Question

How do I solve Q4 of H8P3 - Memory "Time to Charge Capacitance Q2 to VOH"?
I tried using the first order dynamics equation:
VOH = VG2max + (VOL-VG2max) * exp(-t/TAU)
with TAU = R*CGS
and R = RON + RPU || ROFF
but I get t = 122.669 ps which seems to be wrong.

Answer 1

I did the same and get the same result....

Answer 2

at least no error in my numbers but rather in my formula. I'll take a depper look again by tomorrow.

Answer 3

if i find de solution e post

Answer 4

VS=5.0V, VOH=3.5V, VIH=3.0V, VIL=0.9V, VOL=0.5V

The gate-source capacitance CGS=3.5fF and VT=1.0V.

RON=1900.0Ω, ROFF=105.0MΩ and RPU=12.0kΩ.


can you tell me why this is wrong?

(3.5-4)/(0.5-4) = exp(-t/τ)

exp(-t/τ) = 0.142857142857

-t/τ = ln(0.142857142857) = -1.94591014906

t = T * 1.94591014906

R = 1900 + ((12000 * 105000000)/(12000 + 105000000)) = 13898.6287281 = 13.8986287281 kΩ

T = RC = 13898.6287281 * 3.5E-15 = 4.86452005484e-11

t = 4.86452005484e-11 * 1.94591014906 = 9.46591894502e-11 = 94.6591894502 ps

Answer 5

that is the same calculation as above, just different values. Still, I don't know whats wrong with it.

Answer 6

I did the same reasoning but with different values ​​and also not getting the correct answer