Issue with dual ADM1278 connection.

Hi Tuan,

    You have correctly observed that when you reverse the drain-to-source bias on FET Q2 the body diode forward biases and conducts current "backwards" from output to input. This is normal behavior. The best way to avoid it is to place two FETs in series in a back-to-back configuration so that when the FETs are off (Vgs = 0) one body diode will always be reverse-biased and no current will flow (actually, there will be some small amount of leakage current).

    Note that the ADM1278 is not the same as an ideal diode (like LTC4412) or prioritizer (LTC4229, LTC4236). You are using the ADM1278 in a way that was not intended, and may or may not be suitable. You can try disabling FET HEALTH checking in the ADM1278's DEVICE_CONFIG[11] register and test the circuit to see if it performs acceptably.

    Check the following article for more information and product ideas that may be more appropriate to what you are doing.

https://www.analog.com/media/en/news-marketing-collateral/solutions-bulletins-brochures/idp-web.pdf

Thanks!
  Nathan

Hi Tuan,

    You have correctly observed that when you reverse the drain-to-source bias on FET Q2 the body diode forward biases and conducts current "backwards" from output to input. This is normal behavior. The best way to avoid it is to place two FETs in series in a back-to-back configuration so that when the FETs are off (Vgs = 0) one body diode will always be reverse-biased and no current will flow (actually, there will be some small amount of leakage current).

    Note that the ADM1278 is not the same as an ideal diode (like LTC4412) or prioritizer (LTC4229, LTC4236). You are using the ADM1278 in a way that was not intended, and may or may not be suitable. You can try disabling FET HEALTH checking in the ADM1278's DEVICE_CONFIG[11] register and test the circuit to see if it performs acceptably.

    Check the following article for more information and product ideas that may be more appropriate to what you are doing.

https://www.analog.com/media/en/news-marketing-collateral/solutions-bulletins-brochures/idp-web.pdf

Thanks!
  Nathan

Hi Nathan,

Thank you for your answer.

Best regards,

Tuan Le

Hi Nathan,

Could you please send a document or guideline to guide for disable FET HEALTH function in the ADM1278's DEVICE_CONFIG[11] register? Because my team said that they tried but they can't disable this function?

Thanks

Tuan Le