BUF16821_1 Datasheet, PDF (20/30 Pages) Texas Instruments – Programmable Gamma-Voltage Generator and VCOM Calibrator with Integrated Two-Bank Memory

BUF16821
SBOS428B – JULY 2008 – REVISED MAY 2009 ............................................................................................................................................................... www.ti.com
OUTPUT PROTECTION
The BUF16821 output stages can safely source and
sink the current levels indicated in Figure 1 and
Figure 2. However, there are other modes where
precautions must be taken to prevent to the output
stages from being damaged by excessive current
flow. The outputs (OUT1 through OUT16, V_COM1 and
V_COM2) include ESD protection diodes, as shown in
Figure 18. Normally, these diodes do not conduct and
are passive during typical device operation. Unusual
operating conditions can occur where the diodes may
conduct, potentially subjecting them to high, even
damaging current levels. These conditions are most
likely to occur when a voltage applied to an output
exceeds (V_S) + 0.5V, or drops below GND – 0.5V.
One common scenario where this condition can occur
is when the output pin is connected to a sufficiently
large capacitor, and the BUF16821 power-supply
source (V_S) is suddenly removed. Removing the
power-supply source allows the capacitor to
discharge through the current-steering diodes. The
energy released during the high current flow period
causes the power dissipation limits of the diode to be
exceeded. Protection against the high current flow
may be provided by placing current-limiting resistors
in series with the output, as shown in Figure 10.
Select a resistor value that restricts the current level
to the maximum rating for the particular pin.
V_S
BUF16821
ESD Current
Steering Diodes
OUTX
or
V_COMX
Figure 18. Output Pins ESD Protection
Current-Steering Diodes
20
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