# Voltage shifting circuit

Discussion in 'The Projects Forum' started by omicron911, Apr 9, 2010.

1. ### omicron911 Thread Starter New Member

Apr 9, 2010
2
0
Hey guys!

I was trying to build a circuit to regulate the voltage between an ADC to the RS232 port of an FPGA. The voltages outputted by the ADC are at 0V (for logic 0) to 5V (for logic 1). These voltages need to be shifted/multiplied to -6V (for logic 0) to 6V (for logic 1). I was thinking of using a voltage multiplier circuit but I don't know how to shift the voltage from 0-5V to -2.5-2.5V. Can anyone help me? And do you think I'm on the right track?

Thanks,
Anup

2. ### ifixit AAC Fanatic!

Nov 20, 2008
650
118
How fast is the data rate?

3. ### SgtWookie Expert

Jul 17, 2007
22,198
1,797
Gee, why don't you just use a MAX232 TTL to RS232 interface IC?

4. ### omicron911 Thread Starter New Member

Apr 9, 2010
2
0
We have a 1KHz sampling rate. The FPGA already has a MAX232 built in. We were worried about about the ADC logic voltage ranges. If the voltage on the RS232 port is 10V (for a logic 1) or a -10V (for a logic 0) wouldn't it affect the ADC as those voltages are outside the range for the ADC?

5. ### SgtWookie Expert

Jul 17, 2007
22,198
1,797
Ahhh, I don't get what you are talking about.

Your ADC outputs 5v for a logic 1, and 0v for a logic 0, right?

So, why not use the FPGA's internal MAX232 to feed that data out the RS232 port?

Having a circuit diagram and a better explanation of what you are trying to do would be a big help. Otherwise, this is going to be a very long, drawn-out and frustrating thread.