Can I use TOP249YN in place of TOP248YN

Posted by: w.andless on 03/08/2013

Hello, I have a SMPSU that has failed. It has a TOP248YN with obvious damage, (and some other failures diodes etc) but I am having trouble obtaining replacement, can I use TOP249YN which seems readily available?

If not can you suggest another part to replace TOP248YN?

Thanks

Comments

Sir,

Is this your own design or is this a PSU that was purchased from a vendor? The TOP249Y can be used as a replacement for the TOP248Y, however, the current limit would need to be matched to that of the TOP248Y.

Thanks for the reply, no its not my design its a PSU that is fitted to a rack mounted server monitor, which I am repairing. If I installed a TOP249YN would I need modifcations to the circuit to accomodate ?

Regards

I would first look at the X-pin on the device and ask the following questions:

1. Is the X-pin connected to the S-pin of the device?

-OR-

2. Does it have a current-limiting resistor as shown in fig.28 of the datasheet for the TOP-GX device?

In case of 1: No current-limiting is used and the TOP248 is configured to operate at the full current-limit.

In case of 2: The device is current limited.

In case you wish to replace the TOPSwitch only (keeping everything else on the PSU as before), then you will have to match the current limits for the two devices using an appropriate current limiting resistor (refer fig.52b of the datasheet).

TOPSwitch-GX Datasheet:

http://www.powerint.com/sites/default/files/product-docs/top242.250.pdf

Hello, there is a 14k resistor between the pins, so it is current limiting. I will try harder to obtain the TOP248YN, as I am concerned that making modfications to the circuit could make it prone to failure!

Thanks for your help.