A resettable fuse, also known as a PTC (Positive Temperature Coefficient) fuse or a polymeric positive temperature coefficient (PPTC) device, is an electronic component used to protect circuits from excessive current. It differs from a traditional fuse in that it can automatically reset itself after the fault condition is removed, whereas a traditional fuse requires replacement once it is blown.
Resettable fuses are made of a polymeric material that exhibits a positive temperature coefficient of resistance. This means that as the current passing through the fuse increases, its resistance also increases. When the current exceeds a certain threshold, the fuse heats up, causing the resistance to rise significantly and limiting the current flow to a safe level.
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The selection of a resettable fuse for a design typically involves considering the following factors:
Current rating:
Determine the maximum current that the fuse needs to handle under normal operating conditions. This value should be chosen to protect the circuit without unnecessarily tripping the fuse during normal operation.
Hold current:
It refers to the maximum current that the resettable fuse can sustain without tripping. It is important to ensure that the hold current is higher than the normal operating current of the circuit.
Trip current:
This is the current at which the fuse will trip and limit the current flow. It should be set below the maximum allowable current for the protected circuit.
Time-to-trip:
Consider the response time of the resettable fuse to ensure it trips quickly enough to protect the circuit. This parameter is usually specified by the manufacturer and should be compatible with the circuit's requirements.
Voltage rating:
Choose a resettable fuse with a voltage rating that is suitable for the circuit's operating voltage.
Environmental considerations:
Consider factors such as operating temperature range, humidity, and any specific environmental conditions that may affect the performance of the resettable fuse.
Size and package:
Consider the physical size and package of the resettable fuse, ensuring it fits within the available space in your design and is compatible with the manufacturing and assembly processes.
Ambient temperature:
Take into account the operating environment temperature range to select a resettable fuse that can withstand those conditions without false tripping or performance degradation.
Packaging and physical dimensions:
Consider the available space and form factor constraints within the design to choose a resettable fuse that can be easily integrated.
Based on datasheets and guidelines provided by the resettable fuse manufacturers for detailed specifications and selection guidance specific to our application based criteria will be best practice on the fuse selection..