Formula for calculating DAC output

[graciousparul]

Hi,

The logic levels used in a 6-bit R-2R ladder DAC are 0=0v and 1=+5v.What is the binary input when the analog output is 4V?

Thanks in advance...

 

[laktronics]

Re: DAC

Hi,
(4÷5)64 in binary.
Regards,
Laktronics

 

[Asif2008]

Re: DAC

i think major are saying right

 

[graciousparul]

Re: DAC

hi laktronics,
Can u say me is this standard formulae of just...?
Thanks

 

[muralicrl]

Re: DAC

Hi friends,

The standard formula for calculating the DAC output is, for example of 6 bit DAC

Output of DAC in Volts =
((32*D5 + 16*D4 + 8* D3 + 4*D2 + 2*D1 + 1*D0)*SUPPLY VOLTAGE)/(2 POWER 6)

Thats all.

All the best,

N.Muralidhara

 

[H_D_R]

Re: DAC

hi laktronics,
Can u say me is this standard formulae of just...?
Thanks

see the attached jpg.

hello laktronics you also check it and please let me kno is it true or false..??

Thanks you..

 

[laktronics]

Re: DAC

Hi H_D_R,

The equation given by you is same as that given by Mr Murali as shown below:

Vo = KRf ( A1/2 +......+ A8/256) ----(a) ; where A1..A8 is a binary number

From the above equation,

Vref = KRf (1) ----(b) ; (A1/2+... +A8/256) =1 since for Vref A1 to A8 all are one.

Dividing (a) by (b),

Vo/Vref = (A1/2 +.....+A8/256)

Multiplying both sides by 256,

(Vo/Vref) 256 = (128.A1+64.A2 +......+ A8 ) ....(c) which is same as Mr.Murali's
eqtn. applied to a 6bit DAC.

The above eqation (c) will be valid for unipolar DACs.For bipolar offset binay DACs also it will hold good if you take Vref as total span of -Vref to +Vref.
The equation also applies to similar ADCs if you replace Vo by Vin.

Then there are sign magnitude and 2's complement codes for which +ve and -ve outputs are coded separately.

Regards,
Laktronics

 

[H_D_R]

Re: DAC

yes, i knew that laterly...

bt i think this will make more clear to my friend "graciousparul".

thats it...