Other Parts Discussed in Thread: TPS54060EVM-590, , TPS54060, LM5161, LM5017
We use the TPS54060A to generate +-17V from +24V (18..30V). As reference, we used the schematics of the evaluation board TPS54060EVM-590. At about 80% of all devices, the output voltage is stable. I mean if I varry the +24V to +19V, the output does not vary much, and for example only goes down 0.1V from 16.8V to 16.7V. The "good" devices also show not much impact when the current is increased from for example 80mA to 100mA. In contrast, the remaining 20% are very sensitive to the input voltage and also to the current drawn. Some exemplars show only +16.4V at +24V and less than +16V at +19V, so it varies with the input voltage. Therefore the negative voltage goes even more negative to for example -18V and less, I assume the sum stays approx. 34V. For regulation, we first used two resistors at input VSENSE (see the schematics below).
A hint by someone of this forum was to add a third resistor to GND (R99), to balance it out. But also this third resistor did not really help.
We then increased the resistor to the positive side (R40) to bring the voltage up. For example, we incresed the resistor so that a device that shows only +16.4V outputs nearly +17V. The drawback is that the negative voltage goes more negative, but this we think is no problem for us.
Unfortunately, this does not really help, as the devices showing this problem are also very sensitive to the current drawn. If we increase from for example 80mA to 100mA, some examples show a voltage drop of appprox. 0.5V.
Has someone an idea? - Can it be a capacitor that causes this? Or the inductor?