MAX16128 Datasheet, PDF (11/15 Pages) Maxim Integrated Products – Load-Dump/Reverse-Voltage Protection Circuits

MAX16128/MAX16129
Load-Dump/Reverse-Voltage Protection Circuits
To protect the gate of the MOSFETs, connect a zener
clamp diode from the gate to the source. The cathode
connects to the gate, and the anode connects to the
source. Choose the zener clamp voltage to be above 10V
and below the MOSFET V_GS maximum rating.
Increasing the Operating Voltage Range
The devices can tolerate -36V to +90V. To increase the
positive input-voltage protection range, connect two
back-to-back zener diodes from IN to GND, and connect
a resistor in series with IN and the power-supply input to
limit the current drawn by the zener diodes (see Figure
1).
Zener diode D1 clamps positive voltage excursions and
D2 clamps negative voltage excursions. Set the zener
voltages so the worst-case voltages do not exceed the
ratings of the part. Also ensure that the zener diode
power ratings are not exceeded. The combination of
the series resistor and the zener diodes also help snub
pulses on the supply voltage input and can aid in clamp-
ing the low-energy ISO 7637-2 pulses.
It is important to compute the peak power dissipation in
the series resistor. Most standard surface-mount resis-
tors are not able to withstand the peak power dissipa-
tion during certain pulse events. Check the resistor data
sheets for pulse-power derating curves. If necessary,
connect multiple resistors in parallel or use automotive-
rated resistors.
The shutdown input needs a series resistor to limit the
current if V_IN exceeds the clamped voltage on IN. A good
starting point is 100kI.
Output Reservoir Capacitor
The output capacitor can be used as a reservoir capaci-
tor to allow downstream circuitry to “ride out” fault
transient conditions. Since the voltage at the output is
protected from input-voltage transients, the capacitor
voltage rating can be less than the expected maximum
input voltage.
VBATT
R3
D1
D2
R3
100kI
100nF
10nF
GATE
IN
SHDN
SRC
MAX16128
MAX16129
GND
100I
OUT
DC-DC
CONVERTER
IN
OUT
10µF
GND
FLAG
Figure 1. Circuit to Increase Input-Voltage Protection Range
Maxim Integrated
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