NFAQ1560R43TL

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11

FAULT Pin

The FAULT output is an open drain output requiring

a pull−up resistor. If the pull−up voltage is 5 V, use a pull−up

resistor with a value of 6.8 k

W or higher. If the pull−up

voltage is 15 V, use a pull−up resistor with a value of 20 k

W

or higher. The FAULT output is triggered if there is a VDD

undervoltage or an overcurrent condition.

Under−voltage Protection

If VDD goes below the VDD supply under−voltage

lockout falling threshold, the FAULT output is switched on.

The FAULT output stays on until VDD rises above the VDD

supply under−voltage lockout rising threshold. After VDD

has risen above the threshold to enable normal operation, the

driver waits to receive an input signal on the LIN input

before enabling the driver for the HIN signal.

Overcurrent Protection

An over−current condition is detected if the voltage on the

ITRIP pin is larger than the reference voltage. There is a

blanking time of typically 350 ns to improve noise

immunity. After a shutdown propagation delay of typically

1.1

ms, the FAULT output is switched on. The FAULT output

is held on for a time determined by the resistor and capacitor

connected to the CFOD pin. If RCLR = 2 M

W and CCLR =

1 nF, the FAULT output is switched on for 1.65 ms (typ.)

because the FAULT pin goes back to high impedance when

CFOD is higher than 8 V (typ.).

The over−current protection threshold should be set to be

equal or lower to 2 times the module rated current (Io).

An additional fuse is recommended to protect against

system level or abnormal over−current fault conditions.

Capacitors on High Voltage and VDD Supplies

Both the high voltage and VDD supplies require an

electrolytic capacitor and an additional high frequency

capacitor. The recommended value of the high frequency

capacitor is between 100 nF and 10

mF.

SD Pin

The SD terminal pin is used to enable or shut down the

built−in driver. If the voltage on the SD pin rises above the

VSD+ voltage, the output drivers are enabled. If the voltage

on the SD pin falls below the VSD− voltage, the drivers are

disabled.

Minimum Input Pulse Width

When input pulse width is less than 1

ms, an output may

not react to the pulse. (Both ON signal and OFF signal)

Calculation of Bootstrap Capacitor Value

The bootstrap capacitor value CB is calculated using the

following approach. The following parameters influence the

choice of bootstrap capacitor:

15 V is recommended.

8 nC.

Specified as 12 V.

Specified as 0.4 mA.

IGBT.

Capacitance calculation formula:

CB = (QG + IDMAX * TONMAX)/(VBS − UVLO)

CB is recommended to be approximately 3 times the value

calculated above. The recommended value of CB is in the

range of 1 to 47

mF, however, the value needs to be verified

prior to production. When not using the bootstrap circuit,

each high side driver power supply requires an external

independent power supply.

The internal bootstrap circuit uses a MOSFET. The turn

on time of this MOSFET is synchronized with the turn on of

the low side IGBT. The bootstrap capacitor is charged by

turning on the low side IGBT.

If the low side IGBT is held on for a long period of time

(more than one second for example), the bootstrap voltage

on the high side MOSFET will slowly discharge.

Figure 15. Bootstrap Capacitance versus Tonmax

0.01

0.1

1

10

100

0.1

1

10

100

1000

Tonmax (ms)