MP2321 – 19V, 2A, LOW IQ, STEP-DOWN CONVERTER

MP2321 Rev. 1.1

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10

5/24/2019

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PIN FUNCTIONS

Package

Pin #

Name

Description

1, 12

GND

System ground. GND is the reference ground for the regulated output voltage. GND

requires special consideration during PCB layout.

2, 13

SW

Switch output. Connect SW using wide PCB traces.

3, 14

VIN

Supply voltage. The MP2321 operates from a 4V to 19V input rail. A capacitor (C1) is

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

connection.

4

FREQ/MODE

Frequency set during CCM operation. Connect a resistor to VIN to set the switching

frequency and operate the MP2321 in forced PWM mode. Connect a resistor to GND to

set the switching frequency and operate the MP2321 in auto PFM/PWM mode. Do not

float FREQ/MODE.

5

PG

Power good output. The output of PG is an open drain that goes high if the FB voltage

is within 90% to 110% of VREF. There is a 140µs delay when PG goes high.

Note: If PG is pulled up to an external voltage, PG will not de-assert (Logic low) if EN is

low or if input power is off. It is recommended that PG is pulled up to VCC pin and in

this case PG will de-assert (Logic low) when EN is Low or if input power is off. Refer to

Applications section for additional details.

6

SS

Soft start. Connect a capacitor across SS and GND to set the soft-start time to avoid

start-up inrush current.

7

FB

Feedback. FB sets the output voltage when connected to the tap of an external resistor

divider connected between the output and GND.

8

CR

Internal ramp adjust. Connect a capacitor from VOUT to CR to adjust the internal ramp

amplitude. This can be used to improve transient performance.

9

EN

Enable. Set EN = 1 to enable the MP2321. For automatic start-up, connect EN to VIN

with a pull-up resistor.

10

BST

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

the high-side switch driver.

11

VCC

Internal bias supply. VCC is an internal 5V LDO output. Decouple VCC with a 1µF

ceramic capacitor placed as close to VCC as possible.