WM8170 datasheet(15/41 Pages) WOLFSON

15 / 41 page

WM8170

Product Preview Rev 1.0

WOLFSON MICROELECTRONICS LTD

PP Rev 1.0 March 2000

INPUT BLANKING

In some cases the output signals from the CCD can be larger than the input stage of WM8170 could

normally handle without overload and saturation. To avoid this situation the Sample/Hold stage is

preceded by a pair of analogue switches, which can be used to block the analogue input signals at

PIN and DIN from passing to the Sample/Hold stage. These switches are turned on or off by placing

a high or low level on the PBLK pin respectively.

RESET LEVEL CLAMP OR AC COUPLING

The input video can be interfaced via a capacitor to the WM8170 by two methods. A Reset Level

Clamp facility is provided which can be used in both Sample and Hold and in CDS modes of

operation. The clamp switch is closed if a low level is applied to both CLPENB and CLPSWB digital

inputs. The clamp voltage, VCLP, can be programmed via the management interface to be equal to

VRB, VMID, or VRT. A typical use of the Reset Level Clamp facility using CDS is shown in Figure 12.

Alternatively, the CLPENB and CLPSWB digital inputs can be tied high, which will disable the Reset

Level Clamp switch, and the control bit ACINP set. This control bit connects an internal AC coupling

resistor to the DIN input, which allows the user to simply AC couple the analogue video signal into the

WM8170. If CDS is also used, then any drift on the WM8170 side of the coupling capacitor due to

input video DC content will be removed.

CLPENB

CLPSWB

RESET

S/H

SIGNAL

S/H

DIFFERENTIAL SIGNAL

TO GAIN BLOCK

SHD

SHP

PBLK

DIN

50k

ACINP

VMID

VCLP

VMID

CORRELATED DOUBLE

SAMPLING

INVSHX

Figure 9 Input Sample/Hold and Reset Level Clamp Block Diagram

VIDEO

VIDEO SAMPLE, SHD

INVSHX=0

REFERENCE SAMPLE, SHP

INVSHX=0

Figure 10 Input Sample/Hold Timing, INVSHX = 0

WM8170 bảng dữ liệu(PDF) 15 Page - Wolfson Microelectronics plc

WM8170 bảng dữ liệu(HTML) 15 Page - Wolfson Microelectronics plc

Html Pages

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 29 30 31 32 33 34 35 36 37 38 39 40 41

bảng dữ liệu tải về

Link URL