1. In one of my circuit I need isolated dc-dc converter.
2. Input is 4.5 to 6V & output required is 5V.
I have selected a 9V dc-dc & then will use a linear regulator to generate +5V afterward.

3. I had looked at Murata's NDY0509C , it will do the purpose. But only probelm I see is minimum load current. (55-83mA)

4. My circuit has low power consumption. System remian in sleep for most of time.
5. Does that mean I have to put a resistor to ground at output of dc-dc, so that it can maintain minimum load all the time.
e.g in my case R = 9V/83mA = 108 ohm.

6. Is there any other dc-dc for this purpose I can select

 

Generally yes it means you must put a dummy (ie, power wasting doing nothing) load on the supply if your unit's load is not enough.

However, there are many reasons for a min load to be called out so experimant with your specific supply and unit to see what the supply does at no load. It is quite possible your thing will work just fine with the supply running mostly at no load.

I don't know of an alternative off hand.

 

You need to ask the manufacturer.

However, generally speaking, that is a switching power supply. With those, the lower the current your load is, the less efficient they become. So, with those type of dc to dc converters, it is important to size it correctly so you do not have an inefficient power supply source. That spec is probably there to ensure you are running the converter efficiently.

 

some switching supplies require a load to run. a lot of pc powwer supplies require a small load on the 5 volt output to run no load will allow the switcher to over volage and chut off.

 

Switching power supplies based on transformers usually have a minimum load requirement because you ave to draw energy through the transformer to get it to work as a transformer (love that techy talk). Rarely is this greater than 10% of the rated output for the circuit, and the NDY parts are in that range. Nowhere in your post do you state your actual output current requirement, so it's hard to evaluate your situation and recommend an alternative. Also, what is the isolation voltage you need, and why do you need isolation at all. There are many ways to solve this, such as a 555 driving an audio output transformer. Also, Analog Devices makes amplifiers with isolated power system built-in.

ak

 

I had looked for XP power ITX0509SA.
It says that Minimum Load = 0A.
I will ask the company abt this once.