Other Parts Discussed in Thread: TPS54040
Hi Team,
I have a customer who is trying to build an inverting buck boost with the TPS54040A and is having some issues with it:
(Vin = 15V, Vout = -5V, 1.5MHz switching frequency)
-5V runs without load, but with a 12 ohms resistor (417mA load) the voltage breaks down after around 10 seconds. This could be something thermal although after rough calculation with the datasheet parameters I do not see how the junction temperatures can reach 180 ° C.
In Application Report SLVA317B in equation (5), Dmax is included in the Iomax calculation - can you explain that to me? With 110mA ripple I might be pretty much on the limit of what is acceptable.
When I remove the load, the voltage does not come back. I have to turn Vin on / off. After I short the capacitor on the SS the voltage recovered (without load).
So summarized-
Can you explain why Dmax has to be taken into account for negative voltages of the maximum current calculation? Do you have an explanation why the -5V Buck circuit does not recover from an overload. And how can I fix it?
Circuit diagram of the -5V circuit is attached.
