WM7331E Datasheet, PDF (7/12 Pages) Cirrus Logic – Bottom Port Analog Silicon Microphone

WM7331E
APPLICATIONS INFORMATION
RECOMMENDED EXTERNAL COMPONENTS
WM7331 ^VDD
GND
OUTPUT
C
1F
-
+
R
Figure 1 WM7331 Recommended External Components
A DC-blocking output capacitor is required on the OUTPUT pin, as illustrated in Figure 1. A single
capacitor is required for a single-ended connection. The capacitor must be correctly selected as it
affects the cut-off frequency of the output path. A low cut-off frequency is desirable as it means there
is no significant filtering of the audio bandwidth.
The 3dB cut-off frequency of the output path is given by the equation below, where C is the output
capacitance and R is the input resistance of the other circuit.
3dB
filter
roll-off
frequency
=
1
2 ^p RC
A typical recommended configuration, with 1uF DC-blocking capacitor and 20kΩ minimum input circuit
impedance, gives a 3dB cut-off frequency of 10Hz or less. Tantalum electrolytic capacitors are
particularly suitable for the DC-blocking components as they offer high stability in a small package
size.
Rev 3.2
7