TRS3232: External diode

K.Hamamoto

Part Number: TRS3232

Our customer are considering to add the external protection diode to RIN1/2 and DOUT1/2 pin.

I understand the benefit of this device is having ESD protection internally.

On the other hand, I am concerned how to connect the external diode. In generally, the protection diode is connected to between VDD or GND.

Is that possible to connect that diode between V+ or V-?

( DOUT1/2 or RIN1/2 ~~ "diode" ~~ V+ or V-)

Best Regards,

Koji Hamamoto

over 5 years ago

0 Hao L over 5 years ago

TI__Mastermind 25705 points

Koji,

You need bidirectional diodes for RS-232 bus pins, since the signal swings from positive to negative. You can look at the page 5 of this note for the idea. This blog also shows how to choose TVS diodes to work with IC.

Please let me know if you have more questions.

Regards,

Hao

0 K.Hamamoto over 5 years ago in reply to Hao L

Guru 12155 points

Hi Hao,

Thank you for your support.

I understand it is a typically method to add the diode by referring the note you recommend. On the other way, can we add the diode between charge pump output V+(or V-) and bus pins?

Best Regards,
Koji Hamamoto

0 Hao L over 5 years ago in reply to K.Hamamoto

TI__Mastermind 25705 points

Koji,

The ESD charge needs a path to return to the ground. Neither V+ or V- has solid path for such current flow. Please let me know if it makes sense to you.

Regards,

Hao

0 K.Hamamoto over 5 years ago in reply to Hao L

Guru 12155 points

Hi Hao,

That's make sense. Thank you!
Our customer are going to add the diode between bus pins and V+(V-). So,we need to explain to change the connection.

Best Regards,
Koji Hamamoto

0 Hao L over 5 years ago in reply to K.Hamamoto

TI__Mastermind 25705 points

Koji,

I'm glad I could help. Please let me know if you get more questions.

Regards,

Hao

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TRS3232: External diode