4

DS1165F1

CS7331P

2 Typical Connection Diagram

2 Typical Connection Diagram

Figure 2-1. Typical Connection Diagram

The recommended connection of a CS7331P silicon microphone is shown in Fig. 2-1.

A DC-blocking capacitor is required on the OUTPUT pin. The capacitor must be correctly selected as it affects the cut-off

frequency of the output path. A low cut-off frequency is desirable to ensure there is no significant filtering of the audio

bandwidth.

The 3-dB cut-off frequency of the output path can be calculated using Eq. 2-1, where C is the output capacitance and R

is the input resistance of the audio codec.

Equation 2-1. Low-Pass Filter Calculation

A typical recommended configuration uses a 1-

F DC-blocking capacitor and a 20-k codec input impedance, which

results in a 3-dB cut-off frequency of 10 Hz or less. Tantalum electrolytic capacitors are particularly suitable for the

DC-blocking components as they offer high stability in a small package size.

It is also recommended to place a 0.1-

F decoupling capacitor close to the VDD pin of the CS7331P.

3 Characteristics and Specifications

Table 3-1. Parameter Definitions

Parameter

Definition

Sensitivity

A measure of the microphone output response to the acoustic pressure of a 1-kHz, 94 dB SPL (1 Pa RMS)

sine wave.

Total harmonic distortion (THD)

The ratio of the RMS sum of the harmonic distortion products in the specified bandwidth (see note) relative

to the RMS amplitude of the fundamental (i.e., test frequency) output.

Signal-to-noise ratio (SNR)

A measure of the difference in level between the output response of a 1-kHz, 94 dB SPL sine wave and the

idle noise output.

Dynamic Range (DR)

The ratio of the 10% THD microphone output level (in response to a sine wave input) and the idle noise

output.

Note: Unless otherwise specified, all performance measurements are specified with a 20-kHz, low-pass brick-wall filter and, where noted, an

A-weighted filter. The low-pass filter removes out-of-band noise.

Table 3-2. Recommended Operating Conditions

Parameter

Symbol

Min

Typ

Max

Units

Analog supply range

VDD

1.6

1.8

3.6

V

Ground

GND

—

0

—

V

Operating temperature range

–40

—

+85

ºC

Audio Codec

OUTPUT

VDD

GND

1

F

C

INPUT

1.8 V

0.1

F

CS7331P

3-dB filter cut-off frequency

1

2

RC

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