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PDF WM8255 Data sheet ( Hoja de datos )
| Número de pieza | WM8255 | |
| Descripción | Single Channel 16-bit CIS/CCD AFE | |
| Fabricantes | Wolfson | |
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WM8255
Single Channel 16-bit CIS/CCD AFE with RGB LED Current Drive
DESCRIPTION
The WM8255 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 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
Analogue 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 analogue supply voltage of
5.75V and a digital interface supply of 3.3V.
BLOCK DIAGRAM
FEATURES
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
APPLICATIONS
Flatbed and sheetfeed scanners
USB compatible scanners
Multi-function peripherals
WOLFSON MICROELECTRONICS plc
Production Data, August 2013, Rev 4.7
Copyright 2013 Wolfson Microelectronics plc
1 page  
WM8255
Production Data
PIN DESCRIPTION
PIN NO
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
NAME
MCLK
TYPE
Digital input
OP[3]/SDO
OP[2]
OP[1]
OP[0]
Digital output
Digital output
Digital output
Digital output
DVDD
DGND
EXTRES
Supply
Supply
Analogue input
VRB
Analogue output
VRT
Analogue output
VRX
Analogue output
NC
AGND2
AVDD2
No Connect
Supply
Supply
VINP
Analogue input
VRLC/VBIAS Analogue I/O
ILEDB
ILEDG
ILEDR
AVDD1
AGND1
TG
LEDSTART
NC
SDI
SCK
SEN
VSMP
Analogue input
Analogue input
Analogue input
Supply
Supply
Digital input
Digital input
No Connect
Digital input
Digital input
Digital input
Digital input
DESCRIPTION
Master clock. This clock is applied at N times the input pixel rate (N = 2, 3, 4, 6, 8 or
any multiple of 2 thereafter depending on input sample mode).
Digital multiplexed output data bus.
ADC output data (d15:d0) is available in a 4-bit multiplexed format as shown below.
A 2-bit multiplexed output is also available as described in the OUTPUT FORMATS
section of this datasheet on page 18.
A BC
D
d15 d11 d7
d3
d14 d10 d6
d2
d13 d9 d5
d1
d12 d8 d4
d0
Alternatively, pin OP[3]/SDO may be used to output register read-back data when
address bit 4=1 and SEN has been pulsed high. See Serial Interface description in
Device Description section for further details.
Digital supply (3.3V)
Digital ground (0V).
External resistor connection for LED absolute current control. Must be connected to
ground via a suitable resistor.
Lower reference voltage.
This pin must be connected to AGND via a decoupling capacitor.
Upper reference voltage.
This pin must be connected to AGND via a decoupling capacitor.
Input return bias voltage
This pin must be connected to AGND via a decoupling capacitor.
Not Connected.
Analogue ground pin (0V)
Analogue supply (3.3V) Not required to be driven if AVDD1 is being used. A
decoupling capacitor must be connected to AGND.
Video input.
Selectable analogue output voltage for RLC or single-ended bias reference.
This pin would typically be connected to AGND via a decoupling capacitor.
VRLC can be externally driven if programmed Hi-Z.
Blue LED pin
Green LED pin
Red LED pin
Analogue Supply (5.75V)
Analogue ground (0V).
Line synchronisation pulse
LED start pulse
Not Connected.
Serial data input.
Serial clock
Enables the serial interface when high.
Video sample synchronisation pulse.
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PD, Rev 4.7, August 2013
5
5 Page 
WM8255
SERIAL INTERFACE
Production Data
SCK
SDI
SEN
SDO
tSPER
tSSU
tSH
tSCKL tSCKH
tSCE
ADC DATA
tSEW tSEC
tSERD
tSCRD
t SCRDZ
MSB
LSB
REGISTER DATA
ADC
DATA
Figure 3 Serial Interface Timing
Test Conditions
AVDD1 = 5.75V, DVDD = 3.3V, AGND = DGND = AVDD2 = 0V, TA = 25C, MCLK = 24MHz unless otherwise stated.
PARAMETER
SYMBOL TEST CONDITIONS
SCK period
tSPER
SCK high
tSCKH
SCK low
tSCKL
SDI set-up time
tSSU
SDI hold time
tSH
SCK to SEN set-up time
tSCE
SEN to SCK set-up time
tSEC
SEN pulse width
tSEW
SEN low to SDO = Register data
tSERD
SCK low to SDO = Register data
tSCRD
SCK low to SDO = ADC data
tSCRDZ
Note:
1. Parameters are measured at 50% of the rising/falling edge
MIN
41.6
18.8
18.8
6
6
12
12
25
TYP
MAX
30
30
30
UNITS
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
ns
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PD, Rev 4.7, August 2013
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet WM8255.PDF ] | |
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