What parameters to look for in selecting D2 and Q1 for 3500 mA backup power?

Question

Which transistor and diode is suitable for fast switching power and low discharge battery when Vin, for PWM 1.2-29 KHz, 4 A, 3.7-5 V?

And which capacitor should be at the output to smooth the switching time?

The LTC4054 is a "Linear Li-Ion Battery Charger". Where does PWM come into the circuit? — Andrew Morton, Commented Nov 28, 2021 at 18:06
So you want to build the circuit more or less as shown but just want to know what Q1 and D2 you should use? What is connected to VOUT doesn't really matter, does it? I am afraid the way your question is written, it sounds like a "shopping" question. Maybe you can rewrite it so you are asking about what parameters to look for in selecting D2 and Q1 instead of asking for a specific part. Maybe that would keep it from getting closed. — user57037, Commented Nov 29, 2021 at 8:37
I do not know which parameters Q1 and D2 are important for this load. If I knew, I would have matched Q1 and D2. What parameters should I pay attention to? — Andre, Commented Nov 29, 2021 at 8:43

Andre · Accepted Answer · 2021-12-01 05:47:02Z

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I've found MCP73871 with 1800mA max output. It's not 3500 mA, but it's enough for me for now.

answered Dec 1, 2021 at 5:47

Andre

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