Opto-Coupler

1. AC Interface

Using HCPL-3700 from Agilent Technology.

For the mode of Input Clamp Voltage, we have

Vihc2 = 6.7 v

|Iin| = 10 mA

we have

Vr = Vpk - Vihc2 = 240*1.414 - 6.7 = 332.7 v

So

Rx = Vr / |Iin| = 332.7 / 10 = 33.3 K

R_x/2 = 16.7 K

Use R_x/2 = 18.7 K, 1%, so

P_x/2 = (Vr/2)² / R_x/2 = 1.5w

Choose

R_x/2 = 18.7 K,1%, 1.5 w

2. Isolation Amplifier

Using HCNR-0201 from Agilent Technology.

Data sheet gives I_F = 1 ~ 20 mA, choose I_F = 2 mA, we have

R₃ = (V_CC - V_F)/I_F = 5/2 = 2.5 K

Data sheet gives

I_PD1 = K₁ * I_F = 0.5 * 2 = 1 mA

so

R₁ = V_IN / I_PD1 = 5/1 = 5 K

as V_IN is an analog signal out of a 5-v DAC (Digital Analog Converter)

Data sheet gives

I_PD2 = K₃ * I_PD1 = 1 * 1 = 1 mA

so

R₂ = V_CC / I_PD2 = 5/1 = 5 K

C₁ is for C₁R₁ to meet F_max

C₂ is for C₂R₂ to meet F_max