AN2002

Using the Demoboard for the TD350 Advanced IGBT Driver

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timing. The level can be easily set by an external Zener diode D1, and its value is chosen depending on

the IGBT characteristics. This 2-level turn-off sequence takes place at each cycle, it has no effect if the

current doesn’t exceed the normal maximum rated value, but protects the IGBT in case of overcurrent

(with a slight increase of conduction losses).

In the demoboard original configuration, Ta (duration of the intermediate level) is set to approximately

1.5µs by R8=4K7 and C4=470pF. The intermediate level is set by 10V Zener diode D1 and bleeding

resistor R11=10K.

Tip:

How can you inhibit 2-level turn-off?

Connect LVOFF to VH by replacing R10 by a short-circuit, remove C4 capacitor and keep

COFF pin connected to Vref by R8=4K7.

2.5 Desaturation protection feature

The desaturation function provides a protection against overcurrent events. Voltage across the IGBT is

an internal 250mA current source and an external capacitor C1. The DESAT pin is connected to output

demoboard connector by R1 resistor. In order to implement the desaturation feature, an external high

voltage diode (1kV or more) should be connected between the IGBT collector and the demoboard output

connector pin 1 (see Figure 6 for reference schematic).

The high voltage diode blocks the high voltage during IGBT off state. This diode doesn’t need to be fast,

a standard 1kV (or more) diode is acceptable.

During operation, the DESAT capacitor is discharged when TD350 output is low (IGBT off). When the

IGBT is turned on, the DESAT capacitor starts charging and desaturation protection is effective after the

With the capacitor used in the demoboard (C1=100pF), the blanking time value will be close to 3ms.

Tip:

What should one do with the DESAT pin when it isn’t used?

Connect DESAT to GND by shorting together pin 1 and pin 3 on the demoboard output

connector (see Figure 5).

t

b

7.2V

C

1

250

µA

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