wm8215 Wolfson Microelectronics plc, wm8215 Datasheet - Page 15

• Manufacturer Part Number: wm8215
• Description: 60msps 10-bit 3-channel Ccd Digitiser
• Manufacturer: Wolfson Microelectronics plc

WM8215
Figure 10 Reset Level Clamp Operation (CLAMPCTRL=1), non-CDS mode only
Table 2 Reset Level Clamp Control Summary
w
(RLCEN=1,CLMPCTRL=1)
RLCEN
0
1
1
RLC switch control,
INPUT VIDEO
CLAMPCTRL
"CLMP"
SIGNAL
MCLK
VSMP
RSMP
X
0
1
RLC is not enabled. RLC switch is always open.
RLC switch is controlled directly from RSMP input
pin:
VSMP applied as normal, RSMP is used to
indicate the location of black pixels
RLC switch is controlled by logical combination of
RSMP and VSMP:
start or end of a line on most image sensors). This is known as line-clamping and relies on the input
capacitor to hold the DC level between clamp intervals. In non-CDS mode (CDS=0) this can be done
directly by controlling the RSMP input pin to go high during the black pixels only.
Alternatively it is possible to use RSMP to identify the black pixels and enable the clamp at the same
time as the input is being sampled (i.e. when VSMP is high and RSMP is high). This mode is
enabled by setting CLAMPCTRL=1 and the operation is shown in Figure 10.
Video and reference sample
taken on fallling edge of VSMP
RSMP=0: switch is open
RMSP=1: switch is closed
RSMP && VSMP = 0: switch is open
RSMP && VSMP = 1: switch is closed
unstable
reference level
OUTCOME
"black" pixel
dummy or
RLC switch closed when RSMP=1 &&
VSMP=1 (during "black" pixels)
When input is DC coupled and within supply
rails.
When user explicitly provides a reset sample
signal and the input video waveform has a
suitable reset level.
When clamping during the video period of black
pixels or there is no stable per-pixel reference
level.
This method of operation is generally only
sensible in non-CDS mode.
PD, Rev 4.2, February 2009
USE
video level
Production Data
15