bd6709fs ROHM Co. Ltd., bd6709fs Datasheet - Page 36

• Manufacturer Part Number: bd6709fs
• Description: Dc Brushless Motor Drivers For Cooling Fans Speed Controllable Single-phase Full-wave Dc Brushless Fan Motor Drivers
• Manufacturer: ROHM Co. Ltd.

●Safety measure
1) Reverse connection protection diode
2) Measure against Vcc voltage rise by back electromotive force
Internal circuit impedance high
Reverse connection of power results in IC destruction as shown in Fig.46. When reverse connection is possible, reverse
connection protection diode must be added between power supply and Vcc.
Back electromotive force (Back EMF) generates regenerative current to power supply. However, when reverse
connection protection diode is connected, Vcc voltage rises because the diode prevents current flow to power supply.
When the absolute maximum rated voltage may be exceeded due to voltage rise by back electromotive force, place
(A) Capacitor or (B) Zenner diode between Vcc and GND. If necessary, add both (C).
GND
Vcc
In normal energization
amperage small
Circuit
block
(C) Capacitor and zenner diode
ON
Fig.97 Flow of current when power is connected reversely
ON
Each
pin
ON
(A) Capacitor
Fig.98 Vcc voltage rise by back electromotive force
Fig.99 Measure against Vcc voltage rise
Reverse power connection
GND
Vcc
ON
Large current flows
Thermal destruction
ON
ON
switching
Circuit
Phase
block
36/40
ON
Each
pin
(B) Zenner diode
ON
GND
After reverse connection
Vcc
destruction prevention
ON
No destruction
Circuit
block
ON
Each
pin