AN4043 datasheet(27/60 Pages) STMICROELECTRONICS

27 / 60 page

AN4043

Electrical characteristics and functions

Doc ID 022726 Rev 2

27/60

Both solutions allow to detect the total current in all three phases of the inverter. The filter is

based on the RSF and CSF network and its time constant is given by:

Equation 5

In addition to the RC time constant, the turn-off propagation delay of the gate driver, tisd

(specified in the datasheet) and the IGBT turn-off time (in the range of tens of ns), must be

considered in the total delay time (tTotal), which is the time necessary to completely switch

off the IGBT once the short-circuit event is detected. Therefore, the tTotal is calculated as

follows:

Equation 6

and the tSF is recommended to be set in the range of 1~2 µs.

In the case of a 3-shunt resistor circuit, a specific control technique can be implemented by

using the three shunt resistors (RSHUNT_U, RSHUNT_V and RSHUNT_W) able to monitor each

phase current.

An example of a short-circuit event is shown in

Figure 17, where it is possible to note the

very fast protection, thanks to the smart shutdown function, against fault events. The main

steps are:

●

t1: collector current IC starts to rise. SC event is not detected yet due to the RC

network on the CIN pin.

●

t2: voltage on VCIN reaches the VREF. SC event is detected and the smart shutdown

starts to turn off the SLLIMM-nano.

●

t3: the SD in activated.

●

t4: the SLLIMM-nano is definitively turned off in 580 ns (including the td(off) time of

IGBT) from SC detection.

Finally, the total disable time is t4-t2 and the total SC action time is t4-t1.

⋅

off

isd

Total

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