SGLS007G February 2003 – August 2022 TLC2272-Q1 , TLC2272A-Q1 , TLC2274-Q1 , TLC2274A-Q1
PRODUCTION DATA
Equation 1 and Equation 2 are used to calculate VOUT.
In an ideal case, Equation 3 then calculates R1 = R and R2 = Rg, and VOUT:
However, the resistors have tolerances; therefore, the resistors cannot be perfectly matched.
R1 = R ± ΔR1
R2 = R2 ± ΔR2
R = R ± ΔR
Rg = Rg ± ΔRg
Equation 5 shows that by developing the equations and neglecting the second order, the worst case is when the tolerances add up:
where
If the resistors are perfectly matched, then Tol = 0 and Equation 6 calculates VOUT:
The highest error is from the common mode:
Gain of 10, Rg / R = 10, and Tol = 1%:
Common mode error = ((4 × 0.01) / 1.1) × 12 V = 0.436 V
Gain of 10 and Tol = 0.1%:
Common mode error = 43.6 mV
The resistors were chosen from 2% batches.
R1 and R 12 kΩ
R2 and Rg 120 kΩ
Ideal Gain = 120 / 12 = 10
The measured value of the resistors:
R1 = 11.835 kΩ
R = 11.85 kΩ
R2 = 117.92 kΩ
Rg = 118.07 kΩ