L497 datasheet(8/11 Pages) STMICROELECTRONICS

8 / 11 page

OTHER APPLICATION NOTES

DUMP PROTECTION

Load dump protection must be implemented by an

external zener if this function is necessary. In fig. 4

DZ2 protects the driver stage, the connection be-

tween pin 6 and 7 protects the output transistor of

pin 6. MoreoverDZ1 protectsboth the power supply

input (pin 3) and Hall-effect sensor.

Resistor R4 is necessary to limit DZ1 current during

load dump.

OVERVOLTAGE LIMITATION

The external darlington collector voltage is sensed

by the voltage divider R2,R3. The voltage limitation

increases rising R2 or decreasing R3.

Due to the active circuit used, an Ro Co series net-

work is mandatory for stability during the high vol-

tage condition.

Ro Co values depend on the darlington used in the

application.

Moreover the resistor R13 is suggested to limit the

overvoltage even when supply voltage is discon-

nected during the high voltage condition.

REVERSE BATTERY PROTECTION

Due to the presence of external impedanceat pin 6,

3, 16, 15 L497 is protected against reverse battery

voltage.

NEGATIVE SPIKE PROTECTION

If correct operation is requested also during short

negativespikes,the diode DS and capacitorCs must

be used.

Figure 4 : Application Circuit.

L497

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