I have a problem with my MAX232 chip and can't find the solution. The schematic of the chip is in the attachment. The chip is soldered on to a PCB.

I've checked all the connections, the supply voltage and the grounding. The supply voltage is a steady 5V signal and the ground pins of the caps and chip are correctly connected so I'm guessing that isn't the problem.

The strange thing that I found out is that the VS+ pin is 4,5V and the VS- pin is 0V instead of the 8.5V and -8.5V according to the datasheet.

How can this be possible or is the chip burned?

Thanks in advance.


  • \$\begingroup\$ datasheets suggests smaller capacitors. although it doesn't seem to be the problem \$\endgroup\$ – Gregory Kornblum Jun 15 '18 at 9:29
  • \$\begingroup\$ Are you using polarized capacitors and connecting them backwards? \$\endgroup\$ – Michael Karas Jun 15 '18 at 9:33
  • \$\begingroup\$ Circuit looks fine. Check for shorts between pins due to soldering. \$\endgroup\$ – Andy aka Jun 15 '18 at 9:33
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    \$\begingroup\$ If this is a Maxim MAX232, then Maxim Integrated tech support can help. If it's a defective chip or a counterfeit being sold with Maxim's brand mark then Maxim will definitely want to investigate. (note: I am a Maxim applications engineer) Output T1OUT should definitely not be grounded, that would explain the charge pump being undervoltage. Can you lift pin 14 from the PCB and confirm it really is an internal short to ground? \$\endgroup\$ – MarkU Jun 15 '18 at 20:31
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    \$\begingroup\$ This is a chip from Texas Instruments. Before the weekend I ordered some new ones. If soldering a new chip on the footprint doesn't solve the problem, I will definitely contact Texas Instruments to find out what is wrong. \$\endgroup\$ – Matthijs Huisman Jun 18 '18 at 6:23

I solderded a new IC on the footprint and my application is working again. The chip somehow must have been damaged due to wrong voltages or ESD I think.

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