Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

PWM IC voltage controlled

Winsu

Full Member level 2
Joined
Oct 25, 2017
Messages
135
Helped
1
Reputation
2
Reaction score
1
Trophy points
18
Activity points
1,285
Hi All,

I need to get a PWM output signal of 5V amplitude controlled by voltage ( 0V to 1V). I came across with this IC LTC 6992. My problem is that it cannot be sourced from Farnell, then I tried to look for an alternative in Farnell and I couldn't. Then I looked for more ICs that could do the same thing and I haven't found many , actually I haven't found any one that mimics the LTC 6992. By mimics I mean similar Vin, similar voltage control...etc. Is there any reason why there are not many in the market?, I was expecting that this type of IC was going to be very common.

Thanks,
Winsu.
 

andre_teprom

Super Moderator
Staff member
Joined
Nov 7, 2006
Messages
9,163
Helped
1,140
Reputation
2,298
Reaction score
1,113
Trophy points
1,403
Location
Brazil
Activity points
53,185
. Is there any reason why there are not many in the market?
People would prefer an off-the-shelf option such as by using the 555, perhaps not meeting all advantages (if there) of a dedicated IC, but at least easy to find anywhere; I surelly have some in my lab.
 

d123

Advanced Member level 5
Joined
Jun 7, 2015
Messages
1,987
Helped
445
Reputation
891
Reaction score
436
Trophy points
83
Activity points
20,304
Hi,

Digikey appear to have that IC in stock. What about sourcing direct from manufacturer (if it's not just a one-off design)?
 

schmitt trigger

Advanced Member level 5
Joined
Apr 17, 2013
Messages
2,649
Helped
844
Reputation
1,692
Reaction score
819
Trophy points
1,393
Activity points
17,772
I will suggest what other people are already thinking: would you consider a small microcontroller?

Reading the analog control voltage and outputing a variable PWM, is a task which should require only a few lines of code and even the smallest micro should be capable of doing.
 

danadakk

Full Member level 4
Joined
Mar 26, 2018
Messages
216
Helped
31
Reputation
61
Reaction score
30
Trophy points
28
Activity points
1,107
One approach

Use mBlock with an Arduino board, say Nano, or with ATTINY85. Mblock takes user
blocks, you drag them onto design canvas, config them, then mBlock converts that
to Arduino code and you program part. You can see the mBlock window, 3'rd from left,
pretty simple to create this application. You application would have to add a couple
of math blocks to scale it for the 1V solution you want.

V to PWM mBlock.PNG

V to PWM.PNG


Regards, Dana.
 

danadakk

Full Member level 4
Joined
Mar 26, 2018
Messages
216
Helped
31
Reputation
61
Reaction score
30
Trophy points
28
Activity points
1,107
Another more precise approach is to use PSOC.

VtoPWM PSOC.PNG

This takes a small amount of code, say ~ 10 lines.

It is much more precise, A/D and PWM both 16 bits. A/D much more accurate with onboard .1% Vref,
same for PWM timing, clock accuracy w board below << .1%.

Right had window shows other chip resources (this is all one chip), like DAC, Mixer, OpAmps, comparators,
lots of logic like simple gates to LUTs for simple state machines, DSP, see attach catalog of whats on the
chip.

Board is $ 10, family is PSOC 5LP. IDE and compiler free, PSOC Creator.



Regards, Dana.
 

Attachments


KlausST

Super Moderator
Staff member
Joined
Apr 17, 2014
Messages
17,465
Helped
3,945
Reputation
7,888
Reaction score
3,815
Trophy points
113
Activity points
115,787
Hi,

A dual comparator could also do the job.
One for the triange generation, the other for the PWM generation.

Klaus
 

Winsu

Full Member level 2
Joined
Oct 25, 2017
Messages
135
Helped
1
Reputation
2
Reaction score
1
Trophy points
18
Activity points
1,285
Hi,

Digikey appear to have that IC in stock. What about sourcing direct from manufacturer (if it's not just a one-off design)?
Thanks, I know it is available in other supplier, I don't wont to order for just one component to save shipping fees, thanks
 

Winsu

Full Member level 2
Joined
Oct 25, 2017
Messages
135
Helped
1
Reputation
2
Reaction score
1
Trophy points
18
Activity points
1,285
Hi,

A dual comparator could also do the job.
One for the triange generation, the other for the PWM generation.

Klaus

I was actually working on that I have simulated the sawtooth wave, I need a comparator to get the PWM signal running. Not sure how you would do it with just two op amps. On that way I think I would need three op amps. One for the astable multivibrator, another one for the sawtooth and the last one for the comparator?.


1592428428881.png

1592428508549.png
 

betwixt

Super Moderator
Staff member
Joined
Jul 4, 2009
Messages
14,190
Helped
4,685
Reputation
9,385
Reaction score
4,439
Trophy points
1,393
Location
Aberdyfi, West Wales, UK
Activity points
121,177
??
Use the signal across C1 as one comparator input and the control voltage as the other. You don't have to start with a square wave then make it into a triangle wave.

Brian.
 

Winsu

Full Member level 2
Joined
Oct 25, 2017
Messages
135
Helped
1
Reputation
2
Reaction score
1
Trophy points
18
Activity points
1,285
??
Use the signal across C1 as one comparator input and the control voltage as the other. You don't have to start with a square wave then make it into a triangle wave.

Brian.
Indeed Brian, I could use the charge and discharge trace from the capacitor but, would it have an effect in the quality of the PWM signal as it is a bit curvy...?.
 

Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top