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Original question:

LMG3410R070: LMG3410

LMG3410R070: LMG3410 Fault issue

user5959586
Prodigy 10 points
Part Number: LMG3410R070
Other Parts Discussed in Thread: LMG1210

I designed a sweep frequency power supply for the mass spectrometer, referring to the circuit of Figure 14 in LMG3410 datsheet. During debugging, a 6.3KHz Fault signals were found in the lower LMG3410 transistor.  There are three situations where faults can occur, over-temperature, over-load and under voltage. But none of these three cases was found.

I don't know why this fault signal appears？

Please ignore U21 and U23, they are NE.

HVHF PAGE3.pdf

  • 0
    TI__Intellectual 805 points

    Hello,

    I had a look at the schematics. From LMG3410R070 circuitry side, I don't see a problem. Only IN resistors are pretty large which can add a large delay. I have a few questions and comments here;

    • Are you using LMG1210 to generate PWM pulse from a single pulse?
    • What is the switching frequency?
    • For how long do you see the FAULT signal going low?
    • Yes there are only these 3 faults.  It is unlikely that OCP and OTP protections are kicking in because you OCP latches the device off and you need to keep PWM signal low for 300us to restart. Fault signal from OTP would not get in out so quickly because of thermal time constants. I incline towards a UVLO fault. But UVLO can be due to ground bouncing if layout is not following the rules mentioned in the datasheet. 
    • The RDRV is 15k. This is the highest dv/dt setting, which would give you 100V/ns transitions. This may cause large di/dt current and cause voltage spikes to bounce the ground if layout is not proper. I would recommend to change it with 140k to see if the problem still exists.

    Regards,

    Serkan