PM6685 datasheet(6/52 Pages) STMICROELECTRONICS

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Pin settings

PM6685

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2.2

Functions

Table 2.

Pin functions

Name

Description

SGND1

Signal ground. Reference for internal logic circuitry. It must be connected to the

signal ground plan of the power supply. The signal ground plan and the power

ground plan must be connected together in one point near the PGND pin.

COMP3

DC voltage error compensation pin for the 3.3V switching section.

FSEL

Frequency selection pin.

It provides a selectable switching frequency, allowing , allowing three different

values of switching frequencies for the 5V/3.3V switching sections.

4EN3

3.3V SMPS enable input.

– The 3.3V section is enabled applying a voltage greater than 2.4V to this pin.

– The 3.3V section is disabled applying a voltage lower than 0.8V.

When the section is disabled the High Side gate driver goes low and Low Side

gate driver goes high. If both EN3 and EN5 pins are low and SHDN pin is high

the device enters in standby mode.

SHDN

Shutdown control input.

– The device switch off if the SHDN voltage is lower than 0.8V (Shutdown

mode)

– The device switch on if the SHDN voltage is greater than 1.7V.

The SHDN pin can be connected to the battery through a voltage divider to

program an undervoltage lockout. In shutdown mode, the gate drivers of the two

switching sections are in high impedance (high-Z).

PGOOD

LDO3

Power Good signal for the 3.3V linear regulator. This pin is an open drain output.

It is shorted to GND if LDO3_SEL pin is at its low level or if the output voltage

on LDO3 pin is lower than 2.6V.

LDO3

3.3V Linear regulator output. LDO3 can provide 100mA peak current.

8OUT3

Output voltage sense for the 3.3V switching section.This pin must be directly

connected to the output voltage of the switching section.

9BOOT3

Bootstrap capacitor connection for the switching 3.3V section. It supplies the

high-side gate driver.

HGATE3

High-side gate driver output for the 3.3V section.

PHASE3

Switch node connection and return path for the high side driver for the 3.3V

section.

CSENSE3

Current sense input for the 3.3V section. This pin must be connected through a

resistor to the drain of the synchronous rectifier (RDSON sensing) to set the

current limit threshold.

LGATE3

Low-side gate driver output for the 3.3V section.

PGND

Power ground. This pin must be connected to the power ground plan of the

power supply.

LGATE5

Low-side gate driver output for the 5V section.

SGND2

Signal ground for analog circuitry. It must be connected to the signal ground

plan of the power supply.

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