NJM2640

-7 -

There are two methodologies to consume kick back voltage:

1) By insertion of ZD1 (zenner diode connected between Base and Emitter of TR1)

Energy of kick back voltage is consumed by TR1(or TR2). When ZD1 is in operation, Collector

voltage is sum of Vbe and ZD1. Therefore, breakdown voltage of ZD1 must be lower than that of

TR1.

2) By insertion of ZD2 (zenner diode connected between Collector and Emitter of TR1)

Energy of kick back voltage is consumed by ZD2. To protect TR1, breakdown voltage of ZD2 must be

lower than that of TR1.

This method is generally used when Energy of kick back voltage is large. In such application, power

rating of ZD must take in consideration.

6. VCC input (Design of Ra and Ca)

Ra and Ca must be used if VCC exceeds operating voltage range of NJM2640.

Example) VCC 60V Application

Given that current consumption of NJM2640 is 4mA (at VCC=48V), Ra is given by:

Ca is used if NJM2640 is oscillated or shows unstable operation. A typical value Ca is from 0.01

µF to

0.1

µF. A ceramic type is recommended and it must be place near VCC and Gnd.

Inserting Ra and Ca also improves ESD immunity.

7. Protection from active power on and off (D2)

If an application requires active power on and off, TR1 (TR2) may be damaged or resulted in

destruction.

In such application, adding diode between motor winding and Gnd will reduce the damage.

Ω

=

×

−

=

−

k

Ra

3

10

4

48

60

3

The specifications on this data book are

only given for information, without any

guarantee as regards either mistakes or

omissions. The application circuit in this

data book are described only to show

representative usages of the product

and not intended for the guarantee or

permission of any right including the

industrial rights.