AD9882 Analog Devices, AD9882 Datasheet - Page 10

• Manufacturer Part Number: AD9882
• Description: Dual Interface for Flat Panel Displays
• Manufacturer: Analog Devices

AD9882
PIN FUNCTION DETAIL (ANALOG INTERFACE)
INPUTS
R
G
B
HSYNC
VSYNC
SOGIN
AIN
AIN
AIN
Analog Input for RED Channel
Analog Input for GREEN Channel
Analog Input for BLUE Channel
High impedance inputs that accept the RED,
GREEN, and BLUE channel graphics signals,
respectively. For RGB, the three channels are
identical and can be used for any colors, but
colors are assigned for convenient reference.
For proper 4:2:2 formatting in a YPbPr application,
the Y must be connected to the G
Pb must be connected to the B
Pr must be connected to the R
They accommodate input signals ranging from
0.5 V to 1.0 V full scale. Signals should be
ac-coupled to these pins to support clamp
operation.
Horizontal Sync Input
This input receives a logic signal that establishes
the horizontal timing reference and provides the
frequency reference for pixel clock generation.
The logic sense of this pin is controlled by Serial
Register Bit 10H, Bit 6 (Hsync Polarity). Only
the leading edge of Hsync is active; the trailing
edge is ignored. When Hsync Polarity = 0, the
falling edge of Hsync is used. When Hsync
Polarity = 1, the rising edge is active.
The input includes a Schmitt trigger for noise
immunity, with a nominal input threshold of
1.5 V.
Electrostatic Discharge (ESD) protection diodes
will conduct heavily if this pin is driven more
than 0.5 V above the maximum tolerance voltage
(3.3 V), or more than 0.5 V below ground.
Vertical Sync Input
This is the input for vertical sync.
Sync-on-Green Input
This input is provided to assist with processing
signals with embedded sync, typically on the
GREEN channel. The pin is connected to a
high speed comparator with an internally gener-
ated threshold, which is set by the value of
register 0FH, Bits 7–3.
When connected to an ac-coupled graphics
signal with embedded sync, it will produce a
noninverting digital output on SOGOUT.
When not used, this input should be left uncon-
nected. For more details on this function and
how it should be configured, refer to the Sync-
on-Green section.
AIN
AIN
input.
AIN
input, and the
input, the
–10–
SOGOUT
FILT
REFBYPASS Internal Reference BYPASS
MIDBYPASS Midscale Voltage Reference BYPASS
HSOUT
DATACK
VSOUT
Sync-on-Green Slicer Output
This pin can be programmed to produce either
the output from the Sync-on-Green slicer com-
parator or an unprocessed but delayed version of
the Hsync input. See the Sync Processing Block
Diagram, Figure 18, to view how this pin is
connected.
Note: The output from this pin is the composite
SYNC without additional processing from the
AD9882.
External Filter Connection
For proper operation, the pixel clock generator
PLL requires an external filter. Connect the
filter shown in Figure 6 to this pin. For optimal
performance, minimize noise and parasitics on
this node.
Bypass for the internal 1.25 V band gap refer-
ence. It should be connected to ground through
a 0.1 mF capacitor.
The absolute accuracy of this reference is ± 4%,
and the temperature coefficient is ± 50 ppm,
which is adequate for most AD9882 applica-
tions. If higher accuracy is required, an external
reference may be employed instead.
Bypass for the internal midscale voltage refer-
ence. It should be connected to ground through
a 0.1 mF capacitor. The exact voltage varies with
the gain setting of the RED channel.
Horizontal Sync Output
A reconstructed and phase-aligned version of
the Hsync input. The duration of Hsync can
only be programmed on the analog interface,
not the digital.
Data Output Clock
The data clock output signal is used to clock the
output data and HSOUT into external logic.
It is produced by the internal clock generator
and is synchronous with the internal pixel
sampling clock.
When the sampling time is changed by adjusting
the PHASE register, the output timing is shifted
as well. The Data, DATACK, and HSOUT
outputs are all moved so the timing relationship
among the signals is maintained.
Vertical Sync Output
The separated Vsync from a composite signal or
a direct pass-through of the Vsync input. The
polarity of this output can be controlled via
Register 10H, Bit 2. The placement and duration
in all modes is set by the graphics transmitter.
REV. A