XRD98L23 Datasheet, PDF (8/32 Pages) Exar Corporation – 8-Bit, High-speed Linear CIS/CCD Sensor Signal Processor with Serial Control

XRD98L23
THEORY OF OPERATION
CIS Configuration (Contact Image Sensor)
The XRD98L23 has two configurations for CIS applications. Each configuration is set by the control registers
accessed through the serial port.
Mode 1. DC Coupled
If the CIS does not have leading or trailing black pixels as shown in Figure 2, then DC couple the CIS output to the
XRD98L23 input.
Optically Shielded
Pixels
Valid Pixels
Figure 2. Typical Output CIS Mode
Adjust the offset of the CIS (-60 mV to 300 mV) by setting the internal registers of the XRD98L23 to set the black
pixel value when the LEDs of the CIS are off. When the LEDs are on, use the XRD98L23 Programmable Gain to
maximize the ADCs dynamic range. Figure 3 shows a typical application for a CIS with an offset of -60mV to 300mV.
Rev. 1.00
8