3 1) Swap U1 Vin/Vout -- 3 cuts + 3 wires
7 1) U1 Vin/Vout pins are swapped
10 Use a SNLVC2G06 (dual open collector inverter):
19 Assuming that the capacitor is clamped to VOL most
20 of the time, the R*C that corresponds to charging
21 from VOL to VIH in T seconds:
23 The basic capacitor charging equation:
25 V(t) = VOL + (VCC - VOL) * (1 - e(-t/R*C)) (1)
27 Replacing V(t) with VIH and T:
29 VIH = VOL + (VCC - VOL) * (1 - e(-T/R*C)) (2)
33 (VIH - VOL)/(VCC - VOL) = 1 - e(-T/R*C)) (3)
35 e(-T/R*C) = 1 - (VIH - VOL)/(VCC - VOL) (4)
37 -T/R*C = ln(1 - (VIH - VOL)/(VCC - VOL)) (5)
39 R*C = -T/ln(1 - (VIH - VOL)/(VCC - VOL)) (6)
41 Substituting in for T=1ms, VIH, VOL, and VCC:
43 R*C = -.001/ln(1 - (3.5 - .55)/(5 - .55)) (7)
51 R = .009196 / .0000001 = 9196
53 Using an R near 10K should do the trick:
55 The maximum discharge current is IOL. Use Ohm's law
56 to determine determine discharge resistor:
63 Setting Rdischarge = 180 should be good enough.
65 The charge/discharge ratio is:
67 Rcharge/Rdischarge = 10K/180 = 55.5