ADAU1781 Analog Devices, ADAU1781 Datasheet - Page 30

• Manufacturer Part Number: ADAU1781
• Description: SigmaDSP Low-noise Stereo Audio Codec for Portable Applications
• Manufacturer: Analog Devices

Specifications of ADAU1781

• Instructions/cycles: 1024
• Digital I/o Channels: 8/8
• Analog I/o Channels: 2/2
• Product Description: SigmaDSP low-noise stereo audio codec for portable applications

ADAU1781
RECORD SIGNAL PATH
INPUT SIGNAL PATH
The ADAU1781 can be configured for three types of microphone
inputs: single-ended, differential, or digital. The LMIC/LMICN/
MICD1 and RMIC/RMICN/MICD2 pins encompass all of these
configurations. LMICP and RMICP are used only during differen-
tial configurations (see Figure 30, the record signal path diagram).
Each analog input has individual gain controls (boost or cut). These
signals are routed to their respective right or left channel ADC.
Analog Microphone Inputs
For differential inputs, RMICN and RMICP denote the negative
and positive input for the right channel, respectively. LMICN
and LMICP denote the negative and positive input for the left
channel, respectively.
LMIC and RMIC inputs are single-ended line inputs. Together,
they can be used as a stereo single-ended input.
Digital Microphone Inputs
When a digital PDM microphone connected to the MICD1 or
MICD2 pin is used, Register 16392 (0x4008), digital microphone
and analog beep control, must be set appropriately to enable the
microphone input of choice. The MCKO output clock provides
the clock for the microphone and must be set accordingly in
Register 16384 (0x4000), clock control, depending on the
streaming PDM rate of the microphone.
The digital microphone signal bypasses the ADCs and is routed
directly into the decimation filters. The digital microphone and
ADCs share these decimation filters; therefore, both cannot be
used simultaneously.
Analog Beep Input
The BEEP pin is used for mono single-ended signals, such as a
beep warning. This signal bypasses the ADCs and the SigmaDSP
core and is mixed directly into any of the analog outputs.
RMIC/RMICN/
LMIC/LMICN/
RMICP
MICD1
LMICP
MICD2
BEEP
Figure 30. Record Signal Path Diagram
CM
CM
PGA
PGA
PGA
RIGHT
LEFT
ADC
ADC
DECIMATORS
Rev. B | Page 30 of 92
A BEEP pin input can also be amplified or muted by a PGA, up
to 32 dB in Register 16392 (0x4008), digital microphone and analog
beep control. The beep input must be enabled in Register 16400
(0x4010), microphone bias control and beep enable.
Microphone Bias
The MICBIAS pin provides a voltage reference for electret
microphones. Register 16400 (0x4010), microphone bias
control and beep enable, sets the operation mode of this pin.
Example Configurations
Figure 31. Stereo Digital Microphone Input Configuration
RMIC/RMICN/
RMIC/RMICN/
LMIC/LMICN/
LMIC/LMICN/
RMIC/RMICN/
LMIC/LMICN/
Figure 32. Single-Ended Input Configuration
Figure 33. Differential Input Configuration
RMICP
RMICP
MICD1
LMICP
MICD2
MICD1
LMICP
MICD2
RMICP
MICD1
LMICP
MICD2
CM
CM
CM
CM
CM
CM
TO DECIMATORS
TO DECIMATORS
PGA
PGA
PGA
PGA
PGA
PGA
TO LEFT
ADC
TO RIGHT
ADC
TO LEFT
ADC
TO RIGHT
ADC