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# BQ25895: Overcurrent protection for PMID terminal

Part Number: BQ25895

Hi Team,

We are currently designing a portable power bank using the BQ25895RTWR.

The charging current to other devices is supplied from the PMID of BQ25895RTWR, but we would like to know about the overcurrent limitation of the PMID.

I understand that according to the datasheet, the maximum current that PMID can output is 2.4A when the capacitor connected to the PMID pin is 40uF and 3.1A when the capacitor is 60uF.

Qestion1: Is it possible to interpret this 2.4A or 3.1A value as the limit for the output current of the PMID pin?

Question2:Currently our circuit has 47uF connected to the PMID pin. In this circuit, in case the PMID pin is shorted for some reason, what is the maximum approximate short-circuit current that will flow out of the PMID pin?

Our internal other circuit designer explained to me that the overcurrent protection activates at 2.4A, but I understand that is a misinterpretation and would like to know how it actually works.

Regards,

Danilo

• Hi Danilo,

On the BQ25895 since the boost mode output is PMID and not VBUS there is no overcurrent protection. Boost mode will only be exited if boost overvoltage protection is triggered or if one of the battery protections is triggered.

The customer system should use external protection circuitry to ensure PMID current draw is not higher than the boost mode max of 3.1A.

Is it possible to interpret this 2.4A or 3.1A value as the limit for the output current of the PMID pin?

If the customer needs to draw up to 3.1A in boost operation then TI recommends they have 60 uF capacitance at PMID.

Currently our circuit has 47uF connected to the PMID pin. In this circuit, in case the PMID pin is shorted for some reason, what is the maximum approximate short-circuit current that will flow out of the PMID pin?

Can you please clarify your question? Multiple factors such as the load at PMID will dictate how much current flows before boost mode is disabled due to a boost fault caused by the PMID short to gnd.

Regards,

Garrett