ADAU1761BCPZ-R7 datasheet(28/92 Pages) AD

28 / 92 page

Data Sheet

ADAU1761

RECORD SIGNAL PATH

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Rev. F | 28 of 92

Figure 33. Stereo Differential Microphone Configuration

The PGA can also be used for single-ended microphone inputs.

Connect LINP and/or RINP to the CM pin. In this configuration,

the signal connects to the inverting input of the PGA, LINN and/or

RINN, as shown in Figure 34.

Figure 34. Stereo Single-Ended Microphone Configuration

Analog Line Inputs

Line input signals can be accepted by any analog input. It is possi-

ble to route signals on the RINN, RINP, LINN, and LINP pins around

the differential amplifier to their own amplifier and to use these pins

as single-ended line inputs by disabling the LDEN and RDEN bits

(Bit 0 in Register R8, Address 0x400E, and Bit 0 in Register R9,

Address 0x400F). Figure 35 depicts a stereo single-ended line input

using the RINN and LINN pins.

The LAUX and RAUX pins are single-ended line inputs. They can

be used together as a stereo single-ended auxiliary input, as shown

in Figure 35. These inputs can bypass the input gain control,

mixers, and ADCs to directly connect to the output playback mixers

(see auxiliary bypass in Figure 32).

Figure 35. Stereo Single-Ended Line Input with Stereo Auxiliary Bypass

Digital Microphone Input

When using a digital microphone connected to the JACKDET/

MICIN pin, the JDFUNC[1:0] bits in Register R2 (Address 0x4008)

must be set to 10 to enable the microphone input and disable

the jack detection function. The ADAU1761 must operate in main

mode and source BCLK to the input clock of the digital microphone.

The DSPRUN bit must also be asserted in Register R62 (DSP run

The digital microphone signal bypasses record path mixers and

ADCs and is routed directly into the decimation filters. The digital

microphone and ADCs share decimation filters and, therefore, both

cannot be used simultaneously. The digital microphone input select

bit, INSEL, can be set in Register R19 (ADC control register,

Address 0x4019). Figure 36 depicts the digital microphone interface

and signal routing.

Figure 36. Digital Microphone Interface Block Diagram

Microphone Bias

The MICBIAS pin provides a voltage reference for electret analog

microphones. The MICBIAS voltage is set in Register R10 (record

microphone bias control register, Address 0x4010). In this register,

the MICBIAS output can be enabled or disabled. Additional options

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