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Positive and negative voltage transient on "Output" side of circuit.

Category: Hardware
Product Number: LTC4364

Dear forum members.

With reference to the circuit on page 23 figure 15.

We have a use case where the output of the above circuit is used to power external to the device, loads.
As such it will be exposed to transients and surges from this external environment.
We will be implementing transient protection in the form of Bi-Directional TVS diodes on the output but for various

reasons the worst case transient voltage that the output of the aforementioned circuit will be exposed to could be a high as

100 to 150V in both polarity's relative to GND (Return).
Notes: M1, M2, M3 and also CLoad have being upgrades to 250V devices.
Resistors were also updated to accommodate appropriate voltage / power related de-rating.

Questions"
1) What could be done to improve the survivability of the circuit when exposed to these transients.

2) Could M2 go into avalanche during these surge conditions?

Thank you

Regards 

  • Hi,

     

    Upgrading M1/M2/M3 to 250 V helps, but the critical requirement is ensuring the LTC4364 pins never see voltages beyond their absolute maximum ratings. M2 avalanche is possible if the transient or resulting overshoot exceeds its VDS capability. 
    If the residual output transient truly remains as high as ±150 V, an additional high-voltage bidirectional protection/disconnect stage should be placed between the external device and the LTC4364 circuit.
  • Hi tonie,
    Thank you very much for the feedback, I agree that the primary issue is with protecting the LTC4364's pins,
    Do you have any suggestions for implementing a high-voltage bidirectional protection/disconnect stage?
    The maximum current that the circuit has to supply will be no more than 500mA under normal conditions.

    Regards
    Olm

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