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An application requires a -5 V negative power supply with max 550 mA. I can't find a reliable dedicated positive to negative converter for such currents in the market at a reasonable price.
I came up with this DC-DC converter and here is the datasheet.
Can I just ignore the +Vout and only use -Vout for a circuit which requires -5 V and max. 550 mA where ambient temperature will not exceed 40°C? And if I use an op-amp with such a negative supply should it be dual type?
If a DC-DC module is isolated, then you can convert a positive output into a negative output by simply connecting the positive output pin to GND:
This is why you wont find isolated modules that specify they are positive in, negative out. Because they can be either.
The part you link to is indeed isolated, so you could use say TEN 8-1211 in the configuration pictured on the right to get a negative output (connect +Vout and -Vin to GND, giving -Vout as -5V).
Given you only need ~3W, lower power and smaller isolated DC/DC modules with regulated 5V output are readily available (e.g. TDN 5-2411W).
You can. But some modules needs extra minimum load.
Some dual output power supplies are unstable when leaving one side as open. For a little more detailed information, check this FAQ About DC-DC Converters article. Thus, you may need to connect some load resistor to the unused positive side.
Check the datahseet of your DC-DC module carefully. There might be minimum required load current for stable operation.
I have no expeirence with your specific model, but with some other dual supply modules. To use TDK +/- 12V DC-DC modules, I should connect 100 ohm / 3W resistor for +12V to use -12V. If not, I got + 13.5V / - 10.5V.
To address the second part of the question, any single-rail op amp can be used with a negative supply. Conceptually there’s a 5V difference between the two rails, one is designated as ‘ground’ and the other as relative to ground. Within the circuit the components don’t (for many purposes) know or care which rail is ground, they only see the voltage differences. So as far as the op amp and other components are concerned, you can use a positive-rail circuit but connect the positive rail to ground.
