LTC4416 Power ORing

Hi,

I am doing a project of dual power input and single output, with max load current 30A. The 1st input is 24V from ACDC supply, and 2nd input is battery with voltage around 23V to 28V.

In our case, fixed DC input has higher priority, when DC input is lost, battery will supply the load. When DC input is within 24V +- 1V tolorence, the battery will not supply the load.

Based on LTC4416, it is similar to "V1 less than V2" mode, but in low batt case, V1 could be higher than V2.

Currently there are 2 design options:

Option A:

E1 is set at 1.35V when V1 is 24V (R divider by V1), and E2_N is set at 1.25V when V1 is 24V (R divider by V1). This means When V1 is <22.2V, E1 is < 1.25V.

 

Option B:

E1 is pull up to V1 permanently, and E2_N is set at 1.35V when V1 is 24V (R divider by V1). That means when V1 is <22.2V, E2_N is < 1.25V.

 

Option A is from my colleague, but I am thinking it will operate like the following:

a) When 22.2V < V1 < 24V, E1 > 1.25V (High) and E2_N< 1.25V (Low), that mean both paths are ON, i.e. load sharing mode.

b) When V1 > 24V, E1 > 1.25V (High) and E2_N > 1.25V (High), so path 1 is ON and path 2 is OFF.

c) When V1< 22.2V, E1 < 1.25V (Low) and E2_N < 1.25V (Low), so path 1 is OFF and path 2 is ON.

That means case a) is not function as power prioritizer.

 

For Option B (follow “V1 less than V2” mode), V1 is always power the load except it is lower than allowed operating voltage (24V+-1). When V1 is >22.2V, E2_N is > 1.25V so path 2 is OFF. When the external AC power is lost and V1 drops below 22.2V, E2_N is < 1.25V so path 2 is ON.

 

What is your opinion and comment?

 

And I find LTC4418 power prioritizer is also possible for our case, but I am not sure if I choose external P-FET that is ok for 30A continuous operation, whether it is ok for LTC4418 to operate as expected.

Thank you.

Regards

RF Yan

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