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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Output limited- SR controled Driver https://designers-guide.org/forum/YaBB.pl?num=1232463278 Message started by XY-oriented on Jan 20th, 2009, 6:54am |
Title: Output limited- SR controled Driver Post by XY-oriented on Jan 20th, 2009, 6:54am Hello, is there anybody who knows a structure of a high current capability drvier with: - Slew rate control - Output must be limited to Vref+ and Vref- (programmable voltage source basically) - the driver must source/sink current from/into the power supply and not Vref+/- I found some circuits ideas for the slew rate control but I couldnīt clip the output at the right Vref+/- "in an elegant way" any circuits ideas or papers links ? |
Title: Re: Output limited- SR controled Driver Post by thechopper on Jan 20th, 2009, 6:28pm Are you trying to drive a large capacitive load? In this case a simple SR control circuit would involve a current starving inverter, where such current is used for controlling the output SR. One option for limiting the voltage swing to VREF+/- would be to use active clampers; i.e. two comparators looking at the driver's output voltage and turning on a control signal when hitting VREF+/-. Such control signal could - for example - modulate a Resistance in series with your driver in such a way it keeps the voltage constant if it tries to go beyond VREF. Regards Tosei |
Title: Re: Output limited- SR controled Driver Post by XY-oriented on Jan 21st, 2009, 4:06am Thanks for your replay Tosei, Actually the current starving inverter is not an option for me because the SR must be controlled over a wide range of load capacitance. one idea is to generate a "wave form" with the proper SR followed by a SR-free buffer. my problem is how to limit the output to Vref+/- - If I use active clippers at the driver output I will burn a lot of current inside the chip. - Controlling the amplitude of the SR shaping waveform feeding the Buffer in a feedback loop require a huge bandwidth (the driver is supposed to work at 20MHz). I am designing a substitute chip, and the old one has such a smooth settling behavior that I am convinced that they didnīt use a feedback loop. It must be something else ! :-/ |
Title: Re: Output limited- SR controled Driver Post by thechopper on Jan 21st, 2009, 6:41pm XY-oriented wrote on Jan 21st, 2009, 4:06am:
Iīm not sure about this. If you used a simple comparator which might consume a little current and such comparator could linearly control a RON in series with the output driver once the output voltage hits your threshold that would make it without burning a lot of power. Regards Tosei |
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