CS47L85 datasheet(351/370 Pages) CIRRUS

351 / 370 page

CS47L85

Rev 4.3

351

Digital microphone connection to the CS47L85 is illustrated in Figure 90.

Ceramic decoupling capacitors for the digital microphones may be required - refer to the specific recommendations for the

application microphone(s).

Digital Mic

MICVDD or MICBIASn

AGND

Digital Mic

VDD

CLK

DATA

VDD

CLK

DATA

CHAN

VDD

DMICDATn

DMICCLKn

Digital

Microphone

Interface

The IN1, IN2, IN3 digital inputs are

referenced to MICVDD, or MICBIAS1/2/3.

The IN4, IN5, IN6 digital inputs are

referenced to DBVDD4.

The supply for each digital microphone

should the same voltage as the applicable

reference. Recommended that MICBIAS4

is used with IN4, IN5, IN6 only.

Figure 90 Digital Microphone Connection

The MICBIAS generators can each operate as a voltage regulator or in bypass mode.

See “Charge Pumps, Regulators and

Voltage Reference

” for details of the MICBIAS generators.

In Regulator mode, the MICBIAS regulators are designed to operate without external decoupling capacitors. The regulators

can be configured to support a capacitive load if required (e.g., for digital microphone supply decoupling). The compatible

load condition

s are detailed in the “Electrical Characteristics” section.

If the capacitive load on MICBIAS1, MICBIAS2 or MICBIAS3 exceeds the specified conditions for Regulator mode (e.g., due

to a decoupling capacitor or long PCB trace), then the respective generator must be configured in Bypass mode.

The maximum output current for each MICBIASn

pin is noted in the “Electrical Characteristics”. This limit must be observed

on each MICBIAS output, especially if more than one microphone is connected to a single MICBIAS pin. Note that the

maximum output current differs between Regulator mode and Bypass mode. The MICBIAS output voltage can be adjusted

using register control in Regulator mode.

HEADPHONE DRIVER OUTPUT PATH

The CS47L85 provides 3 stereo headphone output drivers. These outputs are all ground-referenced, allowing direct

connection to the external load(s). There is no requirement for DC blocking capacitors.

In single-ended (default) configuration, the headphone outputs comprise 6 independently controlled output channels, for up

to 3 stereo headphone or line outputs. In mono (BTL) mode, the headphone drivers support up to 3 differential outputs,

suitable for a mono earpiece or hearing coil load.

The headphone outputs incorporate a common mode, or ground loop, feedback path which provides rejection of system-

related ground noise. The feedback pins must be connected to ground for normal operation of the headphone outputs. A

separate feedback path is provided for each of the stereo headphone outputs. The HPOUT1 feedback is supported on two

pins - the applicable pin is selected using the ACCDET_SRC register bit.

The feedback pins should be connected to GND close to the respective headphone jack, as illustrated in Figure 91. In mono

(differential) mode, the feedback pin(s) should be connected to the ground plane that is physically closest to the earpiece

output PCB tracks.

It is recommended to ensure that the electrical characteristics of the PCB traces for each output pair are closely matched.

This is particularly important to matching the two traces of a differential (BTL) output.

Typical headphone and earpiece connections are illustrated in Figure 91.

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