MAX232 - Intermitent communication

Jose Fernando Ribeiro do Val

Other Parts Discussed in Thread: MAX232

Hi,

We are having trouble with MAX232 s/n 08AX49KG4. We are mounting in a typical operating circuit, pointed in figure 4 of Texas datasheet.
The problem happens intermittent and not in all ICs.
We put the osciloscope in the pin 1 of the problems ICs and the wave period were around 1,2 uS, while the no problem ICs were 12 uS.

Can anyone help me?

over 12 years ago

0 Ron Michallick over 12 years ago

TI__Guru**** 166006 points

Jose,

Can you provide a failing waveform?
Do all the of the C1 and C2 pins also run at 1.2uS?

0 Jose Fernando Ribeiro do Val over 12 years ago in reply to Ron Michallick

Prodigy 60 points

Hi Ron,

We attached a file with the waveforms.

You can see that both pins run at 1.2 uS.

Best regards

Signals.zip

0 Ron Michallick over 12 years ago in reply to Jose Fernando Ribeiro do Val

TI__Guru**** 166006 points

Jose,

The signals look good other than their frequency. There is no frequency specification for the MAX232, but this is much faster than expected. There is an internal RC oscillator in the MAX232. If the capacitor value was bad then the TOUT slew rate would also be very fast (miller cap also low value). I will look into the date code you provided.

Can you explain the intermittent nature of the problem?

0 Ron Michallick over 12 years ago in reply to Ron Michallick

TI__Guru**** 166006 points

Jose,

No anomalies were found for that date code.

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MAX232 - Intermitent communication