IX4351NETR datasheet(8/10 Pages) IXYS

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INTEGRATED CIRCUITS DIVISION

www.ixysic.com

R01

IX4351NE

2.4 Negative VSS Charge Pump Regulator

The IX4351NE has an inverting charge pump

regulator that produces a negative regulated VSS

output. The charge pump operates in a closed-loop

mode creating VSS from VDD. The charge pump output

regulation is achieved by sensing the VSS voltage

through resistor divider R1 and R2. The charge pump

requires an external flying capacitor (CFLY), two

discrete Schottky diodes, a storage capacitor (CSS),

and a peak current limiting resistor (RFLY). VSS is set

by the R1 and R2 resistor divider:

2.5 Desaturation Detection and Protection

The desaturation protection circuit ensures the

protection of the external SiC MOSFET or IGBT in the

event of an over-current situation. The DESAT pin

monitors the drain voltage of the power SiC MOSFET

or the collector of the power IGBT via RDESAT and D1.

If the drain or collector voltage exceed the DESAT

Threshold Voltage (VTH,DESAT typically 6.8V) a

controlled turn-off sequence is initiated. OUTSRC is

turned off and OUTSOFT is turned on. The 900mA

sink capability of OUTSOFT allows an initial slow

turn-off of the external SiC MOSFET or IGBT. When

the GATE voltage decreases to the Soft Shutdown

Threshold Voltage (VTH,INSOFT typically 2.6V)

OUTSNK turns on and quickly pulls the GATE to VSS.

This two-step turn-off avoids dangerous dV/dt

over-voltages across the external SiC MOSFET or

IGBT.

The DESAT comparator is disabled for a fixed blanking

time (tBLANK) to avoid detecting a false desaturation

event during the external SiC MOSFET or IGBT

turn-on. The nominal tBLANK is 250ns, which can be

increased by adjusting RDESAT and CBLANK. This

blanking time starts when IN transitions from low to

high.

2.6 Thermal Shutdown

Thermal protection circuity turns off OUTSRC and

turns on OUTSNK and OUTSOFT when the junction

temperature reaches +160°C. OUTSRC is re-enabled

when the junction temperature cools to +140°C.

2.7 FAULT Output

The FAULT output signals if the IX4351NE is

undergoing a fault condition. The open-drain NMOS is

pulled low when VDD < VDDUV+, TJ=TSD, or a

desaturation is detected. FAULT is turned off when the

fault condition is remedied.

Figure 2. Timing Diagram

–

REG

-------







OUTSRC

OUTSNK

OUTSOFT

DESAT

FAULT

GND

TH,INSOFT

TH,DESAT

Hi-Z

OFF

OUTSOFTDLY

Hi-Z

BLANK

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