MAX6399 MAXIM [Maxim Integrated Products], MAX6399 Datasheet - Page 5

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

Figure 1. Functional Diagram
PIN
—
1
2
3
4
5
6
7
8
SET
OUT_SET
5V
OUT_SET
0.5V
NAME
SHDN
GATE
GND
POK
OUT
SET
EP
IN
IN
1.23V
High-Voltage, Overvoltage/Undervoltage,
_______________________________________________________________________________________
UVLO
Supply Voltage Input. Bypass with a 10µF capacitor (minimum).
Shutdown Input. Drive SHDN low to force GATE low, turning off the external n-channel MOSFET. SHDN is
internally pulled down to GND with a 1µA current source. Toggle SHDN to unlatch GATE after an
overvoltage condition. Connect to IN for normal operation.
Overvoltage Threshold Adjustment Input. Use SET to monitor a system output voltage. Connect SET to an
external resistor voltage-divider network to adjust the desired overvoltage limit threshold. GATE is quickly
turned off when SET rises above its 0.5V (typ) threshold.
Power-OK Open-Drain Output. POK asserts low when OUT_SET falls below its 1.23V (typ) threshold.
Ground
Gate-Drive Output. Connect GATE to the gate of an external n-channel FET. GATE is a charge pump with a
100µA pullup current to IN + 10V (typ) during normal operation. GATE is quickly turned off during an
overvoltage condition. GATE remains latched off until the power is recycled or SHDN is toggled. GATE pulls
low when SHDN is low.
Output Voltage-Sense Input. Connect to the source of the external n-channel MOSFET.
Undervoltage Detector Input. Use OUT_SET to monitor the source of the MOSFET. Connect a
resistor-divider from OUT to OUT_SET to adjust the desired undervoltage threshold. POK asserts low
when OUT_SET falls below its 1.23V threshold.
Exposed Pad. Connect to ground plane.
MAX6399
CHARGE
PUMP
PROTECTION
THERMAL
SHDN
GATE
Protection Switch Controller
GND
OUT
POK
The MAX6399 is an ultra-small, low-current protection
circuit utilized in DC-DC converter applications. The
MAX6399 monitors the input and output voltages of a
DC-DC converter for undervoltage and overvoltage
conditions. The MAX6399 controls an external n-chan-
nel MOSFET to isolate the load during an overvoltage
condition. The device allows system designers to size
the external n-channel MOSFET to their load current
and board size.
The MAX6399 drives the MOSFET’s gate high when the
monitored DC-DC output voltage is below the program-
mable overvoltage threshold, programmed through
SET. An internal charge-pump circuit provides a guar-
anteed 10V gate-to-source drive to ensure low input-to-
load voltage drops in normal operating modes. When
the monitored DC-DC output voltage rises above the
user-adjusted overvoltage threshold, GATE latches low,
turning off the MOSFET. The MOSFET remains off until
the power is recycled or by toggling SHDN.
The MAX6399 also monitors for an undervoltage condi-
tion at the input of the DC-DC converter through
OUT_SET. An active-high, open-drain, power-good out-
put can be used to drive the EN input, notifying the sys-
tem when the monitored voltage is below the adjusted
undervoltage voltage threshold.
FUNCTION
Detailed Description
Pin Description
5