TD352 データシートの表示（PDF） - STMicroelectronics

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TD352

Advanced IGBT/MOSFET Driver

STMicroelectronics 

Functional description

5

Functional description

TD352

5.1

Input stage

The TD352 IN input is internally clamped at about 5 V to 7 V. The input is triggered by the

signal edge. When using an open collector optocoupler, the resistive pull-up resistor can be

connected to either VREF or VH.

Recommended pull-up resistor value with VH=16 V is from 4.7 kΩ to 22 kΩ.

5.2

Voltage reference

A voltage reference is used to create accurate timing for the turn-on delay with external

resistor and capacitor.

A decoupling capacitor (10 nF to 100 nF) on the VREF pin is required to ensure good noise

rejection.

5.3

Active Miller clamp

The TD352 offers an alternative solution to the problem of Miller current in IGBT switching

applications. Instead of driving the IGBT gate to a negative voltage to increase the safety

margin, the TD352 uses a dedicated CLAMP pin to control the Miller current. When the

IGBT is off, a low impedance path is established between the IGBT gate and emitter to carry

the Miller current, and the voltage spike on the IGBT gate is greatly reduced.

During turn-off, the gate voltage is monitored and the clamp output is activated when the

gate voltage goes below 2 V (relative to VL). The clamp voltage is VL+4V max for a Miller

current up to 500 mA. The clamp is disabled when the IN input is triggered again.

The CLAMP function does not affect the turn-off characteristic, but only keeps the gate at

low level throughout the off time. The main benefit is that negative voltage can be avoided in

many cases, allowing a bootstrap technique for the high side driver supply.

5.4

Turn-on delay

Turn-on (Ta) delay is programmable through external resistor Rd and capacitor Cd for

accurate timing. Ta is approximately given by (see Figure 5):

Ta (µs) = 0.7 * Rd (kΩ) * Cd (nF)

The turn-on delay can be disabled by connecting the CD pin to VREF with a 4.7 kΩ resistor.

Input signals with ON-time smaller than Ta are ignored.

8/18

Doc ID 11095 Rev 2

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