CPC1560 Datasheet, PDF (12/14 Pages) Clare, Inc. – Solid State Relay with Integrated Current Limit

CPC1560
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
inductive load (L_LOAD).
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
be considered¹. Of paramount importance is that the
designer know the characteristics of the load being
switched.
Figure 2. CPC1560 DC-Only Configuration with Over-Voltage Protection
CPC1560
C+
C_EXT
R
18
LED
V
IN
2 7 ^Output
Z
LOAD
Supply
3 6 _Output
45
C-
D
OVP
Supply
Figure 3. CPC1560 AC/DC Configuration with Over-Voltage Protection
CPC1560
C+
C_EXT
R_LED
18
V
IN
Output
27
3 6 ^Output
C-
45
Z_LOAD
D
OVP
Supply
1 _{For more over voltage protection techniques consult:}
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
12
PRELIMINARY
R00F