Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

5V ADC connect to 3.3V microprocessor

Status
Not open for further replies.

amburose

Junior Member level 3
Joined
Jun 21, 2007
Messages
29
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,498
5v to 3.3v adc

i have a problem ADC0808 connect with 3.3V microprocessor...
what are possible solution...
plz reply urgently....


advance thanks
 

ssss959

Member level 4
Joined
Dec 20, 2007
Messages
68
Helped
6
Reputation
12
Reaction score
1
Trophy points
1,288
Location
INDIA
Activity points
1,600
74lvc level shifter circuit

can i know that is the problem ur facing
 

rajeshkumar123

Full Member level 3
Joined
Dec 27, 2007
Messages
169
Helped
23
Reputation
46
Reaction score
4
Trophy points
1,298
Location
Chennai-India
Activity points
2,124
reduce 5v to 3.3v resistor

hi,

If the port pins of ur 3.3v uP allows open drain outputs ,Configure port pins connected to ADC as open drain and then use pull up resistors to pull the port pins to 5V.
 

joby16

Member level 3
Joined
Oct 23, 2006
Messages
63
Helped
13
Reputation
26
Reaction score
3
Trophy points
1,288
Activity points
1,615
interfacing to a 3.3v adc

Hi Rajesh,

How can you reduce the 5V output of ADC to 3.3V by connecting pullup to 5V. Could you please explain a little more?

Regards,
Joby
 

rajeshkumar123

Full Member level 3
Joined
Dec 27, 2007
Messages
169
Helped
23
Reputation
46
Reaction score
4
Trophy points
1,298
Location
Chennai-India
Activity points
2,124
3.3 microprocessor

Hi,

I suggested o/p pins to ADC be configured as opendrain outputs and i sincerely beleive that giving 5V to 3.3 I/p port might not cause any problem its better to check with ur controller datasheet
 

rikie_rizza

Full Member level 6
Joined
Aug 5, 2006
Messages
339
Helped
29
Reputation
58
Reaction score
9
Trophy points
1,298
Location
Bikini Bottom, between a rock and a pineapple
Activity points
3,173
adc with 3.3 voltage output

If its only data out from 5V system, just use a super cheap resistor divider solution. several KHz can work with this setup.

Trust me, I've done it before.

But from 3.3V to 5V, you should use level translator IC.
 

shortcircuit

Newbie level 6
Joined
Jan 18, 2006
Messages
13
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
1,372
3.3v technik adc

The resistor solution is a good one...
you may also try using a level translator IC like HCF40109
I have done it with this IC and using HCF40109 a working Solution... i have used it for 3.3v <--> 15v

https://www.st.com/stonline/products/literature/ds/2020.pdf

one of our frenz silvio helped me in the past.. i am quoting his message for reference...

-----------
cheers,
ShortCircuit
https://www.rewindPlanet.com

silvio said:
You can try HCF40109.

Containd four level shifting circuits with separately enabled TSL output control.
With two chips you solve your bidirectional transfer for four lines.

HCF40109B, unlike other level-shifting circuits, does not require
the presence of the high voltage supply (VDD) before the application of either the low-voltage supply (VCC) or the input signals.
There are no restrictions on the sequence of application of VDD, VCC, or the input signals.
In addition, there are no restrictions on the relative magnitudes of the supply voltages or input signals within the device maximum ratings;
VCC may exceed VDD, and input signals may exceed VCC and VDD.
When operated in the mode VCC VDD, HCF40109B will operate as a high-to-low level-shifter.
On low-to-high level shifter each circuit will shift a low-voltage digital-logic input signal (A, B, C, D)
with logical 1 = VCC and logical 0 = VSS to a higher voltage output signal (E, F, G, H) with logical 1 = VDD and logical 0 = VSS

If the current is not an issue :

https://www.st.com/stonline/products/literature/ds/2020.pdf
 

apv1965

Junior Member level 2
Joined
Feb 25, 2008
Messages
20
Helped
1
Reputation
2
Reaction score
0
Trophy points
1,281
Activity points
1,405
adc 5v

If you are feeding ur controller the out put of Ur ADC, then do following:
1. check the data sheet of microproccessor for the iput pin compliance for 5 volts. Normally they allow but checkingis must for safty of ur Processor. If it is there the Use it directly without worry
2. If they are not 5 volt compliant then U can do either resistor networking or Level translators. If the processor is critical and the circuit is more critical then I would recommend you to use level translators always. It is more safer and not too much expensive also...

If you need some numbers of level translators U can visit TI site or Maxim site or ST site or NXP. there ar elot more...
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top