Author Topic: SMD PTC Fuse for 24 VDC  (Read 544 times)

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Offline AlinikTopic starter

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SMD PTC Fuse for 24 VDC
« on: July 18, 2023, 11:36:28 am »
Hello,
I am designing a new version of a PCB board with a microcontroller to drive two 24 V DC brushed motors, and I am looking for a self-resetting PTC SMD fuse for a 24 VDC supply line and max 2.5 A. The current spikes present upon activation of the motors can be up to 3 A for a maximum duration of 80 ms (this current refers to that read on the power supply when a motion command is sent to the motors). I am currently using component 0154003.DR (https://mou.sr/43iZNvz) but would like to replace it with a self-resetting fuse. I have identified component 2920L150DR (https://mou.sr/3O5OHp7) (Vmax 33 V, Ih 1.5 A, It 3 A) but would like to be sure it will fit.

In general for the fuses I know that:

the hold current (Ih) is the maximum current you can pass through, and guarantee the device will not trip over the specified temperature range;
the trip current (It) is the value where a maximum time-to-trip is characterised. Any current over this value is guaranteed to trip the fuse, within the specified temperature range.
Any current in between may or may not trip the device depending on environmental temperature, current, component variation and how long its had the current passing through.

The current drawn by the motors is then limited internally through the firmware on the microcontroller that stabilizes it below 1 A, so I think component 2920L150DR may be okay.
 

Offline temperance

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Re: SMD PTC Fuse for 24 VDC
« Reply #1 on: July 20, 2023, 03:00:36 pm »
Fuses are all about heat.

Check if the fuse can hold the required current over the intended temperature range because the trip time and the hold current go down with increasing temperature or way up at lower temperatures. Does the PCB itself heat up,...

Something to read for you to make proper decisions:
https://m.littelfuse.com/~/media/electronics_technical/application_notes/resettable_ptcs/littelfuse_polyfuse_ptc_selection_guide_application_note.pdf
 


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