CPC1560

12

PRELIMINARY

R00F

5.7.2 Protection Methods

One way to protect the CPC1560 and application

circuit components from damage when excessive

stored energy is suddenly released into the output

MOSFETs of the CPC1560, is to add a Transient

Voltage Suppressor (TVS) across the output switches.

Use a unidirectional TVS from the outputs to C- for the

DC-only configuration, and use a bidirectional TVS

across the output pins for the AC/DC configuration as

shown in the diagrams below.

In order to calculate the required TVS value, the user

has to compare working voltage of the application

circuit to the breakdown voltage of the CPC1560 with

the TVS maximum clamping voltage ratings. The TVS

maximum clamping voltage capability must be, at a

minimum, equal to the specific peak pulse current of

the load. This must be done to ensure the TVS can

easily absorb any excess energy coming from the

In addition to the TVS, other protection techniques are

also available depending on the type of load the user

is trying to switch. For purely resistive loads the user

may rely on the output transistor to handle any

parasitic energy. For very low to moderately inductive

loads (e.g. remote switching of a load through a long

cable), a voltage suppressor or TVS can be used as

explained before. For heavily inductive loads, a

fly-back diode connected across the load element is

recommended

For much higher inductive loads, other circuit

techniques, device ratings and/or protector types must

designer know the characteristics of the load being

switched.

Figure 2. CPC1560 DC-Only Configuration with Over-Voltage Protection

Figure 3. CPC1560 AC/DC Configuration with Over-Voltage Protection

Switchmode Power Supply Handbook, 2nd Edition,

Keith Billings, ISBN 0-07-006719-8, or Power

MOSFET Design, B.E. Taylor, ISBN 0-471-93-802-5

Supply

Supply

D

OVP

C

EXT

CPC1560

R

LED

V

IN

1

2

3

4

8

7

6

5

Z

LOAD

C+

C-

Output

Output

Supply

D

OVP

C

EXT

CPC1560

R

LED

V

IN

1

2

3

4

8

7

6

5

Supply

Z

LOAD

C+

C-

Output

Output