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MAX9539/MAX9540
Detailed Description
The MAX9539/MAX9540 chipset provides a 3-wire
(RGB) interface for 5-wire (RGBHV) video by adding
and extracting the H, V, and composite sync from the
graphics video signals. This chipset eliminates the
problem of sync-to-video timing (skew errors) in a 5-
wire interface, while reducing the number of channels
required when transporting video signals.
The MAX9539 mixes the H and V sync signals and
adds them to create a 3-wire interface from a 5-wire
(RGBHV) input. The MAX9540 recovers the H and V
sync signals to create a 5-wire (RGBHV) interface from
the 3-wire input. The MAX9540 also provides a com-
posite sync output.
The chipset includes the MAX9539 sync adder and the
MAX9540 sync extractor with 180MHz large-signal
bandwidths to address display resolutions up to 1600 x
1200 at 85Hz for VGA-to-UXGA applications. Both
devices feature a DC-restore function, which virtually
eliminates any changes in black level. The chipset uses
a proprietary H and V sync addition/extraction scheme
(true sync) to minimize skew errors.
MAX9539 Sync Adder
The MAX9539 mixes the H and V sync signals and
adds them to create a 3-wire interface from a 5-wire
(RGBHV) input. Sync signals are added to the input
video signals. Horizontal sync is added to red video,
vertical sync is added to blue video, and composite
sync is added to green video. Composite sync is the
XOR function between H sync and V sync and is inter-
nally generated by the MAX9539. The sync level of the
video outputs is -2.4V. The DC-restore function
removes any DC offset (ΔVIN_RESTORE) in the RGB
video inputs and sets the output black level to 0V at the
back porch of the H sync. Therefore, the output black
level is set to 0V at the beginning of every line.
Figure 2 illustrates the functionality of the MAX9539. In
this example, the sync signals are of positive polarity.
MAX9540 Sync Extractor
The MAX9540 recovers the H and V sync signals to cre-
ate a 5-wire (RGBHV) interface from the 3-wire input. The
output video signals are obtained by removing the sync
pulses of the input video. The sync outputs correspond
to the sync pulses of the input video: horizontal sync is
Graphics Video Sync Adder/Extractor
8
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MAX9540 Pin Description
PIN
NAME
FUNCTION
1
IN_R
Red Video Input with Horizontal Sync
2, 7, 12
GND
Ground
3
REST_R
Red DC Restore. Connect a 1nF capacitor from REST_R to GND.
4, 9, 10, 14,
15, 20, 25
N.C.
No Connection. Not internally connected.
5
I.C.
Internally Connected. For best performance, connect this pin to GND.
6
IN_G
Green Video Input with Composite Sync
8
REST_G
Green DC Restore. Connect a 1nF capacitor from REST_G to GND.
11
IN_B
Blue Video Input with Vertical Sync
13
REST_B
Blue DC Restore. Connect a 1nF capacitor from REST_B to GND.
16
VSYNC
Vertical Sync Output
17
SP_V
Vertical Sync Polarity Input
18
OUT_B
Blue Video Output
19
VEE
Negative Power-Supply Input. Bypass with a 0.1F capacitor to GND.
21
CSYNC
Composite Sync Output
22
SP_C
Composite Sync Polarity Input
23
OUT_G
Green Video Output
24
VCC
Positive Power-Supply Input. Bypass with a 0.1F capacitor to GND.
26
HSYNC
Horizontal Sync Output
27
SP_H
Horizontal Sync Polarity Input
28
OUT_R
Red Video Output