Please let me know external components value of the LTM8050 to meet the folloing spec.
Vin=24V, Vout=-15V, Iout=-2A
I have attached my LTSpice test result. The output voltage drops when the output current is over 1.5A.
You should read the DN1021 - How to Produce Negative Output Voltages from Positive Inputs Using a uModule Step-Down Regulator. ( http://www.analog.com/media/en/reference-design-documentation/design-notes/dn1021fa.pdf )
Iout(neg) =< (1-DCmax) * Iout(pos)Where: Iout(pos) - the maximum output current of ICDCmax = (|Vout|) / (Vin(min)+|Vout|) = (15V)/(24V + 15V) = 0.38462Iout(pos) = 2A (You can see in the datasheet)
=> In this case maximum of negative current = Iout(neg) = (1 - 0.38462) * 2A = 1.23076ABest regardsAdam
Adam is correct, you need a higher current rated part when using a buck for negative output.
When using a buck for negative output, you are using it as an inverting buck-boost. This means that the load current is a fraction of the total current leaving the Vout pin. You can check the Vout pin current in your simulation to verify this is true.
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