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AFE3010: Open Solenoid and Open Diode Bridge self testing - more info needed

David Salgueiro
Prodigy 110 points
Part Number: AFE3010

Hello,

In the datasheet for the AFE3010, Section 7.3.7.2 reads:

1. Open Solenoid Test: The AFE3010 checks for transition of AC line signal at the PH and SCR_TST pins. If the device does not detect a transition of the line signal at PH or SCR_TST pins for approximately 100 ms, then the device reads a self-test fail.

2. Diode Bridge Test: if a diode is shorted in the diode bridge rectifier, the device is able to detect the variation in supply current from the diode bridge. This detection is considered a self-test fail, and the AFE3010 fires the SCR and sets the ALARM blinking at 1-s intervals (for 60-Hz systems).

Question A) If the SCR Test feature is disabled on the AFE3010, does the AFE3010 still self-test for the solenoid coil = open failure?

Question B) For datasheet item 1, what is the transition (voltage threshold and duration?) that is required to pass the solenoid open coil self-test?

Question C) For datasheet item 2, How exactly does this work? 

  • +1
    TI__Mastermind 31125 points

    Hey David,

    A) Yes. Disabling the SCR test feature (SEL=floating) only disable the device's ability to detect failures with the SCR. If the solenoid coil=open, the device will still see this via the lack of AC transitions at SCR_TST pin.

    B) The criteria for the solenoid open fail is that it does not register any zero-crossings for about 12 cycles, so 100ms on a 60Hz line. The criteria for a zero-crossing is based upon a comparator reading the pin. The PH and SCRTST pins are clamped to the internal 20-V rail and are monitored with comparators. The threshold for these comparators are low level and the input voltages are divided down with current limiting resistances. After being powered on for a full cycle, the device calculates the period of line voltage and then expects to see a zero-crossing according to this time within +/- a little less than a half cycle.

    C) The device monitors this by looking for large changes in the VDD current that follow the phase voltage and occur when one of the diodes in the rectifier become shorted. If these large current swings occur for ~100ms, then this will trigger the diode bridge failure mode.