PM6680A datasheet(28/48 Pages) STMICROELECTRONICS

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Device description

PM6680A

28/48

7.11

Power up sequencing and operative modes

Let us consider SHDN, EN1 and EN2 low at the beginning. An external voltage is applied as

input voltage. The device is in shutdown mode.

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

When EN1 and EN2 pins are forced high the switching sections begin their soft start

sequence.

Table 8.

Operatives modes

Mode

Conditions

Description

Run

SHDN is high,

EN1/EN2 pins are high

Switching regulators are enabled; internal linear

regulators outputs are enabled.

Standby

Both EN1/EN2 pins are low

and SHDN pin is high

Internal Linear regulators active (LDO5 is always on).

In Standby mode LGATE1/LGATE2 pins are forced

high while HGATE1/HGATE2 pins are forced low.

Shutdown

SHDN is low

All circuits off.

PM6680A 数据表(PDF) 28 Page - STMicroelectronics