L6591 datasheet(6/32 Pages) STMICROELECTRONICS

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Pin settings

L6591

6/32

Pin N.

Name

Function

9Vcc

Supply voltage of both the signal part of the IC and the low-side gate driver.

The internal high voltage generator charges an electrolytic capacitor

connected between this pin and GND (#11) as long as the voltage on the

pin is below the start-up threshold of the IC, after that it is disabled and the

chip turns on. Sometimes a small bypass capacitor (0.1 µF typ.) to GND

might be useful to get a clean bias voltage for the signal part of the IC. The

minimum operating voltage (UVLO) is adapted to the loading conditions of

the converter to ease burst-mode operation, during which the available

supply voltage for the IC drops.

LVG

Low-side gate-drive output. The driver is capable of 0.3 A min. source and

0.8A min. sink peak current to drive the gate of the lower MOSFET of the

half-bridge leg. The pin is actively pulled to GND (#11) during UVLO.

GND

Chip ground. Current return for both the low-side gate-drive current and the

bias current of the IC. All of the ground connections of the bias components

should be tied to a track going to this pin and kept separate from any pulsed

current return.

N.C.

High-voltage spacer. The pin is not connected internally to isolate the group

of high-voltage pins and comply with safety regulations (creepage distance)

on the PCB.

FGND

High-side gate-drive floating ground. Current return for the high-side gate-

drive current. Layout carefully the connection of this pin to avoid too large

spikes below ground.

HVG

High-side floating gate-drive output. The driver is capable of 0.3 A min.

source and 0.8 A min. sink peak current to drive the gate of the upper

MOSFET of the half-bridge leg. A pull-down resistor between this pin and

pin 13 (FGND) makes sure that the gate is never floating during UVLO.

BOOT

High-side gate-drive floating supply voltage. The bootstrap capacitor

connected between this pin and pin 13 (FGND) is fed by an internal

synchronous bootstrap diode driven in-phase with the low-side gate-drive.

This patented structure can replace the normally used external diode.

HVSTART

High-voltage start-up. The pin is to be connected directly to the rectified

mains voltage. A 0.8 mA internal current source charges the capacitor

connected between pin Vcc (#9) and GND (#11) until the voltage on the Vcc

pin reaches the start-up threshold. Normally it is re-enabled when the

voltage on the Vcc pin falls below 5 V, except under latched shutdown

conditions, in which case it is re-enabled as the Vcc voltage falls 1 V below

the start-up threshold to keep the latch active.

Table 1.

Pin functions (continued)

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