Alternative to SN6501

• Alternative to SN6501
  Posted by luky315 on 22 Jul, 2015 16:07
• 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?
• #1 Reply
  Posted by T3sl4co1l on 22 Jul, 2015 16:42
• 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
• #2 Reply
  Posted by Frant on 22 Jul, 2015 17:18
• Quote from: luky315 on 22 Jul, 2015 16:07

  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.
• #3 Reply
  Posted by luky315 on 23 Jul, 2015 08:22
• 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.
• #4 Reply
  Posted by Zero999 on 23 Jul, 2015 09:27
• 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.
• #5 Reply
  Posted by luky315 on 23 Jul, 2015 10:18
• I have bad experiences with unsynchronized converters and high precision circuits...
• #6 Reply
  Posted by Frant on 23 Jul, 2015 11:09
• Quote from: luky315 on 23 Jul, 2015 08:22

  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.
• #7 Reply
  Posted by Jeroen3 on 23 Jul, 2015 12:13
• 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.
• #8 Reply
  Posted by luky315 on 24 Jul, 2015 10:58
• 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.
• #9 Reply
  Posted by dom0 on 24 Jul, 2015 12:57
• If it's about precision-low-noise things... try a Royer/resonance converter?
• #10 Reply
  Posted by Jeroen3 on 24 Jul, 2015 18:45
• 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)