STGAP1AS datasheet(33/70 Pages) STMICROELECTRONICS

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STGAP1AS

Functional description

7.8

SENSE overcurrent protection

This function is suitable in applications in which it is possible to measure the load current

through the use of a shunt resistor, or in applications that use IGBTs with the current sense

pin available. The load current (or a fraction of it in case SenseFETs are used) is converted

to voltage by an external shunt resistor and is fed to the SENSE pin (comparator input).

When an overcurrent event occurs the sense voltage reaches the VSENSEth threshold, the

device is forced in “safe state” and the SENSE status flag is forced high and latched.

The VSENSEth threshold is programmable through the SPI (refer to Section 9.2.2 on page

7.9

Miller clamp function

The Miller clamp function allows the control of the Miller current during the power stage

switching in half-bridge configurations. When the external power transistor is in the OFF

state, the driver operates to avoid the induced turn-on phenomenon that may occur when

the other switch in the same leg is being turned on, due to the Cgc capacitance.

During the turn-off period the gate of the external switch is monitored through the CLAMP

pin.

The CLAMP switch is activated when gate voltage goes below the voltage threshold

VCLAMPth, thus creating a low impedance path between the switch gate and the VL pin.

This function can be disabled setting low the CLAMP_EN bit in the CFG5 register (high by

default).

7.10

2-level turn-off function

If an overcurrent event happens, a large voltage overshoot exceeding VCE absolute ratings

may occur across the power switch during the turn-off, due to the parasitic stray

inductances.

The 2-level turn-off function (2LTO) allows the reduction of the stressing overvoltage

experienced by the power component in overcurrent condition by switching off the external

power in two phases.

In the first phase the GOFF voltage is actively forced to a programmable value V2LTOth; after

a programmable delay t2LTOtime the GOFF is forced to VL to complete the gate turn-off.

This allows to slow down the critical part of the turn-off transient, that may induce the

overvoltage spikes.

The voltage level V2LTOth and duration t2LTOtime of the intermediate off-level are

programmable through the SPI.

It is possible to program when this feature takes place, refer to the following paragraphs.

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