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LMD18200: OCP Delay During Initial Power-Up with Shorted Output

ArTzy
Mastermind 20350 points

Part Number: LMD18200

Hi Experts,

We'd like to ask assistance/clarification about  LMD18200:

We accidentally powered up the device with a shorted output load. The supply voltage ramped up in 10µs. We noticed that the very first overcurrent protection (OCP) trigger took about 4–5ms to activate. After this initial event, the IC entered its standard repetitive cycle, turning on and shutting down every 8µs.

Does the LMD18200 experience an inherent delay or a slower top-side MOSFET gate-drive turn-on time specifically during the initial power-on state?

Thank you.

Regards,
Archie A.

  • 0
    TI__Genius 17511 points

    Hello Archie,

    Thanks for your question.

    The LMD18200 uses an internal charge pump driven by a 300 kHz oscillator to generate the gate-drive voltage for the high-side (sourcing) DMOS switches. The gate must be driven approximately 8V above the supply voltage, and the charge pump achieves this by alternately switching an internal capacitor to ground (charging it to ~14V) and then connecting it above V_supply. The rise time of this drive voltage is typically 20 μs which is suitable for operating frequencies up to 1 kHz.

    Thanks,

    Ibinu