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Electronics => Electronics => Topic started by: ed1380 on April 27, 2007, 04:16:51 PM

Title: electronics question
Post by: ed1380 on April 27, 2007, 04:16:51 PM

I'm kinda starting to understand circuits and stuff, so this thread is to get rid of any doubts I ever get.

http://www.allegromicro.com/en/Products/Part_Numbers/2559/2559.pdf
what do you use K for?(pins 2 and 7)
my guess is just plain + or -


and put +5v to pin 14, with a .1uf cap.
no need to do the weird thing with pull up or down resistors?
or output high to that pin with mcu

Title: Re: electronics question
Post by: ed1380 on April 27, 2007, 04:22:37 PM

ohh and put diodes on outputs.
any need for caps on the imput?

Title: Re: electronics question
Post by: ed1380 on April 28, 2007, 03:12:57 PM

bumpity bump

Title: Re: electronics question
Post by: Hal9000 on April 28, 2007, 04:21:02 PM

Yeah, I couldn't find what K means either. The datasheet isn't very comprehensive.

Title: Re: electronics question
Post by: Admin on April 28, 2007, 07:20:33 PM

hmmmm I cant figure it out either. I searched the PDF but it says nothing about it.

Looking at the Functional Block Diagram for clues . . . it appears that K can be ignored without any effect. I think K is for a special external feature, such as measuring out voltage? :-\

Title: Re: electronics question
Post by: pwdixon on August 11, 2010, 08:14:50 AM

I know this is old but someone might read this post and want a real answer.

The K pin is to a protection diode that normally gets connected to the power rail of the load you are switching.  The function of the diode is to capture high voltage spikes caused by inductive loads as these would possibly destroy the output transistor or radiate electrical noise.  I would guess they chose the letter K as it's the (c/k)athode of the diode.

Title: Re: electronics question
Post by: waltr on August 11, 2010, 01:07:42 PM

Just saw this thread revived. The last post has the answer. The pins labeled K allows use of the diode to protect the device against inductive loads. Tie those pins to the top side of the inductive load.

Title: Re: electronics question
Post by: madsci1016 on August 11, 2010, 01:48:12 PM

Just to clarify, the chip has a built in diode for inductive loads. If it didn't have one, you would add one to your circuit. But since it has one, you just tie K to the high side of your inductive load and then you are protected.

You can drive relays using these with no more parts needed.