MAX5902(2002) Ver la hoja de datos (PDF) - Maxim Integrated
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MAX5902 Datasheet PDF : 11 Pages
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+72V SOT23 Simple Swapper Hot-Swap
Controllers
5V LOGIC
GND
HOT-SWAP CONTROLLER
47kΩ
MAX5902
MAX5903
ON/OFF
GND
LOGIC CONTROL OF 3.3V OR LESS MAY BE CONNECTED
DIRECTLY TO THE MAX5902/MAX5903. FOR 5V LOGIC
CONTROL INSERT A SERIES 47kΩ RESISTOR AS SHOWN.
+9V TO +72V
GND
HOT-SWAP CONTROLLER
100kΩ
MAX5902
VS
ON/OFF
GND
Figure 5. Logic Control
Figure 6. Defeating Undervoltage Lockout
Turn-On and Turn-Off Delays
After power is applied, or ON/OFF is released, there is
a 150ms delay (tON) before the gate ramp is started.
This delay is also the automatic restart time delay.
In the event of a circuit breaker condition or an over-
temperature fault condition, the turn-off delay is less
than 4µs. An undervoltage condition must exist for at
least 10ms (tOFF) before the MAX5902/MAX5903 turns
off the external MOSFET. ON/OFF must be held low for
at least 10ms (tOFF) before the MAX5902/MAX5903
turns off the external MOSFET. Turn-off delay minimizes
spurious shutdowns due to noisy signals or momentary
voltage spikes, as well as preventing accidental reset-
ting of the circuit breaker latch (MAX5902L/MAX5903L).
Thermal Shutdown
A thermal shutdown feature helps protect the external
MOSFET. If the die temperature of the MAX5902/
MAX5903 exceeds +125°C, the MOSFET is turned off.
For accurate performance the MAX5902/MAX5903
must be in close thermal contact with the external MOS-
FET. See Layout Guidelines for information. Due to the
low power dissipation of the MAX5902/MAX5903, its
junction temperature will typically be within a few
degrees of the MOSFET. All versions of the MAX5902/
MAX5903 automatically restart from a temperature fault
when the junction temperature drops below +110°C.
Undervoltage Lockout
The MAX5902/MAX5903 turns off the external MOSFET
if the magnitude of the input voltage is below the level
set by ON/OFF for longer than 10ms (tOFF). If ON/OFF
is left unconnected, the lockout voltage (VUVLO)
defaults to 31.5V. VUVLO may also be set to any value
within the power-supply range by using external resis-
tors. To set the lockout voltage to a value between +9V
and +72V use a resistor divider connected between VS
and GND, with the center node of the divider connect-
ed to ON/OFF. For example, use a 3kΩ resistor (R1 in
Figure 3) from ON/OFF to GND and calculate the other
resistor, R2, using:
R2
=
R1
×
VUVLO
VON / OFF
− 1
where VUVLO is the desired lockout voltage, and
VON/OFF is the ON/OFF reference threshold specified in
the Electrical Characteristics table (typically 1.26V).
Figure 3 shows an example circuit with VUVLO set for
+18V. To defeat the UVLO simply connect a single
100kΩ resistor between ON/OFF and VS, as shown in
Figure 6.
The Power Good Output
The power good output, PGOOD (PGOOD), is open-
drain and asserts when the external MOSFET is fully
enhanced and VSD is less than the circuit breaker
threshold (VCB). For versions without the circuit breaker
function (MAX5902N/MAX5903N), PGOOD (PGOOD)
asserts when the external MOSFET is fully enhanced.
PGOOD (PGOOD) deasserts within 4µs when a circuit
breaker event occurs or if the die temperature exceeds
+125°C. PGOOD (PGOOD) deasserts if VS < VUVLO for
longer than 10ms or ON/OFF is held low for longer than
10ms.
The MAX5902 PGOOD is active-low and the MAX5903
PGOOD is active-high. Both are open-drain N-channel
MOSFETs with their sources connected to GND, and
can withstand up to +72V.
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