WM8213_08 Datasheet, PDF (14/38 Pages) Wolfson Microelectronics plc – 24MSPS 16-bit CCD Digitiser

WM8213
Production Data
DEVICE DESCRIPTION
INTRODUCTION
A block diagram of the device showing the signal path is presented on the front page of this
datasheet.
The WM8213 samples up to three inputs (RINP, GINP and BINP) simultaneously. The device then
processes the sampled video signal with respect to the video reset level or an internally/externally
generated reference level using between one and three processing channels.
Each processing channel consists of an Input Sampling block with optional Reset Level Clamping
(RLC) and Correlated Double Sampling (CDS), an 8-bit programmable offset DAC and a 9-bit
Programmable Gain Amplifier (PGA).
The ADC then converts each resulting analogue signal to a 16-bit digital word. The digital output from
the ADC is presented on an 8-bit wide bus.
On-chip control registers determine the configuration of the device, including the offsets and gains
applied to each channel. These registers are programmable via a serial interface.
The WM8213 has been designed to have a high degree of compatibility with previous generations of
Wolfson AFEs. By setting the LEGACY register bit the device adopts the same timing as the
WM819x and WM815x families of AFEs. The control interface is also compatible.
INPUT SAMPLING
The WM8213 can sample and process one to three inputs through one to three processing channels
as follows:
Colour Pixel-by-Pixel: The three inputs (RINP, GINP and BINP) are simultaneously sampled for
each pixel and a separate channel processes each input. The signals are then multiplexed into the
ADC, which converts all three inputs within the pixel period.
Two Channel Pixel-by-pixel: Two input channels (RINP and GINP) are simultaneously sampled for
each pixel and a separate channel processes each input. The signals are then multiplexed into the
ADC, which converts both inputs within the pixel period. The unused Blue channel is powered down
when this mode is selected.
Monochrome: A single chosen input (RINP, GINP, or BINP) is sampled, processed by the
corresponding channel, and converted by the ADC. The choice of input and channel can be changed
via the control interface, e.g. on a line-by-line basis if required. The unused channels are powered
down when this mode is selected.
Colour Line-by-Line: A single input (RINP) is sampled and multiplexed into the red channel for
processing before being converted by the ADC. The registers which are applied to the PGA and
Offset DAC can be switched in turn (RINP → GINP → BINP → RINP…) by applying pulses to the
RSMP pin. This is known as auto-cycling. Alternatively, other sequences can be generated via the
control registers. This mode causes the unused blue and green channels to be powered down. Refer
to the Line-by-Line Operation section for more details.
w
PD Rev 4.1 July 2008
14