ADSP-BF523C Datasheet, PDF (14/44 Pages) Analog Devices – Blackfin Embedded Processor 289-ball MBGA package

ADSP-BF523C/ADSP-BF525C/ADSP-BF527C
Sidetone Mode
The sidetone mode routs the microphone input to the line and
headphone outputs as shown in Figure 17.
Preliminary Technical Data
10 K:
MICIN
50 K:
-
VMID
+
10DB GAIN BOOST
VMID
-
+
FROM
LINE
INPUTS
FROM
DAC
SIDETONE (ON)
BYPASS (OFF)
DACSEL (OFF)
-
VMID
+
LINEOUT
-
VMID +
HPOUT
Figure 17. Sidetone Mode
The sidetone mode allows the microphone input to be attenu-
ated to the outputs for telephone and headset applications.
The sidetone mode and attenuation are selected under software
control using the SIDETONE bit as shown in Table 9. In true
sidetone the output from the DAC (DACSEL) and line inputs
(BYPASS) should be deselected from the line output block.
However, this can also be used to sum the DAC output, line
inputs and microphone inputs together. The microphone boost
gain control and headphone output volume control and mutes
are still operational in sidetone mode. To avoid distortion the
maximum signal at any point in the sidetone path must be no
greater than 1.0 V(rms) at AVDD = 3.3V. This level tracks
directly with AVDD.
Table 9. Sidetone Mode Control
Register Bit Label
Address
Default Description
000 0100 5 SIDETONE 0
Sidetone Switch (analog)
1 = Enable Side Tone
0 = Disable Side Tone
7:6 SIDEATT[1:0] 00
Sidetone Attenuation
11 = –15 dB
10 = –12 dB
01 = –9 dB
00 = –6 dB
Rev. PrC | Page 14 of 44 | June 2008