unknown DC-DC chip of SI-9110 differential probe

• unknown DC-DC chip of SI-9110 differential probe
  Posted by teatime on 19 Apr, 2024 09:00
• Hello all,
  
  Right now I have a defective SI-9110 differential probe,
  Input 6Vdc,
  the problem is no -12V, +12V is normal.
  I checked the waveform of Pin15, the PWM of +12v as  attachement.
  But Pin 10 no any waveform.
  If using external -12v instead, this differential probe works properly.
  So the only problem is the DC-DC chip.
  But the factory erase all chip mark.
  
  I have draw the schematic of this part,please see the attachement.
  The length of this chip is 1cm.
  The bottom marked"NBK" and have a "Philippines" mark.
  
  I hope some one can tell me the model of this chip.
  Maybe this chip also used on other type differential probe.
  
  Thanks & Best regards

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• #1 Reply
  Posted by BennoG on 19 Apr, 2024 11:02
• I don't see any feedback divider, so this chip is specifically designed to generate +12V and -12V.
  But I can not find that kind of boost converter controller.
  
  Benno
• #2 Reply
  Posted by coromonadalix on 19 Apr, 2024 14:46
• but feedback pins are 9 and 16 for the ic  ??
  
  if the schematic is ok ?
• #3 Reply
  Posted by BreakingOhmsLaw on 19 Apr, 2024 14:49
• https://www.analog.com/media/en/technical-documentation/data-sheets/max743.pdf
  
  or a clone of that part.
• #4 Reply
  Posted by fzabkar on 19 Apr, 2024 16:18
• https://ae01.alicdn.com/kf/Sf508e8f9f731407b89c61c5a37d4a0d3K/1pcs-lot-100-New-original-MAX743CWE-MAX743EWE-MAX743-SOP16.jpg
  
  https://ae01.alicdn.com/kf/Hf6e06e2bed7e4a59936f710dc9221ce24/100-Original-New-In-Stock-MAX743CWE-MAX743EWE-MAX743-SOP16.jpg
• #5 Reply
  Posted by asis on 19 Apr, 2024 19:43
• Hi,
  
  Here is part of the diagram of the working product.

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  MAX743.pdf
• #6 Reply
  Posted by teatime on 20 Apr, 2024 01:05
• After compare with the datesheet, MAX743 is the right chip.
  Thanks alot for your great help!
   
• #7 Reply
  Posted by teatime on 20 Apr, 2024 01:08
• After remove the chip, then I draw this schematic, it's right.
  The chip MAX743 is the chip I needed.