SN6505B: transformer vendors list

Hi Paul,

Thanks for using our E2E forums.

I understand your concerns.  Sorry we don't have an exact alternative to the transformer #750313734, however for 5V (input) to 5V (output) use case, one can use the  Coilcraft DA2303-AL transformer  (link)  or  the Murata 782485/55C transformer (link) .

The turns ratio on these is a little higher (1:1.5 instead of 1:1.1 ), which means it can work across a wider range of input supply variations, at the expense of a little lower efficiency.  Both designs should work for 100mA current levels without any issues, since the SN6505 has amply design margin on this front (1A capability).  

Now, if you or the customer prefers a closer match for dual-source requirements for production, then one can contact other transformer vendors of choice such as Coilcraft, PCA, Pulse, Halo, Murata etc, to design a custom transformer to meet the end-application needs.  One can ask for the specs desired and the vendors will be more than happy to generate a custom design and provide samples and a quote. usually they can do this is 3-5 weeks (typical, but varies from vendor to vendor)  and we  can help in this process. We also provide a detailed design guide in section 9.2.2.5 of the datasheet to help this process.

Hope this helps, best regards,

Abhi

PS: A quick note on the links shared: These transformer products are generic and known to work across  transformer drivers from TI as well as other vendors. Some of the product pages reference TI and others reference other vendors - just wanted to give you a quick heads-up on the same, so that you can decide how you wish to proceed.

Hi Paul,

Sorry for the delay in my reply.

I compared the two transformer datasheets side by side and here are my comments (using 750313734 as an example reference):

1) DC resistance (DCR) on the 29607 design is 2X higher in the primary and 3X higher in the secondary. This influences conduction losses nad manifests as lower efficiency. However, it is not too bad, because the current levels are low (~100mA at sec , 110mA at primary), so the loss levels are around 10mW on each side. So 20mW loss out of a 330mW load power rating represents about a 6% efficiency delta between the designs [from DCR alone, all else equal]

2) primary inductance and ET products are similar. so this shouldn't be a factor.

3) Core losses: This comes from the magnetic core. Can be a combo of both conduction losses and switching losses. Unfortunately, this is not mentioned commonly in transformer datasheets , including the two we are discussing. So the best way to find out is to get some samples of this and test it out on the customer board.

Because of the low current (100mA) used + moderate~400kHz switching frequency and low Rds_on of the SN6505B , the efficiency will still be decent overall . The exact difference will come down to how different the cores used inside the transformers are.

Does the customer have a specific efficiency budget to meet?