MAX5902(2002) 查看數據表（PDF） - Maxim Integrated
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MAX5902 Datasheet PDF : 11 Pages
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+72V SOT23 Simple Swapper Hot-Swap
Controllers
+24V
OPTIONAL
ON/OFF
DGND
GND
HOT-SWAP CONTROLLER
R2
40.2kΩ
R1
3.01kΩ
MAX5902
MAX5903
VS
ON/OFF
GND
Figure 3. Programmed +18V Lockout, with Optional Optocoupler
On/Off Control.
A thermal shutdown feature protects the external MOS-
FET by turning it off if the die temperature of the
MAX5902/MAX5903 exceeds +125°C. The MAX5902/
MAX5903 must be in good thermal contact with the
external MOSFET. See Layout Guidelines in the Appli-
cations section of the data sheet.
A circuit breaker function monitors the voltage across
the external MOSFET, VSD, and turns off the MOSFET if
VSD exceeds the circuit breaker threshold, VCB. The
circuit breaker function is enabled after the MOSFET is
fully enhanced. Three threshold voltage options are
available—300mV, 400mV, and 500mV. One version is
available with no circuit breaker function. Fault man-
agement for the MAX5902/MAX5903 is offered with two
different configurations; latched and automatic retry.
Latched Circuit Breaker
After a circuit breaker trip event the latched
versions (MAX5902L/MAX5903L) drive GATE to
VS, turning off the external MOSFET, and PGOOD
(PGOOD) is deasserted. A latched off condition
needs to be reset by toggling ON/OFF low for at
least 10ms, or by cycling the power supply, VS.
Automatic Retry Circuit Breaker
After a circuit breaker trip event the automatic retry
versions (MAX5902A/MAX5903A) drive GATE to VS,
turning off the external MOSFET, and PGOOD
(PGOOD) is deasserted. If the start conditions are met
for a full 150ms (tRS) the start sequence is re-initiated.
The start conditions are: the device is not in UVLO;
ON/OFF is not driven low; and the device is not in ther-
mal shutdown.
No Circuit Breaker
For the versions without a circuit breaker, MAX5902N
(MAX5903N), PGOOD (PGOOD) are asserted when the
MOSFET is fully enhanced. Once powered up the
MAX5902N/MAX5903N ignore the MOSFET drain-to-
source voltage for applications where a circuit breaker
function is not desired.
Applications Information
ON/OFF Control Input
The ON/OFF control input provides three functions:
external ON/OFF control; setting of the UVLO level; and
resetting after a circuit breaker event has caused the
MAX5902L/MAX5903L to turn off the external MOSFET.
Pulling ON/OFF to GND for at least 10ms (tOFF) forces
the MAX5902/MAX5903 to turn off the external MOSFET
(see Figure 3 for a circuit example). To reset the
MAX5902L/MAX5903L after a circuit breaker event, tog-
gle ON/OFF to GND for at least 10ms (tOFF).
ON/OFF can be used to sequence power supplies.
Connecting a capacitor from ON/OFF to GND will delay
the rise of ON/OFF proportional to the capacitance and
input impedance of ON/OFF, typically 33kΩ (Figure 4).
The MAX5902/MAX5903 can be controlled by logic
level signals. Logic level signals of 3.3V or 1.8V may be
directly connected to ON/OFF. For 5V logic level control,
insert a series 47kΩ resistor as shown in Figure 5.
HOT-SWAP CONTROLLER #1
VS
MAX5902
MAX5903
VS
ON/OFF
C
GND
HOT-SWAP CONTROLLER #2
MAX5902
VS MAX5903
ON/OFF
2C
GND
GND
Figure 4. Power-Supply Sequencing
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