CS47L35 datasheet(229/300 Pages) CIRRUS

229 / 300 page

DS1085F3

229

CS47L35

5.1 Recommended External Components

The external connections for digital microphones, incorporating the CS47L35 microphone bias circuit, are shown in

Fig. 5-4. Ceramic decoupling capacitors for the digital microphones may be required—refer to the specific

recommendations for the application microphones.

If two microphones are connected to a single DMICDAT pin, the microphones must be configured to ensure that the Left

mic transmits a data bit when DMICCLK is high, and the Right mic transmits a data bit when DMICCLK is low. The

CS47L35 samples the DMIC data at the end of each DMICCLK phase. Each microphone must tristate its data output when

the other microphone is transmitting. Integrated pull-down resistors can be enabled on the DMICDAT pins if required.

The voltage reference for each DMIC interface is selectable. It is important that the selected reference for the CS47L35

interface is compatible with the applicable configuration of the external microphone.

5.1.3

Microphone Bias Circuit

The CS47L35 is designed to interface easily with analog or digital microphones.

Each microphone requires a bias current (electret condenser microphones) or voltage supply (silicon microphones); these

can be provided by the MICBIAS regulators on the CS47L35. Two MICBIAS generators are available; switchable outputs

allow four separate reference/supply outputs to be independently controlled.

Note that the MICVDD pin can also be used (instead of MICBIASnx) as a reference or power supply for external

microphones. The MICBIAS outputs are recommended, as these offer better noise performance and independent enable/

disable control.

Analog microphones may be connected in single-ended or differential configurations, as shown in Fig. 5-2. The differential

configuration provides better performance due to its rejection of common-mode noise; the single-ended method provides

a reduction in external component count.

A bias resistor is required when using an ECM. The bias resistor should be chosen according to the minimum operating

impedance of the microphone and MICBIAS voltage so that the maximum bias current of the CS47L35 is not exceeded.

A 2.2-k

 bias resistor is recommended; this provides compatibility with a wide range of microphone components.

Figure 5-2. Single-Ended and Differential ECM Microphone Connections

Analog MEMS microphones can be connected to the CS47L35 as shown in Fig. 5-3. In this configuration, the MICBIAS

generators provide a low-noise supply for the microphones; a bias resistor is not required.

To ADC

VREF

IN1xN,

IN2xN

IN1xP,

IN2xP

ECM

GND

MICBIAS

PGA

–

To ADC

VREF

IN1xN,

IN2xN

IN1xP,

IN2xP

ECM

GND

MICBIAS

PGA

–

CS47L35 Datasheet(PDF) 229 Page - Cirrus Logic

CS47L35 Datasheet(HTML) 229 Page - Cirrus Logic

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL