Supply voltage of my design is +1.8V. I have an on chip negative converter in my design which converts +1.8 to -1.8V(ideally).It generates a negative voltage of around -1.78 to -1.7V with ripple of 100mV peak to peak.I need to decrease that ripple on the negative voltage converter.So, I need a block which regulates that ripple from 100mV to 12mV.That block should be on chip.Is it possible to do that?
I assume the chip is GaAs MESFET technology? What's the Vth? How precise are the resistors? Do they let you use a Schottky diode as a standalone circuit element?
It is 180 nm cmos technology.vthp is -0.455V and vthn is 0.307V.As long it is on chip ,we can use any component.
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Yes it is possible. Reducing the ripple will increase the silicon area and increase the power consumption. It may also reduce the magnitude of the negative voltage.
A very expensive way to accomplish this is: use a charge pump voltage doubler to convert your -1.7 volt supply, into a -3.4 volt supply (with even more ripple). Then build a series pass voltage regulator (CMOS equivalent of the LM7805) which takes -3.4 volts in and produces -1.8 volts out, with very low ripple. You may need to use thicker gate oxide transistors (designed for I/O uses) to withstand the -3.4 volt oxide stress.
But that's just a thought experiment, an "existence proof" which demonstrates that it is possible, at least in theory. In practice you will want to consult with other experienced designers to engineer a low cost solution. Ideally, long before your design review.
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