Isolation in DC/DC Converters

Hi

I using a 35W DC/DC from Power-One (IMX 35W series).
In data sheet mentioned that it have isolation.

What is isolation and what consideration must be met ?
Should i isolate input from output in PCB too or not ?

Please give me an idea.

thanks.

Isolation is feature, that can be used in your design. If you don't need it, you can still use a common ground for input and output. Or use a converter without isolation, that's typically smaller and cheaper.

isolation(electrical isolation) would be a transformer primary to secondary isolation generally......some environments or regulations require an isolation between the input and output of the power supply.....it is always a feature which you can ignore if not needed.....

FvM said:

Isolation is feature, that can be used in your design. If you don't need it, you can still use a common ground for input and output. Or use a converter without isolation, that's typically smaller and cheaper.

Click to expand...

So what is the best ?
Use same ground for input & output or separate them from each other ?
If i want to separate in from out what consideration must be met ?

Thanks.

It really depends on your application. Isolated DC/DC converters are made, because isolation is often required. A problem with most DC/DC modules is however, that switching frequency interferences are injected between primary and secondary ground, that can spread across your design, if isolation is utilized. It may be really annoying with sensitive analog circuits. A capacitor connecting primary and secondary ground can be useful to "drain" the interferences.

FvM said:

It really depends on your application. Isolated DC/DC converters are made, because isolation is often required. A problem with most DC/DC modules is however, that switching frequency interferences are injected between primary and secondary ground, that can spread across your design, if isolation is utilized. It may be really annoying with sensitive analog circuits. A capacitor connecting primary and secondary ground can be useful to "drain" the interferences.

Click to expand...

Very useful . Can you help me more about separating primary and secondary grounds ?
I must use a DC/DC converter for a precision data acquisition system with a 24-bit Delta Sigma A/D converter.
Thanks.

isolation rating(in Volts) of the transformer used inside depends on the wire isolation material used,primary and secondary wire winding configuration etc....in your case module must be rated for some....so not a concern....

You have to make sure in PCB your power supply input and output sections are isolated by maitaining a clearance distance between the both connections(gnd as well as other.....
for ex 300v it is >4mm like......you can find good articles about clearance rules on the net....

Also like adding a capacitor between isolated GND's will reduce the effective impedance and will help in reducing bothe CE and RE noices....