New Industry Products

Littelfuse Introduces 1 Amp, 60 Volt Solid State Relay

February 01, 2021 by Gary Elinoff

The fault-protected, normally open CPC1561B solid state relay (SSR) features built-in thermal shutdown and current limiting circuitry.

The CPC1561B is said to be the highest current, normally open SSR on the market today that also includes both of these important protections.


The CPC1561B.
The CPC1561B. Image courtesy of Mouser


The small, surface-mounted CPC1561B SSR is offered by IXYS, a Littelfuse company. With its dual fault protection, the SSR provides a robust solution for tough applications that wouldn’t be possible with either electro-mechanical relays or with conventional SSRs.

As per  Steve Andrezyk, Director of Marketing for Littelfuse-IXYS Integrated Circuits "The CPC1561B is ideal for markets and applications that cannot be down for long periods of time due to over current, over temperature and electrical stress" He goes on to state that, "The CPC1561B output relay can survive harsh conditions and resume normal operation once the fault is removed, thus reducing product downtime and potentially eliminating service call time as the SSR both protects itself and resets to resume normal operation."


Key Features of the CPC1561B Solid State Relay

The Current Limit Control Block, aka the Active Current control, regulates the MOSFET gate drive in the event of overcurrent conditions.

The Thermal Shutdown Block senses the SSRs temperature, and at a die temperature of 128℃, directs the Current Limit Control to block current,

Auto Reset directs the device to resume normal operations once a fault corrects itself. No operator intervention is required. This important feature reduces the downtime of the devices being protected.


Block diagram of the CPC1561B SSR.
Block diagram of the CPC1561B SSR. Image courtesy of Littelfuse's datasheet.


Littelfuse also offers a very helpful video describing the CPC1561B.

Unlike standard SSRs or mechanical relays, the CPC1561B enhances the survivability of electronic circuitry through active current limiting, In addition, the LED signaling methodology offers input-output galvanic isolation of 3750 VRMS.


Device Specifics

The  CPC1561B can switch AC or DC loads up to one amp at 60°C. After that temperature point, capacity decreases linearly to about 700 mA at 85℃.

Maximum On-Resistance is 245 mΩ

The maximum input current to the LED needed for device activation 2.5 mA, but at temperatures over 60℃, 5mA is recommended.

Turn On and Turn Off, subject to conditions described in the datasheet are typically

  • TON is 1.2 ms  
  • TOFF is 0.06 ms

Output Capacitance and Input to output capacitances are 170pF and 1pF, respectively


Other IXYS/Littelfuse SSRs

The company offers an array of single-pole, normally open SSRs with similar features. They are listed in a separate product page. These devices also serve to replace electromechanical relays but do not offer the current carrying capacity of the CPC1561B.



  • Smart homes 
  • Gaming
  • Building Automation
  • IoT 
  • Battery-powered systems 
  • Instrumentation 


Physical Considerations

  • The new SSR is available in a 16-pin SOIC package. Measurements, including the gull wings, are 10.312 by 10.21 by 2.338 mm.
  • The unit operates over a temperature range of -40 to +85°C 


Environmental and Regulatory Information

  • Flammability rating as per UL 94 V-0 
  • UL 1577 Recognized Component: File Pending 
  • ESD susceptibility, as per the human body model, is 3kV
  • Moisture sensitivity, as per IPC/JEDEC J-STD-033, is MSL 3