MP8794

– 16V, 20A, SYNCHRONOUS STEP-DOWN CONVERTER

MP8794 Rev. 1.0

www.MonolithicPower.com

4

12/2/2019

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© 2019 MPS. All Rights Reserved.

PIN FUNCTIONS

Pin #

Name

Description

1

BST

Bootstrap. Connect a capacitor between SW and BST to form a floating supply across

the high-side switch driver.

2

AGND

Analog ground. Select AGND as the control circuit reference point.

3

CS

Current limit. Connect a resistor to AGND to set the current limit trip point.

4

MODE

Operation mode selection. Program MODE to select the operating switching frequency.

See Table 1 on page 14 for additional details.

5

REF/TRK

External tracking voltage input. Decouple REF/TRK by placing a ceramic capacitor as

close to the pin as possible. X7R or X5R grade dielectric ceramic capacitors are

recommended for their stable temperature characteristics. The capacitance of the

capacitor determines the soft-start time. See Equation 2 on page 14 for additional details.

6

VSNS-

Differential remote-sense negative input. Connect VSNS- directly to the negative side

of the voltage sense point. Short VSNS- to GND if the remote sense is not used.

7

FB

Feedback (differential remote-sense positive input). An external resistor divider from

the output to VSNS-, tapped to FB, sets the output voltage. It is recommended to place

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

8

EN

Enable. EN is an input signal that turns the regulator on or off. Drive EN high to turn the

regulator on; drive EN low to turn it off. For automatic start-up, connect EN to VIN through

a pull-up resistor or a resistive voltage divider. Do not float EN.

9

PGOOD

Power good output. PGOOD is an open-drain signal. A pull-up resistor connected to a

DC voltage is required to indicate a logic high signal if the output voltage is within

regulation. There is a delay of about 0.9ms between the time FB becomes greater than or

equal to 92.5% of the REF and the time PGOOD pulls high.

10, 21

VIN

Input voltage. VIN supplies power to the internal MOSFET and regulator. Input

capacitors are required to decouple the input rail. Use wide PCB traces to make the

connection.

11

–18

PGND

System ground. PGND is the reference ground of the regulated output voltage, and

requires careful consideration while designing the PCB layout. Use wide PCB traces to

make the connection.

19

VCC

Internal 3V LDO output. The driver and control circuits are powered by the VCC

pin’s

voltage. Decouple VCC with a minimum 1µF ceramic capacitor, placed as close to the pin

as possible. X7R or X5R grade dielectric ceramic capacitors are recommended for their

stable temperature characteristics.

20

SW

Switch output. Connect SW to the inductor and bootstrap capacitor. SW is driven up to

VIN by the high-side switch during the on time of the PWM duty cycle. The inductor

current drives SW low during the off time. Use wide PCB traces to make the connection.