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LT8391A

Dear all,

There is a problem with the EVM (DC2575A) circuit.

What is the function of D5 (PMEG3010EB) in the circuit?

Is it necessary?

Thanks.

  • Hello samaon,

    D5 serves to protect some of the IC pins from going negative if there is a sudden short circuit at the end of some long wires to the LED(s). It is only a protection device and is a bit optional. I have placed this on many of the short-circuit proof LED driver demo circuits to prevent against unwanted destruction of our circuit. If the LED is placed very close to the circuit or with very short wires, then D5 may be removed from the circuit with no penalty in performance or function. However, if the demo circuit is being tested for short circuit protection and the wires used for the LED load are long, the diode prevents the node from falling far negative and prevents destruction. Sadly, on LED driver circuits before this one, some long wires were used during short circuit protection and our 'short-circuit-proof' LED drivers saw unrealistically low negative short-circuit voltages.

    There should be no problems with DC2575A. If there is a problem, please let me know.

    Thanks,

    KSz