Sawtooth Voltage Generator

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Hi guys, I am trying to think about a sawtooth votlage generator and I concluded that I will need a comparator, current source (through current mirror) and a capacitor). However, I can't find any circuit which can do this.

Does anyone knows any good reference for this?

Kind regards.
 

Many different solutions exist depending your requirements.

Pls state them first, always.

frequency range KHz, MHz mHz?
Max slew rate of step to origin V/us
Amount of overshoot tolerated%
Output voltage range?
source Impedance ?
Expected load impedance R,C,L?
Linearity error on ramp? %

 

Hi and thanks for the reply.

The sawtooth generator is to be used inside an IC as part of a system.

It's to be operated >300MHz, output voltage range from 0V up to 3.3V and it's output is to be connected into a comparator (this sawtooth waveform is to be compared to a reference). Hope this info is enough because the other questions I don't have a clue of the requirements. I wonder if for the application is important.

Regards.
 


They are very important. A Sawtooth has two ramps. 3.3V at 300MHz or 3.3ns is 1000V/us. Thus the end of the sawtooth ought to be 100x faster ramp,, depending on application. 100,000V/us is not practical.

100kV/us with 1 pF load.
Let's see
Ic=1pF 0.1V/ps= 100mA with a switching time of 3.3ns/100= 33ps




Pls try again.. Why sawtooth and what are the slew rate requirements?
 
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    AMSA84

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TO be honest, everything is open and nothing is defined. Yet, I don't know what kind of requirements a sawtooth needs.

It is a sawtooth because it is for a buck/boost converter.

Regarding the slew rate requiremente, we could go other way around, the current consumption on this block should not be greater than 1mA.
 

I have seen one or two works where this was done (high frequency PWM generators) where the sawtooth was implemented. Who says sawtooth, says a triangular waveform.
 

Maybe the authors that I am talking about made a triangular instead of ramp.

Another thing that came up to my mind is that maybe the sawthooth doesn't need to come from 0 up to 3.3V but from a certain voltage level, accounting with the transients, up to some other voltage level. For example, from 1V up to 2.5V.

https://ieeexplore.ieee.org/xpl/art...hip+components+for+integrated+dc-dc+converter

https://ieeexplore.ieee.org/xpl/art...icient+dc-dc+down+converter+based+on+dual+die

https://ieeexplore.ieee.org/xpl/art...mber=4672009&queryText=fully-integrated+dc-dc

https://ieeexplore.ieee.org/xpl/art...mber=6264597&queryText=fully-integrated+dc-dc

https://ieeexplore.ieee.org/xpl/art...mber=5316434&queryText=fully-integrated+dc-dc

And thinking now on the triangular, how can that be done?
 

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