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DESCRIPTION
The WM8253 is a 16-bit analogue front end/digitiser IC
which processes and digitises the analogue output signals
from CCD sensors or Contact Image Sensors (CIS) at pixel
sample rates of up to 6MSPS.
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
Analogue to Digital Converter. The digital output data is
available in 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 uses an analogue supply voltage of 3.3V and a
digital interface supply of between 2.5V and 3.3V. The
WM8253 typically only consumes 132mW when operating
from a single 3.3V supply.
WM8253
Single Channel 16-bit CIS/CCD AFE with 4-bit Wide Output
FEATURES
16-bit ADC
6MSPS conversion rate
Low power - 132mW typical
3.3V single supply or 3.3V/2.5V dual supply operation
Single channel operation
Correlated double sampling
Programmable gain (8-bit resolution)
Programmable offset adjust (8-bit resolution)
Programmable clamp voltage
4-bit wide multiplexed data output format
Internally generated voltage references
20-lead SSOP package
Serial control interface
APPLICATIONS
Flatbed and sheetfeed scanners
USB compatible scanners
Multi-function peripherals
High-performance CCD sensor interface
BLOCK DIAGRAM
VSMP
MCLK
AVDD
DVDD1
DVDD2
VRT
VRB
VREF/BIAS
TIMING GENERATION AND CONTROL
CL
R
S
V
S
WM8253
VINP
16-BIT
ADC
DATA
I/O
PORT
OP[0]
OP[1]
OP[2]
OP[3]/SDO
RLC
CDS
+
PGA
8
+
OFFSET
DAC
VRLC/VBIAS
RLC
DAC
4
8
MUX
R
G
B
R
MUX
G
B
I/P SIGNAL
POLARITY
ADJUST
CONFIGURABLE
SERIAL
CONTROL
INTERFACE
SDI
SCK
SEN
AGND1
AGND2
DGND
WOLFSON MICROELECTRONICS plc
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Production Data, August 2011, Rev 4.1
Copyright
2011
Wolfson Microelectronics plc
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
