Other Parts Discussed in Thread: LM5148, LM5149, LM5143
Hello,
I'm looking for an automotive DC/DC solution with a special load profile: Supply is nom. 48V which need to be converted into 12V. System is always on battery and 12V need to be available all time, so the sleep feature of the LM5148 is what I need. Nominal output current will be <100mA, but in peak (<150ms) 40A need to be provided.
Now I'm wondering if circuit for LM5148 can be designed to be capable for 40A. Lowering the shunt to e.g. 1mOhm would ensure that overcurrent protection will not be active, but according to webbench phase margin will be too low. If I do the same calculation with the excel design tool available for LM5149 (which has the same spec) there is a completely different result with sufficient phase margin in the bode-plot? Which tool is closer to reality?
2nd thought: how does the overcurrent protection work. Does it just limit the current to the max, or is the device switched off for a certaint time / until reset? I did not clearly find out in datasheet. If it's just limiting the output it could be sufficient to design for 20A and buffer the missing pulse with some big capaciy (a Voltage dip of some Volts could be acceptable if output would be designed for 14-15V therefore).
3rd thought: if first two ideas do not work, maybe a two phase design could be feasible, with 20A each phase. There is an example in the datasheet, but only designed for 20A total output. I did not manage to simulate it, as I did not find this topology either in excel nor in webbench and I could not get the spicle model running in our tool LTspice as it shows an error <unknown spice devide type "1" in 17f62b1...>
