problem in current steer current dac

[huangjw]

hi, all
a 10bit current steer DAC, its 1LSB volatge is 1mV, when i test its DNL with a 6.5bit Multimeter, but output of the DAC will change about 0.5mV.
the Multimeter work well, and there is no clock noise,
so what can induce the large changing upto 0.5mV to the output??
thank you!

 

[erikl]

This is just ½LSB. Don't worry, be happy! ;-)

 

[huangjw]

but if each step change(jump all the time) 0.5LSB, it will influence the acurracy of the final INL and DNL. so what induce the result jump all the time?

 

[erikl]

... so what induce the result jump all the time?

May be the limited resolution of your multimeter?

 

[huangjw]

but the multimeter is good for test other voltage, such as the voltage reference,

 

[dick_freebird]

1-10Megohm meter impedance times bit current =???V

A current mode DAC should be operated into a virtual ground,
like a good quality op amp - input with the feedback resistor
setting a scale factor, and put your meter on the output.

 

[huangjw]

thanks