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LMR16010: FMEA of part

Joe Gleason
Prodigy 100 points
Part Number: LMR16010

Hello expert,

I am doing an FMEA of the 5V regulator and wondering what the expected VOUT and effects are for the following cases. See simplified schematic and component values listed below.

  1. Short CBoot 
  2. Open CBoot
  3. Short L
  4. Short Rfbt  
  5. Open Rfbt
  6. Short Rfbb 
  7. Open Rfbb
  8. Short Rt
  9. Open Rt
  10. Open D
  11. Open Cout
  12. Short Cout

Component values used for 5V output:

  • Cin = 10uF
  • Rt = 32.4kohm
  • Cboot = 0.1uF
  • L = 10uH
  • Rfbt = 100kohm
  • Rfbb = 17.6kohm
  • Cout = 22uF

Thanks,

Joe

  • 0
    TI__Genius 10685 points

    Hi Joe, 

    I will review and get back to you tomorrow. 

    Regards,

    Harrison 

  • +1 in reply to Harrison Overturf
    TI__Genius 10685 points

    Hi Joe,

    I've copied your conditions and outlined the expected VOUT state below:

    1. Short CBoot - Loss of output, device not damaged
    2. Open CBoot - loss of output, device not damaged
    3. Short L - No output, possible device damage
    4. Short Rfbt - Vout regulates to 0.75V (VREF)
    5. Open Rfbt - Output follows VIN
    6. Short Rfbb - Output follows VIN
    7. Open Rfbb - VOUT regulates to ~0.75V
    8. Short Rt - Switching frequency is not defined, Vout undefined.  
    9. Open Rt - Switching frequency is not defined, Vout undefined. 
    10. Open D - Device unable to regulate output
    11. Open Cout - Device unable to regulate output
    12. Short Cout - output voltage approaches 0V, device operates in current limit

    Regards,

    Harrison 

  • 0 in reply to Harrison Overturf
    Prodigy 100 points

    Thank you for the feedback Harrison. I have some additional FMEA cases I hope you can help answer:

    1. Pin 4 (RT) shorts to power, which will exceed max rating of RT pin. Fail safe?
    2. Pin 5 (FB) is floating. What is output voltage?
    3. Pin 5 (FB) shorts to power (12-21V). 
    4. Pin 5 (FB) shorts to pin 6 (PGOOD). What is the effects and output voltage?
    5. Pin 8 (SW) short to power (12-21V).

    Thanks,

    Joe

  • +1 in reply to Joe Gleason
    TI__Genius 10685 points

    Hi Joe, 

    Please find my answers below:

    1. Pin 4 (RT) shorts to power, which will exceed max rating of RT pin. Fail safe? - The RT pin (or any pin for that matter) should not exceed the ratings in the Absolute Maximum Ratings Table. Stresses beyond those listed in this table may cause permanent damage to the device. 
    2. Pin 5 (FB) is floating. What is output voltage? - VOUT will approach the input voltage. 
    3. Pin 5 (FB) shorts to power (12-21V). - Same as #1. 
    4. Pin 5 (FB) shorts to pin 6 (PGOOD). What is the effects and output voltage? - If PGOOD is pulled to GND then this will cause the output to follow VIN if PGOOD is floating then this is the same as #2 above, and if PGOOD is pulled up to an appropriate logic level (3.3V for instance) the output voltage will decrease towards 0V. 
    5. Pin 8 (SW) short to power (12-21V). - Damage to the device my occur. 

    Regards,

    Harrison Overturf