CS47L35 datasheet(31/300 Pages) CIRRUS

31 / 300 page

DS1085F3

CS47L35

4.2 Input Signal Path

For single-ended input, the microphone signal is connected to the noninverting input of the PGAs (INnLP or INnRP). The

inverting inputs of the PGAs are connected to an internal reference in this configuration.

For differential input, the noninverted microphone signal is connected to the noninverting input of the PGAs (INnLP or

INnRP), while the inverted (or noisy ground) signal is connected to the inverting input pins (INnLN or INnRN).

Note: Pseudodifferential connection is also possible—this is similar to the configuration shown in Fig. 4-4, but the GND

connection is directly to the microphone (and INnxN capacitor), instead of via a resistor. This is the recommended

configuration if the external accessory detection functions on the CS47L35 are used. The INnx_SRC field settings

are the same for pseudodifferential connection as for differential.

The gain of the input PGAs is controlled via register settings, as defined in Section 4.2.6. Note that the input impedance

of the analog input paths is fixed across all PGA gain settings.

The ECM analog input configurations are shown in Fig. 4-3 and Fig. 4-4. The integrated MICBIAS generators provide a

low noise reference for biasing the ECMs.

Analog MEMS microphones can be connected to the CS47L35 in a similar manner to the ECM configurations. Typical

configurations are shown in Fig. 4-5 and Fig. 4-6. In this configuration, the integrated MICBIAS generators provide a

low-noise power supply for the microphones.

Note: The MICVDD pin can also be used (instead of MICBIAS) as a reference or power supply for external microphones.

The MICBIAS outputs are recommended, because they offer better noise performance and independent enable/

disable control.

4.2.2

Analog Line Input

Line inputs can be connected to the CS47L35 in a similar manner to the mic inputs. Single-ended and differential modes

are supported on each analog input path. The mode is selected using INnx_SRC, as described in Section 4.2.6.

Figure 4-3. Single-Ended ECM Input

Figure 4-4. Differential ECM Input

Figure 4-5. Single-Ended MEMS Input

Figure 4-6. Differential MEMS Input

To ADC

VREF

IN1xN,

IN2xN

IN1xP,

IN2xP

ECM

GND

MICBIAS

PGA

–

To ADC

VREF

IN1xN,

IN2xN

IN1xP,

IN2xP

ECM

GND

MICBIAS

PGA

–

To ADC

VREF

IN1xN,

IN2xN

IN1xP,

IN2xP

MEMS

Mic

MICBIAS

VDD

OUT

GND

PGA

–

MEMS

Mic

To ADC

VREF

IN1xN,

IN2xN

IN1xP,

IN2xP

MICBIAS

VDD

OUT-P

GND

OUT-N

PGA

–

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