MP8764 ― 12A, 18V, SYNCHRONOUS STEP-DOWN CONVERTER WITH LATCH-OFF OCP

MP8764 Rev. 1.2

www.MonolithicPower.com

5

6/21/2016

MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.

© 2016 MPS. All Rights Reserved.

PIN FUNCTIONS

PIN#

16-Pin

QFN

Name

Description

1

EN

Enable pin. EN is a digital input that turns the regulator on or off. Drive EN high to

turn on the regulator, drive it low to turn it off. Connect EN to IN through a pull-up

resistor or a resistive voltage divider for automatic startup. Do not float this pin. See

Enable Control section for more details.

2

FREQ

Frequency set during CCM operation. A resistor connected between FREQ and IN is

required to set the switching frequency. The ON time is determined by the input

voltage and the resistor connected to the FREQ pin. IN connect through a resistor is

used for line feed-forward and makes the frequency basically constant during input

voltage’s variation.

3

FB

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

sets the output voltage. It is recommended to place the resistor divider as close to FB

pin as possible. Vias should be avoided on the FB traces.

4

SS

Soft Start. Connect an external capacitor to program the soft start time for the switch

mode regulator.

5

AGND

Analog ground. Select this pin as the control circuit reference point.

6

PG

Power good output, the output of this pin is an open drain signal and a pull-up

resistor connected to a DC voltage is required to indicate high if the output voltage is

higher than 97% of the nominal voltage. There is a delay from FB ≥ 97% to PG goes

high.

7

VCC

Internal 4.8V 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.

8

BST

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

floating supply across the high-side switch driver.

9, 14

IN

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

MP8764 operates from a +2.5V to +18V input rail with 5V external bias and a +4.5V

to +18V input rail with internal bias. An input capacitor is needed to decouple the

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

10,11,12,1

3

PGND

System Ground. This pin is the reference ground of the regulated output voltage. For

this reason care must be taken in PCB layout. Use wide PCB traces to make the

connection.

15, 16

SW

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

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 Schottky diode fixes the

negative voltage. Use wide PCB traces to make the connection.