Obsolete

Product(s)

- Obsolete

Product(s)

AN1645 - APPLICATION NOTE

6/22

device can still working properly; otherwise a diode D1 connected to Vcc or a zener diode must be added

to protect the device.

Figure 7: Synchronization with a diode and pull-up resistor

Figure 7 shows the synchronization circuit with diode and pull-up resistor. In this case there is no

problem with the turn-off spike and maximum CK pin voltage. This circuit cannot work properly in

Discontinuous Mode due to the ringing present in the voltage drain of the synchronous rectifier.

Figure 8: Shut-down circuit

The STSR2P can be easily turned off adding a NPN transistor between Ck and SGLGND. This transistor

forces the CK pin to GND when the signal OFF is high. In this condition OUTGate1 and OUTGate2 will

be in a low state turning off the Synchronous Mosfets.

+5V

+5V

FREE WHEEL

R1

D1

STSR2P

4

5

2

6

3

Ck

INHIBIT

Vcc

SGLGND

SETANT

FORWARD

+5V

+5V

OFF

R1

D1

NPN

Q1

R2

FREE WHEEL

FORWARD

STSR2P

4

5

2

6

3

Ck

INHIBIT

Vcc

SGLGND

SETANT