Relay drive using ULN2003. Microcontroller used is MSP430

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saurav_sdpl

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I also have the similar application of driving a latching relay with 500mA of current can i use ULN channels in parallel.

Also my input drive is from MSP430 controller.which has maximum capability of 5uA per pin.

Is it possible to interface
 

Are you sure about the 5uA specification because I think it is a few mA, which model are you using?

You can parallel the channels but note that the current is not 500mA for each channel, it is highly dependent of the duty ratio.



An alternative for 1.5A is ULN2065, ULN2069


Alex
 

Ya i am sorry, it is indeed 3mA in full drive strength mode.

I have a doubt, generally input of ULN is driven by a 5V and above voltage to keeping the transistor in saturation.

But i am operating MSP430 with 3V supply and want to operate latching relay whose coil current is 500mA.

In my design i am paralleling the ULN o/p for reliable operation.

Can i drive the input directly from microcontroller pin so that maximum collector current through each transistor is 300mA.

Because the datasheet doesnt not give any data from input current v/s input voltage .

Also i am confused whether i shld go for ULN or discreter transistor logic for a cheaper solution for driving the coil
 

Since you have a latching relay I suppose that you will just need a short pulse in the output so you can probably get 500mA even from one output but use two to be sure.
The input current is about 1mA @3.85v , also there is a specification for input voltage 3v to get Vce=2v @300mA output.

The alternative of using a small mosfet is not a bad idea, especially since you only want one output.

Alex
 

Or some logic gate from LVC or similiar family which are meant for level translation.
 

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