Circuit Protection I Current Regulating Diodes I ATC Semitec

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Semitec’s range of CRD Current Regulating Diodes (sometimes called current limiting diodes or constant current diodes) offers a very simple way of providing constant current over a wide voltage range. They offer protection, stability and control when driving LEDs, optocouplers & battery-charging circuits.

Over a wide voltage range from 1V to 100V, Semitec CRDs can stabilise a current at a fixed value. By using a single constant current diode in your circuit, voltage changes, load resistance changes or ripple voltage effects will not affect the through current value. Recreating a constant current circuit such as this would require several components whereas using a Semitec CRD you only need one simple part to achieve the same result.

This offers the advantage of simplifying product assembly and minimises the component count, particularly useful in space critical applications where board space is a premium. SMD stock parts include the following;

S-101T, S-301T, S-501T, S-701T, S-102T, S-152T, S-202T, S-272T, S-352T, S-452T, S-562T, S-822T, S-103T, S-123T, S-153T, S-183T, S-223T

Applications

LED brightness stabilisation
LED street lights, light bulbs and downlighters
Constant voltage/current circuits for Zener diodes
Constant current source for proximity and other sensors
Battery charging/discharge circuits
DC-DC converters

For further technical information, see our Frequently Asked Questions section

Call us today on 01606 871680 or complete the Contact us form, to discuss your application’s thermal sensor requirements. Using our extensive technical knowledge and innovative supplier base, we will work with you to provide the optimum solution for your product.

CRD Constant Current Diodes
CRDs are current regulating diodes (or constant current diodes) that help to maintain a fixed current value over a wide voltage range.
Constant current values from 0.1mA to 22mA
Operating temperature range: -40°C to 150°C
Can be used in parallel or in series with Zener diodes
View Product Details
Semitec CRD Constant Current Diode.pdf

How do Current Regulating Diodes (CRDs) work?
CRDs (current regulating diodes) are diodes that maintain a constant current flow despite fluctuations in the voltage, over a wide range of voltage, from less than 1V to 100V.
Creating a constant current circuit generally involves multiple components. At ATC Semitec, we supply CRDs by Semitec, which provide the same function but as a single component.
This provides a concise, cost effective solution where space is limited.
Have a question or need a sample ? Call one of our engineers today on 01606 871680
When would you use Circuit Protectors?
Circuit protectors offer circuit protection in devices in a manner that is far superior to using fuses.
This makes them ideal for applications containing:
Relay circuits
Motors
Heaters
Transformers
Solenoids
Semiconductors
Our CRD‘s from Semitec have a wide range of operating voltages that they can steady current over, and their small size makes them a neat solution in tight spaces.
What are PTC Resettable Fuses?
PTC or Polymer PTC (PPTC) fuses carry current up to a threshold temperature. At this point, the crystalline polymer structure will change to an amorphous state, leading to a massive increase in resistance, preventing charge from being carried across the device.
The device will then remain in this high resistance state until the applied voltage is removed and they have cooled down, allowing the polymer structure inside to return to its original crystalline form. Hence, they are considered re-settable.
At ATC Semitec, we have a range of different PTC resettable fuses for use over many currents and operating temperatures.
To have a look at our current range of devices, click here.
Have a question or need a sample ? Call one of our engineers today on 01606 871680
What are the different types of Circuit Protection?
There are many different types of circuit protection devices due to the multiple different ways that current can be limited in a circuit. At ATC Semitec, we have a range of different circuit protects to suit your appliance.
From our repeat use Inrush Current Limiters from Thinking TKS, designed to protect front-end mains voltage supplies against current spikes at switch-on, to our SEFUSE Thermal Fuses from SCHOTT which offer one-shot ultimate thermal protection from 70°C to 240°C, our range can tailor to your requirements.
For more information, and to see our full range of devices, click here.
Have a question or need a sample ? Call one of our engineers today on 01606 871680
What are Circuit Protectors?
Circuit protection devices protect the circuit from excessive temperatures, currents or short circuit in an electrical conductor. They are essentially ‘weak links’ within the circuit that are designed to fail when a fault in the system is encountered. By breaking at low currents, they limit the amount of energy that is released during electrical failure, leading to safer devices.
From PTC resettable fuses, to CRDs, to MOV’s, we have an array of different devices to that can be implemented.
To see our full range of Circuit Protection Devices, click here.
Have a question or need a sample ? Call one of our engineers today on 01606 871680

Industrial Applications

CRDs - Constant Current Diodes