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AFE3010: AFE3010 operation issue with DPDT relay.

Haresh Patel
Prodigy 30 points
Part Number: AFE3010

Hello,

I am using DPDT relay instead of solenoid with AFE3010.

In my circuit the relay coil is control through the SCR. The coil resistance is 32K.

While testing this circuit, SCR turned on. When I change relay with another relay having 16K coil resistance, it is working properly.

While going in detail I found the issue is due to SCR_TST pin. Which is checking the SCR integrity test.

Please suggest how to resolve this issue. I think tuning of R11 is required. But, how to tune.

  • 0
    TI__Mastermind 28515 points

    Hello valued engineer,

    Does the erroneous SCR fire happen immediately after power up or 5 seconds after power up?

    You can test if this is a SCR self-test issue by floating the SEL pin, which disable SCR self test.

    If the issue is still happening, then try shorting SCRTST and PH pins together with SEL=floating. If this works, then the issue is with the continuous, solenoid self-test of the SCRTST pin.

     If neither of these things make the erroneous SCR firing go away, then the root cause is somewhere else. Although it seems unlikely given that you fix the problem by reducing coil resistance.

    Unfortunately regardless of whether this is due to periodic SCR self-test or SCRTST's continuous test, tuning R11 is limited to something in between 45kΩ and 69kΩ for any line voltage. You could try this and/or placing a small 100pF cap a SCRTST pin.

    I believe this is due to the continuous self test and that the impedance between SCRTST and line during positive cycle is too great causing the pin to miss measuring zero crossings.

    Note that measuring this SCRTST pin voltage with oscilloscope probe is difficult because of sensitivity to leakage and may induce an error.

    Sincerely,

    Peter