What IC To Use To Convert TTL to 24VDC PNP Output - Page 1
Forum section: electronics / beginners

author: rantonides
author_rank: Contributor
timestamp: October 11, 2011, 05:10:26 am
content: Hi,Just new to circuit design. Really having trouble finding an IC to do a basic TTL to 24V Sourcing output. Someone told me to search for "High Side Switch", but I'm not really finding anything that seems right to me. When the TTL output is on (Pin goes to 0V), I want the output of the IC to be 24VDC. When the TTL output is off (5V), the output should be pulled down by a resistor. Maximum output around 500mA. Needs protection from switching solenoids and such.I know this should be dead common and simple, but I'm a noob.Thanks for any help. Cheers.

author: amspire
author_rank: Super Contributor
timestamp: October 11, 2011, 05:38:31 am
content: If you do a search for "High Side Driver". you should find a number of alternatives to wade through.Most of the modern devices will be mosfet output rather then PNP transistor, but that should be fine for you.Richard

author: Simon
author_rank: Unknown
timestamp: October 11, 2011, 06:01:52 am
content: you can probably do it with discrete transistors ? although if your looking to have a connection to ground and one to 24V for each state then you might want to look at something like a mosfet driver IC which may be able to source the current you want or you can use it to drive a pair of mosfets. Most of these chips take 5V logic signals and convert them

author: Jimmy
author_rank: Regular Contributor
timestamp: October 11, 2011, 11:23:54 am
content: If you are using cheep solenoids the you defiantly need to protect the micro. Does it need to be solid state and PNP?You can just use a relay with a 5v coil likehttp://search.digikey.com/us/en/products/TSC-105L3H,000/PB1017-ND/1095338

author: Zero999
author_rank: Super Contributor
timestamp: October 11, 2011, 04:32:40 pm
content: You don't need any ICs or a relay. Two BJTs will do, one PNP and one NPN.This circuit will work off 24V as well as 12V.http://www.winpicprog.co.uk/pic_tutorial_extras.htmT2 can be replaced with a P-channel MOSFET.

author: rantonides
author_rank: Contributor
timestamp: October 11, 2011, 06:00:56 pm
content: It would be nice for me to get an IC that has protection in it. When I search for "high side driver", I don't understand the following options...1. External Switch or Internal Switch?2. Configuration:- H Bridge- H Bridge, Half Bridge- Half Bridge- High and Low Side, Independent, Synchronous- High and Low Side, Synchronous- High SideAny thoughts?

author: Rufus
author_rank: Super Contributor
timestamp: October 11, 2011, 08:56:19 pm
content: Quote from: Hero999 on October 11, 2011, 04:32:40 pmAnd destroy itself the first time it sees a short circuit or inductive load.Infineon make some really nice smart high side switches like the ITS711 quad 4A 34v switch in an SO20 package, the main problem being Infineon has shit distribution so they are a pain in the ass to source.

author: Jimmy
author_rank: Regular Contributor
timestamp: October 11, 2011, 11:50:12 pm
content: You could wire it up as NPN and use a cheep ULN2003a Most of the controllers at work are NPNhttp://www.ti.com/lit/ds/symlink/uln2003a.pdfYou can pick them up for next to nothing eight channel ic for $0.40 that's 5c per 500ma channel. It is cheaper to make a NPN transistor than a PNP one.You just need to wire it up with a common 24v supply then sink the voltage to ground. Don't forget to use a protection diode for the solenoid's.If you need more current just parallel 2 channels together.

author: Zero999
author_rank: Super Contributor
timestamp: October 12, 2011, 04:51:38 pm
content: Quote from: Rufus on October 11, 2011, 08:56:19 pmIn which case you need you need to add a diode in reverse parallel with the load.