Loudness Function External Circuit Constant Calculation Example

First, refer to the LC75366 and LC75366M 10 dB step internal equivalent circuit shown on page 5. Figure 1 below

shows this circuit simplified with the external components used for the loudness function connected for this calculation.

The sample calculation below uses this diagram to acquire a 5 dB boost at f = 100 Hz.

(f = 100 Hz, 5 dB boost)

Let R and C in Figure 1 be:

R1 = R2 = 10 k

Ω

R3 = 1 k

Ω

C1 = Z1, C2 = Z2

Then:

Solving the above equations gives:

Z1

≠ 178.3 kΩ and Z2 = 176 Ω

No. 4929-10/11

LC75366, 75366M

(at = 1 kHz)

+

R2 (R3 + Z2)

R2 + R3 + Z2

= –20 dB

R1 · Z1

R1 + Z1

R2 (R3 + Z2)

R2 + R3 + Z2

(at = 100 Hz)

+

= –15 dB

R1 · 10 · Z1

R1 + 10 · Z1

R2 (R3 + 10 · Z2)

R2 + R3 + 10 · Z2

R2 (R3 + 10 · Z2)

R2 + R3 + 10 · Z2