Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: yash25 on March 22, 2011, 06:40:05 PM

Title: Isolation via the ADuMxxxx series.
Post by: yash25 on March 22, 2011, 06:40:05 PM

Hi,
I'm working on powering 4 servo motors with a dsPIC processor and I'm supposed to use the ADuM2400 series by Analog Devices to isolate the controller from the servo driver circuit.

Here's the datasheet for the ADuM2400 that I'm using http://www.analog.com/en/interface/digital-isolators/adum2400/products/product.html (http://www.analog.com/en/interface/digital-isolators/adum2400/products/product.html). Now, the PIC works on 3.3volts and my servo control circuit on 5 volts, so I'm basically operating the ADuM under the 3/5 mode as specified in the datasheet.
But in the ratings specified by the datasheet (on page number 7), the maximum "Input Supply Current per channel (Quiescent) = 053 mA".

I'm not sure what this term exactly means. Does this mean that I have to have some kind of a resistor between the input channel pin of the ADuM and the microcontroller pin, with a value such that the sourcing current of the controller falls below this margin (0.53 mA)? Or can I simply connect the Controller's pin to the input channel?

Can someone please help me decipher this?
Thanks!
Yash

Title: Re: Isolation via the ADuMxxxx series.
Post by: waltr on March 22, 2011, 07:11:31 PM

That is the Quiescent (steady state, inputs not changing) needed by the AduM's power pins (Vdd-Vss) per input (1 to 4 inputs). Do read and the notes after the Specs.

Look down further to "Input Currents" for the amount of current needed on an input pin.

I have used these isolators and they work great.
Do note the power consumption with higher switching speeds.

Title: Re: Isolation via the ADuMxxxx series.
Post by: yash25 on March 22, 2011, 07:46:29 PM

So I had a look at the specs and I think it will be okay if I simply connect the pins of my PIC to the input channels right?
It's great to hear that the isolators work well.
I just hope this chip will be able to translate the PWM pulses to my motors faithfully.
Thanks
Yash

Title: Re: Isolation via the ADuMxxxx series.
Post by: waltr on March 22, 2011, 08:16:45 PM

Yep, just connect the IC outputs to the ADuM inputs.

They should be plenty fast for PWM pulse for a motor. I have run 48MHz synchronous data through them.

Title: Re: Isolation via the ADuMxxxx series.
Post by: yash25 on March 22, 2011, 10:28:35 PM

Thanks a lot waltr. Really solved all my doubts.
--Yash