MP8768 – 8A, 28V, SYNCHRONOUS STEP-DOWN CONVERTER WITH INTERNAL MOSFET

MP8768 Rev. 1.0

www.MonolithicPower.com

3

12/12/2013

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Parameters

Symbol

Condition

Min

Typ

Max

Units

Power Good Delay

20

μs

Power Good Sink Current

Capability

Sink 4mA

0.4

V

Power Good Leakage Current

10

nA

Under Voltage Lockout Threshold

Rising

3.9

4.1

4.3

V

Under Voltage Lockout Threshold

Hysteresis

880

mV

VCC Regulator

4.5

5

V

VCC Load Regulation

Icc=20mA

5

%

Gate Drive Sink Impedance

(4)

1

Ω

Gate Drive Source Impedance

(4)

4

Ω

Thermal Shutdown

150

°C

Note:

4) Guaranteed by design.

PIN FUNCTIONS

Pin #

Name

Description

1

FB

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

sets the output voltage. To prevent current limit run away during a short circuit fault

condition the frequency fold-back comparator lowers the oscillator frequency when

the FB voltage is below 400mV.

2

PG

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

voltage is lower than 10% of the nominal voltage. There is a 20µs delay to pull PG if

the output voltage is lower than 10% of regulation value.

3

EN/SYNC

EN=1 to enable the MP8768. External clock can be applied to EN pin for changing

switching frequency. For automatic start-up, connect EN pin to VIN with 100KΩ

resistor.

4,5,6

IN

Supply Voltage. The MP8768 operates from a +4.5V to +28V input rail. C1 is needed

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

connection.

7

AAM

Tie to ground forces the MP8768 in synchronous Mode. Tie to a voltage set by a

resistor divider forces the MP8768 into non-synchronous mode when load is small.

8,9,10

SW

Switch Output. Use wide PCB traces and multiple vias to make the connection.

11

BST

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

floating supply across the high-side switch driver.

12

VCC

Bias Supply. Decouple with 1µF capacitor.

13

BG

Low Side Gate Drive output.

14

GND

Exposed Pad

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

this reason care must be taken in PCB layout.

Connect exposed pad to GND plane for optimal thermal performance.