5

Functional description

5.1

Gate driving power supply and UVLO

The STGAP2S is a flexible and compact gate driver with 4 A output current and rail-to-rail outputs. The device

allows implementation of either unipolar or bipolar gate driving.

I

S

O

L

A

T

I

O

N

VH

GOFF

GNDISO

VDD

GND

IN+

IN-

GON

+

VH

+

VH

+

VL

I

S

O

L

A

T

I

O

N

VH

GOFF

GNDISO

VDD

GND

IN+

IN-

GON

Unipolar gate driving

Bipolar gate driving

1uF

100nF

1uF

100nF

1uF

100nF

100nF

1uF

1uF

Undervoltage protection is available on VH supply pin. A fixed hysteresis sets the turn-off threshold, thus avoiding

intermittent operation.

pins status.

The VDD and VH supply pins must be properly filtered with local bypass capacitors. The use of capacitors with

different values in parallel provides both local storage for impulsive current supply and high-frequency filtering.

The best filtering is obtained by using low-ESR SMT ceramic capacitors, which are therefore recommended. A

100 nF ceramic capacitor must be placed as close as possible to each supply pin, and a second bypass capacitor

with value in the range between 1 µF and 10 µF should be placed close to it.

5.2

Power up, power down and 'safe state'

The following conditions define the “safe state”:

•

GOFF = ON state

•

GON = high impedance

•

CLAMP = ON state (for STGAP2SC)

The device integrates a structure which clamps the driver output to a voltage not higher than SafeClp when VH

voltage is not high enough to actively turn the internal GOFF MOSFET on. If VH positive supply pin is floating or

not supplied the GOFF pin is therefore clamped to a voltage smaller than SafeClp.

If the supply voltage VDD of the control section of the device is not supplied, the output is put in safestate, and

remains in such condition until the VDD voltage returns within operative conditions.

After power-up of both isolated and low voltage side the device output state depends on the input pins' status.

STGAP2S

Functional description

DS12541 - Rev 3

page 8/23