TLC8044 Datasheet, PDF (29/32 Pages) Texas Instruments – 12-BIT ANALOG-TO-DIGITAL INTERFACE FOR CHARGE-COUPLED DEVICE IMAGE SENSORS FOR SCANNERS

TLC8044
12-BIT ANALOG-TO-DIGITAL INTERFACE FOR
CHARGE-COUPLED DEVICE IMAGE SENSORS FOR SCANNERS
SLAS128 – JUNE 1997
APPLICATION INFORMATION
running the TLC8044 at 4-megasamples/sec in CDS monochrome mode
The TLC8044 can be set up to provide a 4-megasample/sec throughput when in CDS monochrome mode;
however, the VSMP input must run continuously at 4 MHz.
The following paragraphs describe operation of the TLC8044 in monochrome mode (sampling one channel
only). The maximum sample rate in color CDS mode is 2-megasamples/channel/sec.
In CDS mode, the video signal is sampled both during the reset phase and when video information is present
with timing defined to a VSMP input. The difference between these two samples forms the input to the ADC.
In monochrome mode, all samples are taken from one input video channel. The device is set up as listed in Table
6. See Tables 4 and 5 for offset DAC values in CDS mode.
System timing is shown in Figure 18. MCLK clocks the device at 12 MHz (as normal). VSMP, which controls
the sample rate, is run at 4 MHz. A reset sample is taken on the rising edge of MCLK after VSMP is asserted.
The corresponding video sample is taken on the next MCLK rising edge. Compensation coefficients (pixel offset
and pixel shading) are sampled on the falling edge of MCLK 26.5 periods after the initial reset sample. The
processed digital outputs appear on OP0–OP15 41.5 MCLK periods after the initial reset sample.
In Figure 18 the system timing diagram shows a negative-going video sample. The polarity of the ADC output
signal can be inverted under control of the serial interface. Setup and hold times are specified in the
recommended operating conditions table.
Table 7. Relevant Register Settings
REGISTER
BITS
Setup
register 1
ENADC
BICLIP
ADCMX
MONO
DEFPG
DEFPO
DNS
INVADC
CDS
Setup
register 2
POSCL1,0
WLSEL1,0
THSEL1,0
CDSREF1,0
CHAN1,0
† _{U = User defined}
VALUE†
U
U
0
1
U
U
0
U
1
UU
UU
UU
00
UU
DESCRIPTION
ADC standby control
Select unipolar clip
ADC MUX control
Monochrome operation
Select default pixel gain
Select default pixel offsets
Select single-ended mode
ADC output polarity
Select correlated double sampling mode
Pixel offset scaling
Select 12-bit output word
Three channel
Advance one MCLK period
Select channel to be sampled
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