Hello Everybody,
I created a circuit that measures some analog sources and decodes some quad-encoders. Its just about to go into production and would'nt you know it the 2" x 2" pcb mount DC-DC converter I was using is going EOL. Now normally I wouldnt care too much and just replace it with another pcb mount DC-DC converter. As it turns out, the DC-DC converter I originally picked has a feature that I need and cant find anywhere else.
The DC-DC converter I was using is this one PTK15-Q24-D5: [url]http://parts.digikey.com/1/parts/731630-converter-dc-dc-5v-dual-out-ptk15-q24-d5.html[/url] and datasheet here http://products.cui.com/CUI_PTK15-Q24-D5_Datasheet.pdf?fileID=4499
The important feature that separates that DC-DC converter from most is: It is a dual output (pos and neg) DC-DC converter with a trim port. The trim port allows you to set the output to a non-standard value. Trim ports are very common on single output DC-DC converters, but I haven't found another one on a Dual (pos/neg) DC-DC conv.
I used it on my circuit to take in 24VDC and output +/- 5.25V. The total load of the circuit is just under 1A. The 5.25V output (instead of a typical 5V) was needed in order for my Instrumentation Amps and ADC to span 0-5V.
Basically I need the overhead for the amps to hit 5V and to be able to use a LDO 5V reference for the ADC.
Just a couple considerations:
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[li]Now, if I could find a drop-in replacement that would be great. If I could find a 1" x 2" sized converter, even better. I haven't found either. [/li]
[li]Its gonna be low volume, so a custom part from another manufacturer is not possible. Its gotta be an off the shelf part.[/li]
[li]I saw some other much higher wattage DC-DC converters with a trim port, but I cant use them. My circuit wont supply the necessary minimum load to ensure voltage regulation.[/li]
[li]I cant add resistors to increase my current usage in order to be able to use the higher wattage converters because the 24Vdc supply feeds multiple circuits.[/li]
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I am gonna keep looking and if anyone has any parts suggestion, I am all ears.
I figured I'd checkout Newark and Element14 for a replacement part. Maybe I just need to look at a different selection of manufacturers.
If I can't find a drop-in replacement my initial inclination is to replace the DC-DC with a linear regulator to create the required +5.25V. Then I would use a small DC-DC converter (buck, inverting) to create -1V.
Note: The negative rail is just so the instrumentation amplifiers can hit 0V.
I would like to hear people's advice on how they would deal with this situation.
Thanks guys,
-Karl