MAX6399 MAXIM [Maxim Integrated Products], MAX6399 Datasheet - Page 8

• Manufacturer Part Number: MAX6399
• Description: High-Voltage, Overvoltage/Undervoltage, Protection Switch Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

Use a diode or p-channel MOSFET to protect the
MAX6399 during a reverse voltage insertion (Figures 8a,
8b). Low p-channel MOSFET on-resistance of 30mΩ or
less yields a forward-voltage drop of only a few millivolts
(versus hundreds of millivolts for a diode, Figure 8a)
thus improving efficiency in battery-operated devices.
High-Voltage, Overvoltage/Undervoltage,
Protection Switch Controller
Figure 5. The MAX6399 Controlling GATE Inrush Current
Figure 7. Protecting the MAX6399 Input from High-Voltage
Transients
8
V
V
IN
BATT
_______________________________________________________________________________________
60V
TVS
MAX6399
GND
IN
GATE
OUT
MAX6399
Reverse Voltage Protection
GND
C
IN
GATE
1kΩ
GATE
OUT
IN
CONVERTER
DC-DC
GND
OUT
C
LOAD
LOAD
LOAD
Connecting a positive battery voltage to the drain of Q1
(Figure 8b) produces forward bias in its body diode,
which clamps the source voltage one diode drop below
the drain voltage. When the source voltage exceeds
Q1’s threshold voltage, Q1 turns on. Once the FET is
on, the battery is fully connected to the system and can
deliver power to the device and the load.
An incorrectly inserted battery reverse-biases the FET’s
body diode. The gate remains at the ground potential.
The FET remains off and disconnects the reversed bat-
tery from the system. The zener diode and resistor com-
bination prevent damage to the p-channel MOSFET
during an overvoltage condition.
The MAX6399 thermal-shutdown feature monitors the
PC board temperature of the external MOSFET when
the devices sit on the same thermal island. Good ther-
mal contact between the MAX6399 and the external
n-channel MOSFET is essential for the thermal-shut-
down feature to effectively operate. Place the n-channel
MOSFET as close as possible to OUT.
When the MAX6399 junction temperature exceeds T
+150°C, the thermal sensor signals the shutdown logic,
turning off the GATE output, allowing the device to cool.
The thermal sensor turns GATE on after the IC’s junc-
tion temperature cools by 20°C. For continuous opera-
tion, do not exceed the absolute maximum junction-
temperature rating of T
Figure 6. Input Overvoltage Protection Configuration
IN
IN
SET
MAX6399
GATE
GND
J
= +160°C.
Thermal Shutdown
OUT
TO DC-DC
CONTROLLER
INPUT
J
=