MP4431

– 36V, 1A, LOW IQ, SYNC, STEP-DOWN CONVERTER

MP4431 Rev. 1.01

www.MonolithicPower.com

13

1/12/2018

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PIN FUNCTIONS

Pin #

Name

Description

1

PHASE

Selectable in-phase or 180°out-of-phase of SYNC input. Drive PHASE high to be

in-phase. Drive PHASE low to be 180°out-of-phase.

2

VIN

Input supply. VIN supplies power to all of the internal control circuitries and the

power switch connected to SW. A decoupling capacitor to ground must be placed

close to VIN to minimize switching spikes.

3, 10

SW

Switch node. SW is the output of the internal power switch.

4, 9

PGND

Power ground. PGND is the reference ground of the power device and requires

careful consideration during PCB layout. For best results, connect PGND with copper

pours and vias.

5

EN

Enable. Pull EN below the specified threshold to shut the chip down. Pull EN above

the specified threshold to enable the chip.

6

SYNC

Synchronize. Apply a 350kHz to 2.5MHz clock signal to SYNC to synchronize the

internal oscillator frequency to the external clock. The external clock should be at

forced continuous conduction mode (CCM) or advanced asynchronous mode (AAM).

Drive SYNC high before the chip starts up to choose forced CCM. Drive SYNC low or

leave SYNC floating to choose AAM.

7

PG

Power good indicator. The output of PG is an open drain and goes high if the output

voltage is within ±10% of the nominal voltage.

8

BIAS

External power supply for the internal regulator. Connect BIAS to an external

power supply (5V

≤ V

Float BIAS or connect BIAS to ground if not used.

11

BST

Bootstrap. BST is the positive power supply for the high-side MOSFET driver

connected to SW. Connect a bypass capacitor between BST and SW.

12

VCC

Internal bias supply. VCC supplies power to the internal control circuit and gate

drivers. A

≥1µF decoupling capacitor to ground is required close to VCC.

13

AGND

Analog ground. AGND is the reference ground of the logic circuit.

14

SS

Soft-start input. Place an external capacitor from SS to AGND to set the soft-start

period. The MP4431 sources 10µA from SS to the soft-start capacitor during start-up.

As the SS voltage rises, the feedback threshold voltage increases to limit inrush

current during start-up.

15

FB

Feedback input. Connect FB to the tap of an external resistor divider from the output

to AGND to set the output voltage. The feedback threshold voltage is 0.8V. Place the

resistor divider as close to FB as possible. Avoid placing vias on the FB traces.

16

FREQ

Switching frequency program. Connect a resistor from FREQ to ground to set the

switching frequency.