplexed into a high-speed 16-bit analog to digital converter. The digital output data is available in a 2 bit or 4-bit wide multiplexed format. An internal 4-bit DAC is supplied for internal reference level generation. This may be used during CDS to reference CIS signals or during reset level clamping to clamp CCD signals. An external reference level may also be supplied. ADC references are generated internally, ensuring optimum performance from the device. The device includes an RGB LED current drive using current and PWM functionality to control the operation of sensor LEDs. The device typically uses an analog supply voltage of 5.75V and a digital interface supply of 3.3V.



Imaging A/D Converters


  • 16-bit ADC
  • 12 MSPS conversion rate
  • Low power – 250 mW typical
  • 5.75V and 3.3V supply operation
  • Single channel operation
  • Correlated double sampling
  • Programmable gain (8-bit resolution)
  • Programmable offset adjust (8-bit resolution)
  • Programmable clamp voltage
  • RGB LED current drive using current and PWM
  • 2-bit or 4-bit wide multiplexed data output format
  • Internally generated voltage references
  • 28-lead QFN package
  • 3 wire serial control interface

Parametric Specifications

Resolution (bits) 16
Speed (MSPS) 12
Input PGA (bits) 8
Output Format 4+4+4+4 bit (nibble);
2+2+2+2+2+2+2+2 bit
Supply (V) 4.75-6;
Power Consumption (mW) 236
Package 28 QFN

Design Resources

WAN-0118 Guidelines

WAN_0118 rev 2.5 : 740 kb


Comprehensive Solutions