VGA Port Companion Circuit
PACVGA105
©2010 SCILLC. All rights reserved. Publication Order Number:
May 2010 Rev. 2 PACVGA105/D
Features
• Seven channels of ESD protection designed to
meet IEC-1000-4-2 Level-4 ESD requirements
(±8kV contact discharge)
• Very low loading capacitance from ESD
protection diodes at less than 5pF typical
• TTL to CMOS level-translating buffers for the
HSYNC and VSYNC lines
• Three independent supply pins (V
CC
, V
RGB
and
V
AUX
) to facilitate operation with sub-micron
Graphics Controller ICs
• High impedance pull-ups (50kΩ nominal to V
AUX
)
for HSYNC and VSYNC inputs
• Pull-up resistors (1.8kΩ nominal to V
CC
) for
DDC_CLK and DDC_DATA lines
• Compact 16-pin QSOP package
• Lead-free version available
Applications
• ESD protection and termination resistors for VGA
(video) port interfaces
• Desktop PCs
• Notebook computers
• LCD monitors
Product Description
The PACVGA105 incorporates 7 channels of ESD
protection for signal lines commonly found in a VGA
port for PCs. ESD protection is implemented with
current steering diodes designed to safely handle the
high peak surge currents associated with the IEC-
1000-4-2 Level-4 ESD Protection Standard (±8kV
contact discharge). When the channels are subjected
to an electrostatic discharge, the ESD current pulse
is diverted via the protection diodes into the positive
supply rails or ground where they may be safely
dissipated.
The upper ESD diodes for the R, G and B channels
are connected to a separate supply rail (V
RGB
) to
facilitate interfacing to graphics controller ICs with low
voltage supplies. The remaining channels are
connected to the main 5V rail (V
CC
). The lower diodes
for the R, G and B channels are also connected to a
dedicated ground pin (GNDA) to minimize crosstalk
due to common ground impedance.
Two non-inverting buffers are also included in this IC
for buffering the HSYNC and VSYNC signals from
the graphics controller IC. These buffers will accept
TTL input levels and convert them to CMOS output
levels that swing between GND and V
CC
. These
drivers have a nominal 60
Ω output impedance to
match the characteristic impedance of the HSYNC
and VSYNC lines of the video cables typically used.
The inputs of these drivers also have high impedance
pull-ups (50kW nom.) pulling up to the V
AUX
rail. In
addition, the DDC_CLOCK and DDC_DATA
channels have 1.8k
Ω resistors pulling these inputs
up to the main 5V (V
CC
) rail.
剩余8页未读，继续阅读
资源评论
