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I need to take power from ebike's battery (30–60VDC) for a datalogger (3V3) based on STM32 with almost no consumption.

My question is what is the most efective conversion from 60V to 3v3?

Is it good to use one DC-DC Converter from 60V to 3v3 or is it better to use more converters for example from 60V to 12V and second from 12 to 3v3? Maybe there is any better solution...?

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    \$\begingroup\$ I would just power it from a separate battery pack. Cheaper and easier. Make sure to have common ground though. \$\endgroup\$ – Eugene Sh. Nov 17 '20 at 16:24
  • \$\begingroup\$ A single buck converter will do the job. Just make sure to get one that is rated above your max voltage to give you some margin. LM5163 from TI is a nice one that goes up to 100V input. \$\endgroup\$ – Aaron Nov 17 '20 at 17:31
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I'd use a buck converter direct down to 3.3 volts but, if the data logger is something valuable then I would also use a protection circuit so that if the buck converter went belly-up, the protection circuit clamps at (say) 3.6 volts or whatever is the upper limit for the data logger. It's called a crowbar circuit and it can be a useful insurance policy. Because a crowbar is also a shunt regulator it would do nothing until called-into action by the failing buck converter. You'd also need a fuse so that if the buck went short circuit, a gazillion amps wouldn't flow into your logger/crowbar circuit.

You'd probably decide to use a fuse anyway as a fire risk precautionary measure.

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Just use one buck converter that supports your input range and desired output voltage. Buck converters have a relatively high efficiency and should therefore be suitable for your application.

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I would consider using an isolated DC-DC module.

You can get a 6W DC-DC Mornsun converter that will handle 18-75V input (80V max) for around $7 USD in one-off.

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60V to 3.3V is on the upper of how much you can step down with a single buck. But if you can find one, there really is no reason for multi-stage conversion if you don't need any intermediary voltages. It would just introduce extra complexity (and potentially other issues such as beat frequencies).

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