interfacing Max232 to FPGA(IMP)

[Navya]

max232 fpga

We need to interface Max232 to FPGA. FPGA's supply voltage is 3.3v and for max232(Texas Instruments) in their datasheet it is specified that " input supply voltage range is -0.3v to 6v.

Can we connect the T1in and R1 out pin of max232( working at 3.3v)to FPGA?
will max232 work at 3.3v?

please reply at the earliest

 

[thuyet]

fpga max232

dear Navya
You can connect T1 and R1 to FPGA. I made it before It worked fine.But you shoul have a power sypply for max232. if on your fpga board have 5v power,you can use it to supply power to max 232
good luck

 

[Moriarti]

max232 3v3

Hi,
There are a lot of RS-232 Transceivers with work under 3V3 Supply. 64 type produced by MAXIM, more than 11 by Ti. MAX3225 - 1µA Supply Current, 1Mbps, 3.0V to 5.5V, RS-232 Transceiver with AutoShutdown Plus **broken link removed**, or SN75C3243 from TI http://focus.ti.com/lit/ds/symlink/sn75c3243.pdf. Power Supply for both are 3V3 and you can connect directly TxD , and RxD to FPGA (in corret side of converter-Logic).

 

[Navya]

max3232 imp

Hi,
there is 5v power supply for max232. but my doubt is that if "Rout" of pin from max 232 will be of 5v? can we give it directly to fpga working at 3.3v?{Max232 from TI)

 

[mta97e]

max3224 fpga interface

there is 5v power supply for max232. but my doubt is that if "Rout" of pin from max 232 will be of 5v? can we give it directly to fpga working at 3.3v?{Max232 from TI)

even Rout is 5v, i think FPGA can live wiht it.
Defing the FPGA I/O standard to 3.3V at input doensnt mean that the input voltage to that pin is limited to 3.3V. But the signal will be clipped if it higher than FPGA supply volatge.

I think the pin can takes up to 5V which is the supply voltage of FPGA.

There are 3 supply voltages to teh FPGA. I am not sure which one.
Check the data sheet.

 

[Navya]

3v3 max 232

Among the 3 voltage supplies of fpga our maximum limit is 3.3v. we are using spartan3 FPGA where vcc is 3.3v

 

[tlp71@hotmail.com]

max232 3.3v transeiver

i suggest you to use also the spefied condensators on multipliers pins of max232

 

[Navya]

max232 working

Do i have to go for max232 which works on 3.3v?

 

[Iouri]

no, supply voltage is usually from 2.7V to 5V

 

[Navya]

Re: interfacing Max232 to FPGA(IMP)plzzzzzzzz

But the " R1 out" pin of MAX232 which is connected to fpga will be of 5v itself no? which can damage fpga whose maximum voltage is 3.3V.


Anyone plz send me a solution

 

[Iouri]

nop, because you power up your max chip from 3.3V

 

[mta97e]

have a look at

**broken link removed**

hope it helps

 

[Navya]

so "R1out" will be 3.3v? sure?

 

[Iouri]

yes!!!!

 

[Navya]

Hi Iouri,
Please read this from xilinx site that spartan3 is not 5v tolerant....

"When the input voltage is greater than VCCO +0.5V, the upper clamp diode turns on and conducts a reverse current into the associated supply (VCCO for nondedicated I/O; VCCAUX for dedicated I/O). Because this reverse current can damage the I/O, the Spartan-3/-3E I/O is not 5V-tolerant."

 

[Iouri]

OK where +5V will come from, if you power up max chip from 3.3V rail?

 

[Navya]

will max232 work with 3.3v supply then??? In its data sheet it is specified that the recommended voltage range is min 4.5v. ie y i m so confused. Have u tried max232 with 3.3v??

Added after 16 seconds:

will max232 work with 3.3v supply then??? In its data sheet it is specified that the recommended voltage range is min 4.5v. ie y i m so confused. Have u tried max232 with 3.3v??

 

[mta97e]

hi ,, there are alot of 232 transiever wiht 3.3 supply.

Either u use 3.3V transeiver or you can use 5V transeciver resistor to cope wiht the 3.3V of the FPGA.
Or you can integrate the 232 funcation inside the FPGA. I believe there are free source code for UART core..

 

[Iouri]

I don't think it should be a problem, but you can always use somethink like this it has same pin out as max232

https://focus.ti.com/lit/ds/symlink/max3232.pdf