MAX3221E: MAX3221E Functionality Problem

Hi Tirthal,

I think your setup is correct for normal operation (FORCEON=FORCEOFF bar=H, EN bar=L). How did you measure the C1 and C1 voltage? If the device is powered on, it might be easier to check V+/V-. V+ should stay around 5.5V and V- around -5.5V. You can refer to this article for the V+ waveforms.

e2e.ti.com/.../how-the-rs-232-transceiver-s-regulated-charge-pump-circuitry-works

If V+ and V- look good, that means the charge pump works. You can send TTL logic (from MCU) to DIN and expect RS-232 signaling from DOUT. On the other hand, RIN takes RS-232 signal and converts them to TTL output by ROUT.

Please let me know if it makes sense to you. Let me know if you have more questions.

Regards,

Hao

Dear,Sir

Thanks for the response,Some minor shorting were found in our setup in which by mistake the dout pin was shorted with the 3.3v Pin.

The voltage i am getting after fixing the setup are mentioned below :

1)Pin 3 - V+ = 4.85 V

2)Pin 7 - V- = -4.95 V

3)Pin 2 - 4 - C+ / -C-  = 2.4 V

3)Pin 5 - 6 - C+ / -C-  = 4.96 V

4)Invalid = High = 3.3 V

When i am manually providing the input on the Din Pin 11 (3.3v), the Dout Pin 13 is showing (-4.9 V).And  Din Pin 11 (GND =0 V ), the Dout Pin 13 is showing (4.9 V).

I tried to communicate withe rs232 to UART Dongle and provided some input on the Pin 9-11 i received the output from the Pin 8-13,So i think the IC is functioning properly.

Please suggest any other thing while dealing with the level shifter IC,If any.That would Help Us. 

Tirthal,

The measurement results look good to me. The only note is that voltage of C1 and C2 pins toggle during charging cycle. The DC value may not mean much.

What kind of level shifter do you need? If you want to interface with 1.8V logic, TRS3122E or TRS3253E can be considered.

Regards,

Hao

Dear.Hao L

I would like to ask you one more question that ,what is the purpose of the Invalid Pin,As per the datasheet it s[specifies that it is a logic line. correct ?So it doesn't need to be powered correct..?

In our Schematic if you see we have kept the invalid pin as Unconnected.

In our setup in which we are performing the testing when i keep the invalid pin high 3.3v i am able to receive the output.

But if i keep the invalid pin as unconnected then i am unable to establish the communication.Can you please specify whats the reason behind that.

The LCD Which we are communicating is having the same IC MAX3221E implemented in it which have logic levels of -5.5 v and +5.5 v.

Please help  on the above mentioned Query..!!

Dear,Sir

Apologize for the delayed response...!!

I rebuild the whole setup and was working fine,So i think problem was in the setup the was custom made.

Regarding the invalid pin it is showing the logic levels of 3.3 V and 0 V depending on the valid input on the Rin Pin of the IC.

Have a nice Day..!!