MAX3243: How can I

Helios Yang

Part Number: MAX3243

Hi, My customer would like to know if we could use Ithe pin nvalid (Pin21) to tell if the RS232 signal is there or not? Which setting is proper to use to check this? Also, there is schematic, please help to review if this is correct or not? Thanks

over 7 years ago

0 Helios Yang over 7 years ago

TI__Prodigy 530 points

I was trying to attached schematic but failed. Was checking the table in data sheet P.13. Please help to check and advise how we could attached the schematic for review. Thanks
www.ti.com/.../max3243.pdf

0 Miguel Robertson over 7 years ago in reply to Helios Yang

TI__Guru 62920 points

Hi Helios,

The /INVALID output pin will be low when the input voltage at RIN is close to 0 V (at a minimum, when the voltage is between -300 mV and +300 mV) for at least 30 us. So, it can be useful as an indication that an RS-232 signal is not present.

You should be able to attach schematic files by clicking "Insert Code, Attach Files and more..." and then using the "insert file" button (which looks like a paper clip).

If you try again and still can't attach the file let me know and I can just send you an email instead.

Regards,
Max

0 Helios Yang over 7 years ago in reply to Miguel Robertson

TI__Prodigy 530 points

Hi Max,

Thanks. This is ok and please help to check the schematic.

0 Miguel Robertson over 7 years ago in reply to Helios Yang

TI__Guru 62920 points

Helios,

This schematic looks good as long as R10139 and R10138 are not populated simultaneously. (While this would not necessarily be an issue for the MAX3243, the device receiving the /INVALID signal would see an indeterminate logic level which may be problematic.)

Regards,
Max

0 Su Kevin over 7 years ago in reply to Miguel Robertson

Prodigy 20 points

Hi Max,
I summarize my understandings, if anything wrong, please correct me.
1. R10138,R10139 shall be de-populated since the /invalid pin output is based on RIN. When arbitrary RIN signals level larger than2.7V, the/invalid output would be high. When all RIN signals level close to 0V, the/invalid output would be low.
2. FORCEON(pin23),FORCEOFF(pin22) setting keep 4.7k pull up resistor. These two pins will not impact the high/low level of the /invalid signal.
Thanks

BR, Kevin

0 Miguel Robertson over 7 years ago in reply to Su Kevin

TI__Guru 62920 points

Hi Kevin,

Yes, your understanding is correct.

Max

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MAX3243: How can I