PM6685 datasheet(30/52 Pages) STMICROELECTRONICS

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Device description

PM6685

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V5SW pin allows to keep the 5V linear regulator always active or to enable the internal

bootstrap-switch over function: if the 5V switching output is connected to V5SW, when the

voltage on V5SW pin is above 4.8V, an internal 3.0

Ω max p-channel MOSFET switch

connects V5SW pin to LDO5 pin and simultaneously LDO5 shuts down. This configuration

allows to achieve higher efficiency. V5SW can be connected also to an external 5V supply.

LDO5 regulator turns off and LDO5 is supplied externally. If V5SW is connected to ground,

the internal 5V regulator is always on and supplies LDO5 output.

The 3.3V linear regulator is supplied by LDO5 output.

LDO3_SEL pin allows to keep 3.3V linear regulator always enabled, always disabled or to

enable the internal bootstrap-switch over function. According to Table 7:

●

If LDO3_SEL is connected to VREF pin, when the power good signal of the 3.3V

switching output voltage PGOOD3(see related sections) is high, the internal linear

regulator is turned off and LDO3 output is connected directly to OUT3 pin through an

internal 3

Ω max p-channel MOSFET switch.

●

If LDO3_SEL is connected to 5V, the internal 3.3V regulator is always on and supplies

LDO3 output.

●

If LDO3_SEL is connected to ground, the internal 3.3V regulator is always off and

LDO3 output is clamped to ground.

7.11

Power up sequencing and operative modes

Let’s consider SHDN, EN5 and EN3 low at the beginning. The battery voltage is applied as

input voltage. The device is in shutdown mode.

When the SHDN pin voltage is above the shutdown device on threshold(1.5V typ.), the

controller begins the power-up sequence. All the latched faults are cleared. LDO5

undervoltage control is blanked for 4 ms and the internal regulator LDO5 turns on. If the

LDO5 output is above the UVLO threshold after this time, the device enters in standby

mode. The switching outputs are kept to ground by turning on the low side MOSFETs.

Table 7.

V5SW multifunction pin

V5SW

Description

GND

The 5V linear regulator is always turned on and supplies LDO5 output.

Switching 5V

output

The 5V linear regulator is turned off when the voltage on V5SW is above 4.8V

and LDO5 output is supplied by the switching 5V output.

External 5V

supply

The 5V linear regulator is turned off when the voltage on V5SW is above 4.8V

and LDO5 output is supplied by the external 5V.

Table 8.

LDO3_SEL multifunction pin

LDO3_SEL

Description

GND

The 3.3V linear regulator is always turned off.

VREF

The 3.3V linear regulator is turned off when PGOOD3 is high. LDO3 output is

supplied by the switching 3.3V output.

LDO5

The 3.3V linear regulator is always turned on and supplies LDO3 output.

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