PM6680 datasheet(30/49 Pages) STMICROELECTRONICS

30 / 49 page

Device description

PM6680

30/49

7.10

Internal linear regulator

The PM6680 has an internal linear regulator providing 5V (LDO5) at ±2% accuracy. High

side drivers, low side drivers and most of internal circuitry are supplied by LDO5 output

through VCC pin (an external RC filter may be applied between LDO5 and VCC). The linear

regulator can provide an average output current of 50mA and a peak output current of

100mA. Bypass LDO5 output with a minimum 1

µF ceramic capacitor and a 4,7µF tantalum

capacitor ( ESR 2

Ω). If the 5V output goes below 4V, the system detects a fault condition

and all the circuitry is turned off. A power on reset or a toggle on SHDN pin is necessary to

restart the device.

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.

7.11

Power up sequencing and operative modes

Let's consider SHDN, EN1 and EN2 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.

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

sequence.

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.

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.

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