Hi! I need help with part of an assignment. It is about a 12-bit AD Converter.
First with given Vref=3.3 V and digital output i were to calculate Vin at that time => Vin=780.879 mV. I also had to calculate the LSB=805.664*10^-6 V.
So now an analog multiplexer is connected, with inner resistance Ri=7000 ohm and generates 0-Vref V. It now looks like an RC circuit. Given values are the R in the RC circuit is R=3000 ohm and C=12 pF.
First task was to find the time of the capacitor (which is initially uncharged) to reach 1/4 LSB accuracy in the worst case scenario.
I found a formula which i used that stated: t=-ln(1/(2^N*4))*RC where i used R=R+Ri, given C and N=12.
Next task is the one i need help with! Now i should with same conditions as above calculate the time of the capacitor to reach 1/4LSB accuracy but only when using the 6 most significant bits of the result.
How do i do that? I tried the same formula but with N=6 but it gave apparently wrong answer. I also divided first calculated time in 2 because i thought it would help, but it didn't.
Maybe i need to use another formula or something, im clueless.
Thanks!
First with given Vref=3.3 V and digital output i were to calculate Vin at that time => Vin=780.879 mV. I also had to calculate the LSB=805.664*10^-6 V.
So now an analog multiplexer is connected, with inner resistance Ri=7000 ohm and generates 0-Vref V. It now looks like an RC circuit. Given values are the R in the RC circuit is R=3000 ohm and C=12 pF.
First task was to find the time of the capacitor (which is initially uncharged) to reach 1/4 LSB accuracy in the worst case scenario.
I found a formula which i used that stated: t=-ln(1/(2^N*4))*RC where i used R=R+Ri, given C and N=12.
Next task is the one i need help with! Now i should with same conditions as above calculate the time of the capacitor to reach 1/4LSB accuracy but only when using the 6 most significant bits of the result.
How do i do that? I tried the same formula but with N=6 but it gave apparently wrong answer. I also divided first calculated time in 2 because i thought it would help, but it didn't.
Maybe i need to use another formula or something, im clueless.
Thanks!
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