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PMP7282: PWM IC failure due to Master Slave configuration

Nesh Johny
Expert 1310 points
Part Number: PMP7282
Other Parts Discussed in Thread: LM5116

Dear Sir,

1.What are the situations where the master PWM IC (LM5116) can get damage due to master slave configuration?

2.If we use separate auxiliary 5V supply (common ground) for Sync generation and feedback opamp (LMC7101AIM5). which also starts 5 seconds before the master and slave PWM controllers get power. Is there any chance of instability or failure.

3. what are the major things to be considered while using LM5116 in master slave configuration?

thanks and regards,

Nesh

  • 0
    TI__Intellectual 1235 points

    Hi Nesh,

    1. None. The only direct pin connections between the master and slave ICs are VIN, VOUT and PGND, AGND. The SYNC and COMP pins are not direct connections.

    2. A separate 5V supply for sync and feedback is fine. There should be no issue.

    3.  The external feedback amplifier reference voltage must match the internal FB reference of 1.2V. A scale factor of 10K/4.99k and 4.99k/10k is used  to meet the dynamic range of the COMP voltage. Keep the sync signal away from the power stage switching. A 27pF capacitor for C44 is used to keep switching noise out of the sync.

    In general make sure that the VIN and SW pin voltages are below the maximum ratings. Input filter damping is critical, so use the recommended values on the schematic note 4.

    Best Regards,

    Bob Sheehan

  • 0 in reply to Bob Sheehan
    Expert 1310 points

    thank you sir for the reply