MP8757–18V, HIGH CURRENT SYNCHRONOUS BUCK CONVERTER

MP8757 Rev. 1.0

www.MonolithicPower.com

6

5/1/2018

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PIN FUNCTIONS

PIN #

Name

Description

1

BST

Bootstrap. A capacitor connected between SW and BST pins is required to form a

floating supply across the high-side switch driver.

2, 3

SW

Switch Output. Connect this pin to the inductor and bootstrap capacitor. This pin is

driven up to the VIN voltage by the high-side switch during the on-time of the PWM

duty cycle. The inductor current drives the SW pin negative during the off-time. The on-

resistance of the low-side switch and the internal diode fixes the negative voltage. Use

wide and short PCB traces to make the connection. Try to minimize the area of the SW

pattern.

4

NC

Not Connected.

5, 6

VOUT

Buck regulator output voltage sense. Connect this pin to the output capacitor of the

regulator directly

7

NC

Not Connected.

8

AGND

Analog ground. The internal reference is referred to AGND. Connect the GND of the

FB divider resistor to AGND for better load regulation.

9

NC

Not Connected.

10,11

Exposed

Pad 20,21

PGND

Power Ground. Use wide PCB traces and multiple vias to make the connection.

12

Exposed

Pad 19

VIN

Supply Voltage. The VIN pin supplies power for internal MOSFET and regulator. The

MP8757 operates from a +5V to +18V input rail. An input capacitor is needed to

decouple the input rail. Use wide PCB traces and multiple vias to make the connection.

13

PG

Power good output, the output of this pin is an open drain signal and is high if the

output voltage is higher than 95% of the nominal volta

ge. There is a delay from FB ≥

95% to PG goes high.

14

FB

Feedback. An external resistor divider from the output to GND, tapped to the FB pin,

sets the output voltage. Place the resistor divider as close to FB pin as possible. Avoid

vias on the FB traces.

15

GND

Ground pin. This pin needs to be connected to either PGND or AGND for normal

operation.

16

VCC

Internal 5V LDO output. The driver and control circuits are powered from this voltage.

Decouple with a minimum 1µF ceramic capacitor as close to the pin as possible. X7R

or X5R grade dielectric ceramic capacitors are recommended for their stable

temperature characteristics.

17

EN

Enable. EN is a digital input, which are used to enable or disable the regulators. Once

EN=1, the regulator output will be turned on; when EN=0, the regulator will be turned

off.

18

NC

Not connected.