Post Go back to editing

LTC7000IMSE's VCC failed

Category: Hardware
Product Number: LTC7000IMSE

The design has 200K-ohm resistor connected from VCC to INP. A bootstrap diode with 1uF capacitor is connected to VCC. When 26V was applied to VIN and RUN pin is above turn-on threshold.  Of 10 similar circuits,  3 LTC7000IMSE failed to output 10.3V on VCC. The gate drive resistor is 7.5K from TGUP pin. We replaced 3 failed LTC7000 but still have one failed. The test is with 100K-ohm load

Question: Would the design overstressed and damaged internal VCC regulator? 

Parents
  • Two MOSFETs back-to-back connected with gate charge = 232nC and gate resistor =1K ohms are used in simulation with output load  = 1 ohm. The charge current to bootstrapped capacitor is increased to 17.6mA to19mA and a peak current of 85mA observed when the gate plateau voltage just reached. 

    So, the startup current  from internal regulator will increase with the output load, MOSFET total gate charge, the bootstrapped capacitance, and MOSFERT external gate resistance. So, what is the power limitation of the internal regulator during startup period?

  • If LTC7000 internal regulator were not adequate to provide power,  could we add LT3012 to charge bootstrapped capacitors. Question: If  LTC7000's VIN is also connected to LT3012's IN, could we turn on LT3012 before LTC7000 enabled? LTC7000's BST-TS will have LT3012's OUT voltage across it before enabled.

Reply
  • If LTC7000 internal regulator were not adequate to provide power,  could we add LT3012 to charge bootstrapped capacitors. Question: If  LTC7000's VIN is also connected to LT3012's IN, could we turn on LT3012 before LTC7000 enabled? LTC7000's BST-TS will have LT3012's OUT voltage across it before enabled.

Children
No Data