SiC641, SiC641A

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Vishay Siliconix

S19-0864-Rev. A, 21-Oct-2019

7

Document Number: 77191

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TMON/FAULT Temperature Monitor and Fault Flag

Functions

The TMON/FAULT output is used to report operating

conditions detected by the logic of the driver that require

attention.



A fault is reported by the TMON/FAULT output going high to

3.3 V.



The reported conditions are high temperature, insufficient

bootstrap

voltage,

persistent

over-current,

high

side

MOSFET short.



The TMON/FAULT output also reports the operating

temperature of the SiC641.



The temperature is converted to a voltage with a conversion

gain of 8 mV/°C and a target value of 600 mV at 0 °C.

In a multi-phase topology, all TMON/FAULT signals are

connected to the PWM controller and will indicate the temp.

of the warmest device.



If

the

operating

temperature

exceeds

140

°C

the

TMON/FAULT output will signal a fault condition. The fault is

reset when the temperature is below the temperature

hysteresis threshold.



For proper operation, the TMON output must be biased with

a resistor to ground. A 1 k

 resistor is recommended.The

SiC641 also has an over temperature shutdown feature that

stops operation when the temperature is above 160 °C.



The over temperature shutdown fault is reset by DISBL#

cycling or power cycling.

Over Current Protection Function

The SiC641 is equipped with over-current protection.



An over-current condition will also be reported through

the TMON/FAULT flag. The flag is automatically reset after

128 switching cycles that do not trigger the protection.



When the output current exceeds safe operating levels the

SiC641 will protect the power devices by forcing an early

termination of the high side conduction time and eventually

folding the operating frequency (skipping PWM cycles) as

needed.

High Side MOSFET Short Detection

A failure of the high side MOSFET may cause significant

system damage. For this reason the SiC641 monitors the

switching node (PHASE) cycle by cycle in order to promptly

detect a short of the high side power device.



After four consecutive HS short condition cycles are

detected, the SiC641 will report the fault with the

TMON/FAULT flag, and will ignore the incoming PWM signal.

The low side MOSFET is activated to protect the load from

high voltage.



The fault flag can only be reset by cycling power to the

driver’s logic.



FUNCTIONAL BLOCK DIAGRAM

Fig. 3 - Functional Block Diagram

0.8

1.72

3.0

115

25

140 160

Temp. (°C)

VTMON/FAULT (V)

T

module = (VTMON/FAULT - 0.6)/0.008

ZCD_EN#

V

SWH

GL

UVLO

UVLO

PWM logic

and protection

Driver and

anti-cross conduction control logic

Zero-cross detection

Over current protection

HS short detection

Temperature

monitor

BOOT

VIN

PWM

C

GND

PGND

PHASE

V

CC

V

IN_S

DSBL#

T

MON/FAULT

BOOT

V

CC

VREF = 1 V

VREF = 1 V