Hi.

In Ad8403A10 datasheet mentioned that wiper resistance is 50 typical and 100 max.While I'm checking 2 chips and in of them each DAC has 39 wiper resistance and other one has around 44 wiper resistance. I did this test in 0 step. The wiper resistance is so critical in my application.

The question is, is the datasheet mentioned this value for upper steps or average? Does my test method is wrong?

In addition, the step resistance value is changing from first steps and last steps. (for example it is 40 in first steps and it change to 35 in around step 120 and so on . . .). Is it usual? What is the solution?

Best Regards

Hi Koka,

Happy New Year!

1. Wiper Resistance: In the Data sheet it is mentioned that the

typical valueis 50 Ohm. it is not the minimum value.Typical represents average readings at 25°C and VDD = 5 V. Based you your operation condition and manufacturing variations the resistance will be around this value, may be greater or lesser. At the extreme corner condition, the value will be 100 Ohms.2. The full scale resistance should be 10KOhm as there is no 9KOhm part. Therefor 10KOhm/256 steps= 39.06 Ohm for each step. The step resistances changes for various factors. One reason being the as you move up the step the on-resistance of the switches in the internal architecture increases because the Vgs of the Switch increases. On the whole, the step to step resistance can typical change by 1/4 resistance,i.e. 10 Ohms in this case. Please see the DNL specifications in the datasheet.

Regards,

Koushik