MAX3232 no data on R1out

Valentin Popa

Other Parts Discussed in Thread: MAX3232

We have a MAX3232 that works fine on T1Out pin and I see the data properly on the PC.

However, the data sent from the PC on R1In pin will never show on the R1Out pin. I see the data on R1pin (attached) which looks fine to me.We have same issue with 2 boards.

Vcc is 3.3V and all C1,2,3,4 and Cbypass are 0.1uF. C3 is connected to Vcc instead ground but that is acceptable according with the datasheet.

What could be issue?

Valentin

over 9 years ago

0 Ron Michallick over 9 years ago

TI__Guru**** 164876 points

Valentin,

That is very odd. What is on the ROUT pin, 0V, 3.3V or some other value?

The receiver should work even if the charge pump caps were missing.

V+ cap to VCC is fine usage.

I see two boards are bad, are many more good?

0 Valentin Popa over 9 years ago in reply to Ron Michallick

Intellectual 680 points

Ron,

On R1out (pin 12) there is 3.3V. I checked and there is no short to 3.3V power supply.

We have only two boards and both of them behave the same.

Valentin

0 Ron Michallick over 9 years ago in reply to Valentin Popa

TI__Guru**** 164876 points

Valentin,

Was the input signal from first post taken at pin 13, RIN1?
Is it possible that pin 13 isn't soldered down to the board?

Is the other receiver working (pins 8,9)?

Can you measure the voltage at VCC, V+ and V- pins [16, 2, 6]?

0 Valentin Popa over 9 years ago in reply to Ron Michallick

Intellectual 680 points

Ron,
Yes, input signal from first post was taken at pin 13, RIN1. We double-checked and all pins looks solder pretty good (the board was built by an assembly house). We reworked all the pins but we still have same behavior - data on pin 13 but no data on pin 12. Pins 8, 9 are not used in the design and are not connected to anything.
The voltages at pins 16,2,6 are +3.3V, +5.9V, -5.6V.
Valentin

0 Valentin Popa over 9 years ago in reply to Valentin Popa

Intellectual 680 points

Ron,
We re-flowed everything with hot air and started to work now!
Looks like there is an assembly issue with both of the boards.
Thanks for your help,
Valentin

0 Ron Michallick over 9 years ago in reply to Valentin Popa

TI__Guru**** 164876 points

If you are using only one driver, the unused DIN should be connected to ground or VCC.

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MAX3232 no data on R1out