PWM drive IC operating on around 36V - Page 1
Forum section: electronics / projects

author: Simon
author_rank: Unknown
timestamp: November 20, 2012, 01:09:03 pm
content: I'm trying to replace an archaic 555 PWM circuit with a PWM IC that will run on 36V (or more or very slightly less), it can be anything DIP or SOIC, Ideally I will supply this with 24V vehicle supply, and have a pot input to it to provide PWM output, RS and Farnell have turned up nothing, It needs to be a -40/+125C ideally, at least 105C

author: mazurov
author_rank: Frequent Contributor
timestamp: November 20, 2012, 07:02:08 pm
content: Any DC-DC converter IC is a PWM drive IC. Potential on a feedback pin sets the duty cycle.

author: Fluxed Matter
author_rank: Regular Contributor
timestamp: November 20, 2012, 07:09:49 pm
content: Hi Simon. Trying looking up UC3844. I believe it is up to 30V so I not sure if that meet your criteria.

author: mrflibble
author_rank: Super Contributor
timestamp: November 21, 2012, 12:10:46 am
content: The UC3844 is indeed nice, but (just did doublecheck) it's max 30 V like you mention. So I guess suitability depends on Simon's definition of "very slightly".

author: Psi
author_rank: Super Contributor
timestamp: November 21, 2012, 12:21:04 am
content: The good old TL494 will run from 40V.Sadly it's only -40C -> 85C thoughThe TL494 was used in many car amps so it has been used for automotive stuff in the past, however if you plan to have your device mounted in the engine bay then i agree that you want at-least 105C

author: xygor
author_rank: Regular Contributor
timestamp: November 21, 2012, 12:56:13 am
content: Linear Tech has several. LTC3810 for example.

author: poorchava
author_rank: Super Contributor
timestamp: November 21, 2012, 09:00:30 am
content: QuoteBut car amp is not exactly a "hard" automotive spec. Of course it has to withstand voltage pulses, load dumps etc but it's typically mounted inside passenger compartment so temperature rating doesn't have to be very high. I think 85*C will perfectly do - of course unless customer specifies otherwise.What's the exact application? I mean does that only have to generate PWM, or serve as SMPS driver or Motor driver or what? I would look at Infineon's offer. They have very wide portfolio of automotive stuff, which often operates up to 45V or even 60V.

author: Simon
author_rank: Unknown
timestamp: November 21, 2012, 10:16:09 am
content: THANK YOU FOR ALL OF YOUR SUGESTIONS, I have managed to get hold of the datasheet of the motor being controlled and it will take anything over 12V as a high so potentially anything powered at 15+V will also do it. I was also looking for something fairly cheap. Although now I know I can knock out the "output" stage on the existing circuit if i change the supply voltage to 15V rather than the 12V it has now

author: blackdog
author_rank: Frequent Contributor
timestamp: November 21, 2012, 10:33:03 am
content: Hi Simon,Look @ SG3525a, its 0,73 Euro on the Farnell website.40V max0.5A output current.http://www.st.com/internet/analog/product/75183.jspKind regarts,Bram

author: Simon
author_rank: Unknown
timestamp: November 21, 2012, 12:26:10 pm
content: thanks, but maximum duty of 45% ? hm sadly this only goes to 85C, I think I may be stuck with the 555

author: blackdog
author_rank: Frequent Contributor
timestamp: November 21, 2012, 12:42:35 pm
content: Hi SimonI use it to control a Van on a PWM freq of 15KHz, and it wil go to about 95% and after that, it Will jump to 100%.Maybe you can test a few parts to see if on the freq you using it it Will go high enough...Kind regarts,Blackdog

author: jeroen74
author_rank: Frequent Contributor
timestamp: November 21, 2012, 01:03:03 pm
content: The SG3524 is meant to be used with a push pull stage, hence the 45%. You can double that I guess by combining the outputs.

author: Simon
author_rank: Unknown
timestamp: November 21, 2012, 01:12:45 pm
content: I am afraid that the datasheet does not say much at all.

author: jeroen74
author_rank: Frequent Contributor
timestamp: November 21, 2012, 01:20:40 pm
content: What is the exact purpose of the circuit? Maybe you can just use the classic two transistor multivibrator circuit.

author: Zero999
author_rank: Super Contributor
timestamp: November 21, 2012, 02:06:58 pm
content: You could use a comparator IC such as the LM339 or LM393 to do PWM. It needs more external components though.

author: Simon
author_rank: Unknown
timestamp: November 21, 2012, 03:03:25 pm
content: PWM DRIVE OF A MOTOR, CAN i GET VARIAble duty ?

author: blackdog
author_rank: Frequent Contributor
timestamp: November 21, 2012, 03:46:28 pm
content: Hi Simon,This is as simple as i gets...The bottem part is for youand the top part is my Van controler for my Dynamic Load.If the wiper of P1 is connected to R1 the pwm is offIf the wiper is connected to R2 the pwm is on.Control is from 0 to 100%R60 and C32 is stting the frequentie, here about 15khz.Use a Fet to control your motor...EditPotmeter from 10 to 1K, litle brain fart ;-)Kind regarts,Blackdog

author: SeanB
author_rank: Super Contributor
timestamp: November 21, 2012, 04:17:23 pm
content: To get more than 50% duty cycle join pins 13 and 12. Still limited current wise as you then have each output device switching alternately. You will not get 100% but will get up to the deadtime X2 from it