MAX3232-EP: 1uF caps for C2/C3/C4

Jay G

Prodigy 140 points

Part Number: MAX3232-EP
Other Parts Discussed in Thread: MAX3232

Hello,

We currently have 1uF caps populated in a design for C2/C3/C4 instead of 100nF caps. Is this an issue?

Thanks,

Jay

over 7 years ago

0 Wade Vonbergen over 7 years ago

TI__Guru 62930 points

Jay,

Please refer to this post. It discusses the cap values and performance.

If this answers your question, please click "Verify it as the answer"
Regards,
Wade

0 Jay G over 7 years ago in reply to Wade Vonbergen

Prodigy 140 points

Thread helps but seems to imply 1uF ok for c2/c3/c4. I am seeing tx errors ( garbled serial port output) at high temps around 80c. Rx still works at high temps and tx will begin working as I lower temp. Device is in a fixture which is difficult to probe. We plan to disassemble and try 100nf caps for all but would like to know if there is areas on the 1uF would cause to fail. Our vcc is 3.3v.

0 Wade Vonbergen over 7 years ago in reply to Jay G

TI__Guru 62930 points

Jay,
I am checking with some experts for additional advice.
However, maybe you can provide a few more details.

Is this occurring on more than 1 board? Is this new design?
How is temp measured? Is this predicted die temp, or ambient. Power can be estimated from information in this post: e2e.ti.com/.../695315

Thanks,
Wade

0 Jay G over 7 years ago in reply to Wade Vonbergen

Prodigy 140 points

Wade,

It happens intermittently on 2 boards and is a new design. Temp is just ambient temp.

Thanks,

Jay

0 Ron Michallick over 7 years ago in reply to Jay G

TI__Guru**** 167546 points

Hello Jay,

You should be able to get a short cable extension that you can cut up to get to the RS-232 TX and RX signals.
What type of connector is used? For DB-9, DB25, RJ45 there should be breakouts boards readily available.

It is very important to see the suspect TX line. Ideally I 'd like to see V+ and V- pins on the MAX3232.

0 Jay G over 7 years ago in reply to Ron Michallick

Prodigy 140 points

Ronald,

I will try to at least get TX lines. Do you see a potential issue with the 1uF caps, or should these work fine? I assume the datasheet recommended values of 100nF would be preferred correct?

Thanks,

Jay

Interface

Interface forum

MAX3232-EP: 1uF caps for C2/C3/C4