PWM IC voltage controlled

[Winsu]

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_luis]

. 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]

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]

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]

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.

Regards, Dana.

 

[danadakk]

Another more precise approach is to use PSOC.

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.

https://www.cypress.com/documentation/development-kitsboards/cy8ckit-059-psoc-5lp-prototyping-kit-onboard-programmer-and

Regards, Dana.

 

[KlausST]

Hi,

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

Klaus

 

[Winsu]

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]

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?.

 

[betwixt]

??
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]

??
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...?.