Hi there evrybody,
I have recently ordered few MAX232N for a custom board whose function is to converter from RS232 to RS485 communication standard. While testing the behavior of the board, we encountered some complications. In order to check what was going on, we replicated the "Typical Application" design reported on the MAX232N datasheet for the power part of the component and tested it on a breadboard (we used electrolytic capacitors of 1 uF as reported in the picture below).
In this condition, when powering the system for the first time, it absorbs more than 400 mA, the chip gets hot and does not work as expected; if the power is switched off and then turned on again it behaves properly. We have been doing this boards for at least one decade now, and this is the first time we encountered this type of issue.
In the following, I report the images of the oscilloscope when checking the output of port 1 (C1+, yellow signal) for the MAX232N, product number: 21AJ46M
and for an "old" order: MAX232N, product number 35A8XCK.
With product number I refer to the identification code physically reported on the chip itself, above the name/identifier.
As you can see, the frequency of this signal is 10 times bigger with the newest ordered chips (around 400 kHz for 17AJ46M and 21AJ46M), while with the older purchase (88CR54K, 35A8XCK, 66HXYJK) it is around 40 kHz.
I believe this is related to our problem with the power consumption/malfunctioning of the chip when following the "Typical Application" design reported above. Do you have any advice on how to fix/solve this inconvenience? Is it normal this change of frequency for this "new" versions?
Thank you for your help,
Best
Davide F.
