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Answered

PWM to control small load

mtanguay 4 months ago in Master modules / MC4x updated by Gustav Widén (System support) 4 months ago 1

Hello,

We are currently working with a MC43, and I had a question regarding the use of PWM out as a control device. I found this post, since it was 4 years old thought I would ask again. We are trying to control a water valve position with one of the PWM out on the MC43, but not getting the expected results. 

The datasheet specifies a leakage current of 2mA. What do you recommend to clean this up and bring it down close to 0?

I am relatively new to the whole IQAN infrastructure and I am wondering why is there such a high leakage current? Is there any benefit to it?

Thanks in advance

Answered

The PWM out HS on the MC4x is primarilly designed to control coils, rather than as a signal output to another device that takes a PWM command. If you run out of COUT:s, or need to control a coils at currents below the COUT control range this output type is a good choice. 

The relatively high leakage current on this output comes from an internal pull-up resistor that is used by the off-state open load detection. 


You might be able to overcome this by adding an external pull-down resistor (needs to be sufficiently low resistance to make sure the voltage drops below the low trig level for your input device when the output is off, while at the same time being able to handle the power dissipation when the output is on.