Calculation of 4.7k pull-down resistor 6052e? ref.pg.3-313 of dio-96 manual

[ennis]

6052 dio powers up in input high imped state. you add 4.7 k resistor to pull down. I want to understand calc. of this value. I am using as a ref. pg. 3-313 of pci-dio-96 manual, and repeating for 6052e, but am not getting correct value. Need an explanation.

[rgharrison]

Hi,

A couple differences are that the internal pull-up resistor is 50k ohms, and we are assuming negligeable leakage current. If we make the same assumption as the manual about using the largest resistor value that will create a voltage of 0.4V, we should get 4.3k ohms.

Typically, any value around this range should work as the internal resistance has an error tolerance and there also will be leakage current. I also believe that 4.7k ohms is a standard resistor value for digital signal conditioning and board development and that is why that value is chosen as opposed to 4.3k ohms. Anyway, hope that helps. Have a good day.

Ron