8.2.1.2 Detailed Design Procedure

The passive components shown in Figure 53 are selected using the information given in the Application Information and Layout Guidelines sections. All 10-µF input ac-coupling capacitors (C1, C2, C3, and C4) maximize the CMRR performance at low frequency, as shown in Figure 50. The high-pass corner frequency for input signals meets the design requirement for frequency response, as Equation 6 shows:

Equation 6.

The 1-MΩ R_COM resistors (R3 and R4) further improve CMRR performance at low frequency. Resistors R1, R2, R4, and R5 provide a discharge pathway for the ac-coupling capacitors in the event that audio equipment with a dc offset voltage is connected to the inputs of the circuit. These resistors are optional and may degrade the CMRR performance with mismatches in source impedance. Finally, capacitors C5, C6, C7, and C8 provide a low-impedance pathway for power supply noise to pass to ground rather than interfering with the audio signal. No connection is necessary on the VMID(IN) and VMID(OUT) pins because the supply-divider circuit is not used in this particular application.