DAC Output for input from 0000..00 to 1111...1

[bgpradeep]

Hi All,

Can anyone help me on why the DAC output is behaving as shown in the attached file. I have also attached the zoomed part.

The simulation was run for 200US and the Clock was 10MHz.

Thanks

 

[fun.zhao]

maybe you need input a signal tone signal and do fft for it

 

[echo47]

Is this suppose to be a 12-bit DAC? It looks like the lowest bit isn't doing much, the next four bits are inverted, and probably more problems.

 

[bgpradeep]

Its actually a 10-Bit DAC

Added after 59 seconds:

Is it a problem with the input i am providing? or some logical mistake

 

[jacobliu]

current mode DAC?

 

[mady79]

I think its a good idea to get a ideal ADC out put and give this ADC output as an input to the designed DAC .plot actual analog input given to ideal ADC and DAC output and see the difference .

Curve looks strange ,but there is a monotonic behavior through out .traingular like step every 32 cycles and with in this triangular wave decreasing output step at half the expected clock period .

If u can provide above requested plot then its easier to look in..
hope this helps

 

[bgpradeep]

Thanks for the replies. I have attached the output for a sine input fed through A/D to the D/A. I am not getting why there is an inversion at the start and at the mid point.

Thanks
Pradeep

 

[echo47]

The inversion looks like the most-significant bit is inverted. That's a common error when mixing signed and unsigned values.

 

[mady79]

I think you have to check ideal ADC output first , some issues at Vin=0.5V ,check if the IDeal ADC outptut bits for Vin <=0.5V .

Hope this helps ..

 

[bgpradeep]

I inverted the MSB bit and found that my output is following the output but the value is around 1.5V (input was 1V). What might be the reason for this. Can this be because of MSB current sources not generating the exact value of current.

I have attached the output got after changing the MSB bits.

Thanks

 

[artem]

You have a DAC's reference voltage and you can change it . Give input to your ADC let say 1 V then adjust reference voltage on DAC so it becomes 1 V also. Or if you dont like to touch reference , calculate coefficient Vin/Vout (Vin to ADC Vout from DAC) then multiply this value to ADC value and you will get whatever you got at input (of course rounding error can influence your output).