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LM74700-Q1: Oring configuration questions

Part Number: LM74700-Q1

Hi team,

Could you please help to check if my understanding about LM74700-Q1 Oring configuration is correct or not.

The power_A and power_B are the same voltage and both exist for two LM74700-Q1. And the output are connected together.

My customer questions:

1. Because LM74700-Q1 doesn't provide fault pin for system to know the status of LM74700-Q1, if rail A turns off because of reverse current protection, how do we know the LM74700-Q1 is turned off and alert system to enable rail B?

2. Do we have suitable solution with input 9~33V max, Iout 45A max, AEC-Q100 application to meet above requirement?

My understanding:

1. For a redundant application, both rails will be enabled if both input exist, and the output will be shared by two rails, correct?

Regards,

Allen

  • Hello Allen,

    1. LM74700-Q1 supports ORing of two power rails with same voltage levels to provide redundancy. However, it does not have a internal mechanism to indicate MOSFET turn off condition during a reverse current protection. An external comparator can be added which looks at Gate-Anode voltage and indicates FET OFF during reverse condition. Gate to anode is 0V when OFF.

    2. LM74700-Q1 is AEC-Q100 Qualified with the following results: 

    – Device temperature grade 1:
    –40°C to +125°C Ambient operating
    temperature range
    – Device HBM ESD classification level 2
    – Device CDM ESD classification level C4B

    If you could share the end application use case, we can suggest a suitable solution.

    Since you asked for AECQ100, does this run directly out of car battery or other? Are the automotive transient immunity required as per ISO 7637-2 and ISO 16750-2?

    3. In a redundant application, both power rails will be enabled if both exist without fault. Output load current is expected to be shared. But the load sharing is possible if both power rails are very close to each other (<15mV or so) and the PCB trace impedance are closely match. Otherwise it might result in sharing error.

    Regards,
    Kari.