XRD98L23
13
Rev. 1.00
R
L
VRT
VRB
VDD
XRD98L23
CLAMP
RINT
RED
M
U
X
C
I
S
REXT
CEXT
N/C
N/C
N/C
Therefore, Tc =1/R
INT
C
EXT
If the input to the external capacitor has a source
impedance (R
EXT
), then:
T
c
=1/(R
INT
+R
EXT
)C
EXT
This value corresponds to the black reference of the
image sensor. When the CLAMP pin is set back to low,
the ADC samples the video signal with respect to the
black reference. The typical value for the external
capacitor is 100pF. This value should be adjusted
according to the time constant (Tc) needed in a particu-
lar application. The CLAMP pin has an internal 180 ohm
(from electrical tabels) impedance (R
INT
) which is in
series with the external capacitor (C
EXT
).
Figure 7. CIS AC Coupled Application
