Device description

PM6644

20/35

Doc ID 023203 Rev 1

2.1.11

VCC and BYP power management

VCC supplies both the controller and the drivers of the integrated high-side and low-side

MOSFETs. An integrated 3.8 V generator from the VIN pin provides the voltage to the VCC

pin.

The PM6644 provides a switch-over function that allows the turning-off of the 3.8 V

generator when a voltage is applied at the BYP pin. If the voltage at the BYP pin is higher

than 3.2 V, the internal generator is turned off and the VCC pin is connected with an internal

switch (16

Ω typ.) to the BYP pin. This feature decreases the power dissipation of the device.

If BYP < 2.4 V, the internal switch is turned off and the VCC output is supplied with the 3.8 V

generator.

2.1.12

3.3 V linear regulator section (REF3)

The PM6644 has an integrated linear regulator (REF3) that can provide a maximum RMS

current of 5 mA. The input of the linear regulator is the BYP pin. The linear regulator is

turned on when BYP > 3.2 V. Connect pin REF3 with a 100 nF ceramic capacitor to GND.

2.1.13

General fault management: thermal protection

If the internal temperature of the device exceeds typically +150 °C, the controller shuts down

immediately all the internal circuitry. The switching section performs the soft-end

management. Toggling EN or cycling VCC < 2.1 V and then VCC > 3 V, resets the latched

fault.

Table 9.

VCC and BYP management (EN pin > 2 V)

BYP

VIN

VCC

5 V generator

Switch-over

resistance

< 2.4 V

< 6 V

Enabled

< 2.4 V

3.8 V

Enabled

> 3.2 V

BYP

Disabled

16

Ω