MPM3530

– 55V, 3A, STEP-DOWN POWER MODULE

MPM3530 Rev. 1.0

www.MonolithicPower.com

13

9/21/2018

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active, the MPM3530 is powered on when the

input voltage is higher than the UVLO rising

threshold. The MPM3530 is powered off when

the input voltage drops below the UVLO falling

threshold.

Thermal Shutdown Protection

Thermal

shutdown

is

employed

in

the

MPM3530

by

monitoring

the

temperature

internally. If the junction temperature exceeds

the threshold (typically 170°C), the regulator

shuts off. The regulator turns on again when the

temperature drops below 160°C. There is a

hysteresis of ~10°C.

Power Good (PG)

The MPM3530 has one power good (PG) pin

out to indicate normal operation after a soft-

start time. PG is the open drain of an internal

MOSFET and should be connected to VDD or

an external voltage source through a resistor

(i.e.: 100k

Ω). After the input voltage is applied,

the MOSFET is turned on, and PG is pulled to

to GND to indicate a failure output status.

Floating Driver and Bootstrap Charging

An internal bootstrap capacitor (typically

0.1μF)

between BST and SW powers the floating

power MOSFET driver. This floating driver has

its own UVLO protection. This UVLO’s rising

threshold is 2.3V with a hysteresis of 300mV.

The driver’s UVLO is soft-start related. When

the

bootstrap

voltage

reaches

its

UVLO

threshold, the soft-start circuit resets. When the

bootstrap UVLO is gone, the reset is off, and

the soft-start process resumes.

The

dedicated

internal

bootstrap

regulator

regulates and charges the bootstrap capacitor

to 4.2V. When the voltage between the BST

and SW nodes is less than its regulation, a

PMOS pass transistor from VIN to BST turns on.

The charging current path is from VIN to BST to

SW.

the bootstrap capacitor can be charged. When

capacitor cannot be charged. When the LS-FET

its largest, making it the best period to charge.

can charge the bootstrap capacitor. At higher

duty cycles, there is less time for the bootstrap

charging, so the bootstrap capacitor may not be

charged sufficiently. If the internal circuit does

not have sufficient voltage and the bootstrap

capacitor is not charged, extra external circuitry

can be used to ensure that the bootstrap

voltage is within the normal operating region.