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Hot!MCP1703 catastrophic failure under light load

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RobotmanDDD
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2020/12/02 16:29:21 (permalink)
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MCP1703 catastrophic failure under light load

Using voltage regulator MCP1703T-5002E/CB

Input voltage:  12V
Output:  5V
Filter cap on output:  1u ceramic X5R 0603

The only load for this regulator is an analog VCO IC  SSI2130:
http://www.soundsemicondu...s/ssi2130datasheet.pdf

It draws about ~3mA and there is no crazy inrush currents on power up.

Problem:  after about 30 seconds  the MCP1703 fails by shorting the input to the output and thus delivering +12V to the SSI2130 (which is only tolerant to 5.25V) and then fries it. MCP1703 is then also permanently dead.

If instead use a 78L05 regulator there is no issue and the VCO IC is stable and works without fail.

What would cause such a catastrophic failure of the MCP1703?  Why would it not just shutdown instead of shorting input to output?
Is the output cap so critical in value that if too small it is making the MCP1703 unstable and causes it to short out ?

The parts used were purchased from Digikey and I would hope/trust they are genuine Microchip parts.
We have used this same part in many past designs (not with this VCO chip) and they have worked ok.

Is this possibly a bad batch? or is it a known issue with this line of regulators from Microchip?


#1

6 Replies Related Threads

    ric
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    Re: MCP1703 catastrophic failure under light load 2020/12/02 17:02:19 (permalink)
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    What is the source of the input 12V?
    Is there any chance it could spike over 16V?
     

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    #2
    RobotmanDDD
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    Re: MCP1703 catastrophic failure under light load 2020/12/02 17:10:33 (permalink)
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    The +12V source is from a well filtered and steady switching regulator
    LT3506EFE#PBF   it is within +/- 0.1% of +12V and has a ripple of about 10mV.
     
    No chance there would be a spike from this supply.
    #3
    PStechPaul
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    Re: MCP1703 catastrophic failure under light load 2020/12/02 17:37:39 (permalink)
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    Is there a bypass/filter capacitor close to the input of the regulator?

     
    #4
    RobotmanDDD
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    Re: MCP1703 catastrophic failure under light load 2020/12/02 19:29:53 (permalink)
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    Yes there is a 1U on the input as well.
    #5
    al_bin
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    Re: MCP1703 catastrophic failure under light load 2020/12/02 23:07:17 (permalink)
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    MCP1703  has a different pinout than 78L05
     
    Albert
    #6
    RobotmanDDD
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    Re: MCP1703 catastrophic failure under light load 2020/12/03 00:17:33 (permalink)
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    @albert
    yes i know this. I had to mod the circuit to accommodate the different pinout
    #7
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