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CSD18543Q3A: Looking for a low cost SSR solution to replace a mechanical relay

Noam Weidenfeld1
Intellectual 780 points
Part Number: CSD18543Q3A

Hi,

Today I am using a mechanical relay as digital input to my board.

I want to replace it, cost and size, with an SSR. The application is Unidirectional.

I noticed the CSD18543Q3A as an option. Any other suggestion will be welcome.

Thanks

Noam

  • 0
    TI__Expert 6855 points

    What part you use all depends on the voltage required and the current needed. If you know the current you can simply use I*I*R equation to calculate power dissipation, with about 3W being a max number typical for a typical pcb but you thermal environment dictates if 3W is typical.

    On the web here.     There is a number of other resistance choices to select the best fet, higher resistance fets will generally be lower cost.

    Chris

  • 0 in reply to Chris Bull
    Intellectual 780 points

    Chris Hi,

    Do you have an application note showing how to use a single MOSFET as an SSR for DC switching?

    Noam

  • 0 in reply to Noam Weidenfeld1
    TI__Mastermind 18200 points

    Noah,

    I am not aware of such an app note, but since the FET is used more or less as a load switch, the critical things to look at would be can the FET handle the current (is the resistance low enough to keep conduction losses low)

    And if the FET has to handle certain current surges in the saturation region, when the FET is not fully enhanced (Vds and current are both high for a certain duration), then you must also make sure you stay within the confines of the safe operating area.