Alternative to SN6501

[luky315]

I need a bunch of galvanic isolated voltages (5V, <10mA). A prototype with a TI SN6501 works fine, but I need to synchronize the switching frequency of multiple devices. Is there a syncronizable transformer driver out there?

[T3sl4co1l]

Get a custom transformer with an assload of secondaries?

Or, why not just connect transformers in parallel?

If you need more current, it might be reasonable to tack on some power transistors, or use a similar but alternate method (e.g., just drive the transformers with some transistors arranged in a good old fashioned multivibrator).

Tim

[Frant]

I need a bunch of galvanic isolated voltages (5V, <10mA). A prototype with a TI SN6501 works fine, but I need to synchronize the switching frequency of multiple devices. Is there a syncronizable transformer driver out there?

MAX13253 is similar, but with additional functions. You can choose between an external clock source and the internal one with optional spread spectrum. It has the Enable input, and fault detection/indication.

[luky315]

Thanks. The MAX13253 looks great, but is a bit expensive... A Device like the SN6501 but without ther internal oscillator ("only" the 50% Duty cycle and Break-before-Make part) would be grat...
Has anyone used more than 2 SN6501 (or similar) in close proximity?
I fear to get in trouble with beat frequencys, but I haven't tried it yet.

[Zero999]

Why is it essential for them to be synchronised?

You'll probably find it will work fine just using multiple SN6501s. It's certainly worth building a prototype.

[luky315]

I have bad experiences with unsynchronized converters and high precision circuits...

[Frant]

Thanks. The MAX13253 looks great, but is a bit expensive... A Device like the SN6501 but without ther internal oscillator ("only" the 50% Duty cycle and Break-before-Make part) would be grat...
Has anyone used more than 2 SN6501 (or similar) in close proximity?
I fear to get in trouble with beat frequencys, but I haven't tried it yet.

You may want to consider the DCR01 series from TI (e.g. the DCR010505). It is expensive, but highly integrated (contains the transformer, the rectifier, and the output voltage regulator). Unfortunately, high performance stuff don't come cheap.

[Jeroen3]

They work fine, as long as they are properly decoupled. Even with 4 of them on a board.

You can however go into LT3999 pricing range.

[luky315]

Thanks for the help!
What are your recommendations for generating 2.5kV isolated +-15V (3-5mA is sufficient) and 3.3V (75mA)? I am not looking for the cheapest solution, but for a small and reliable one.

[dom0]

If it's about precision-low-noise things... try a Royer/resonance converter?

[Jeroen3]

Get a recom unregulated power converter brick. And do filtering and LDO afterwards to make it high precision.
http://www.recom-international.com/home.html

Or some other brand. But I'd mostly use recom because they also have some fancy (non-isolated) DC/DC converters as simple smps drop-ins. (9-72V to 5V for example)