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Texas Instruments How to Save Space and BOM Costs by Sharing Microphones Across Automotive Aubsyst Application notes
Application Report
SLAA915 – September 2019
How To Save Space And BOM Costs By Sharing
Microphones Across Automotive Subsystems
Krunal Maniar; Steve Wilson
ABSTRACT
As explained in the article “How to share eCall and Hands-Free Voice Command Recognition
Microphones across automotive subsystems to save system cost and space”, two dedicated microphones,
one for eCall and another one for hands-free voice application, are typically used in vehicles.
Texas Instruments’ automotive-grade audio codecs, TLV320AIC310x-Q1 (TLV320AIC3109-Q1,
TLV320AIC3104-Q1, and TLV320AIC3106-Q1) have two special modes called “Passive Direct Bypass”
and “Active PGA Bypass” that allow the use of one microphone for both eCall and hands-free application.
A microphone can be eliminated from the system altogether, resulting in significant cost and space
savings associated with the second microphone, cable routing, and microphone installation.
This application report explains the different ways one of the codecs, TLV320AIC3109-Q1, can be
configured in these special modes.
1
Contents
Configuring TLV320AIC3109-Q1 for Passive Direct Bypass or Active PGA Bypass Mode
.......................
2
List of Figures
1
Configuring TLV320AIC3109-Q1 for Bypass Path Options ............................................................ 2
List of Tables
Trademarks
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How To Save Space And BOM Costs By Sharing Microphones Across
Automotive Subsystems
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1
Configuring TLV320AIC3109-Q1 for Passive Direct Bypass or Active PGA Bypass Mode
1
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Configuring TLV320AIC3109-Q1 for Passive Direct Bypass or Active PGA Bypass Mode
BCLK
WCLK
DOUT
DIN
Figure 1 shows the functional block diagram of the TLV320AIC3109-Q1 (mono codec).
TLV320AIC3109-Q1
Audio Serial Bus Interface
Passive Direct
Bypass
(R37)
DIN
DOUT
HPCOM Volume
(0 to -78dB)
DAC_1
ADC_PGA
PGA_AUX
AGC
VCM
(R68)
(R67)
(R70)
+
HPCOM
(R72)
MIC1P / LINE1P
SW-D2
DAC_1
MIC1P / LINE1P
MIC1M / LINE1M
LINE1
+
(R19,
Gain:
0 to -12 dB R24)
1.5dB steps
PGA
ADC
Channel
Processing
HPF
SW-D1
Volume
Control
DAC
HPOUT Volume
(0 to -78dB)
DAC_3
DAC_1
ADC_PGA
PGA_AUX
(R15)
(R61)
(R60)
(R63)
+
HPOUT
(R65)
ADC_PGA
MIC1P / LINE1P
High Power
Output Stage Ctrl
(R40)
DAC_3
Passive Direct
Bypass
Active PGA
Bypass
DAC_1
ADC_PGA
PGA_AUX
SW-L1
SW-L0
LEFT_LOP
SW-L3
(R82)
(R81)
(R84)
LEFT_LOM
+
LINE1M
(R86) SW-L4
PGA_AUX
MIC2P / LINE2P
MIC2P / LINE2P
MIC2M / LINE2M
LINE1P
LEFT_LOP/M
Volume
(0 to -78dB)
LINE2
+
(R21,
Gain:
0 to -12 dB R22)
1.5dB steps
SW-Lx and SW-Rx switches
are programmed in R108
SW-R1
LINE2P
RIGHT_LOP/M
Volume
(0 to -78dB)
PGA
0/59.5dB
0.5dB steps
DAC_1
ADC_PGA
PGA_AUX
(R16)
(R89)
(R88)
(R91)
+
SW-R0
RIGHT_LOP
SW-R3
RIGHT_LOM
MIC2P / LINE2P
Bias/
Reference
Voltage Supplies
All Register Numbers are
in Decimal and in Page 0
Unless Otherwise Noted
Audio Clock
Generation
(R93)
SW-R4
LINE2M
I2C Serial
Control Bus
SCL
SDA
Reset
Reset
MICBIAS
IOVDD
DVSS
DVDD
DRVSS
DRVDD
DRVDD
AVDD
AVSS2
AVSS1
BCLK
Figure 1. Configuring TLV320AIC3109-Q1 for Bypass Path Options
While MIC1P/M inputs support eCall functionality by routing the digitized ADC output to the connectivity
module, either a dedicated MIC2P/M input or the same MIC1P/M input can be used to establish a direct
connection from microphone to the head unit for voice recognition through two different options.
1. Passive Direct Bypass: A passive direct analog bypass path from microphone inputs to line outputs.
There are two possible options:
• MIC1P/M to LEFT_LOP/ M
w 30 6C 03 // route MIC1P/M input to LEFT_LOP/M
w 30 5E 00 // power-down LEFT_LOP/M output buffer
• MIC2P/M to RIGHT_LOP/ M
w 30 6C 30 // route MIC2P/M input to RIGHT_LOP/M
w 30 5D 00 // power-down RIGHT_LOP/M output buffer
2. Active PGA Bypass: An active PGA analog bypass path with a gain stage from microphone inputs to
either line outputs, or single-ended (SE) or differential (DIFF) headphone (HP) outputs. There are four
different options:
• MIC1P/M or MIC2P/M to LEFT_LOP/ M
/*Route either MIC1P/M or MIC1P/M to PGA_AUX*/
w 30 18 00 // route differential MIC1P/input to PGA_AUX,, or
w 30 16 00 // route differential MIC2P/M input to PGA_AUX
/*Route PGA_AUX to LEFT_LOP/M*/
w 30 10 00 //unmute, 0-dB gain for PGA_AUX or
w 30 54 80 //route PGA_AUX to LEFT_LOP/M
w 30 56 0d //unmute, apply 0-dB gain, and power-up LEFT_LOP/M
2
How To Save Space And BOM Costs By Sharing Microphones Across
Automotive Subsystems
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Configuring TLV320AIC3109-Q1 for Passive Direct Bypass or Active PGA Bypass Mode
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•
•
•
MIC1P/M or MIC2P/M to RIGHT_LOP/ M
/*Route either MIC1P/M or MIC1P/M to PGA_AUX*/
w 30 18 00 // route differential MIC1P/input to PGA_AUX, or
w 30 16 00 // route differential MIC2P/M input to PGA_AUX
/*Route PGA_AUX to RIGHT_LOP/M*/
w 30 10 00 //unmute, 0-dB gain for PGA_AUX or
w 30 5b 80 //route PGA_AUX to RIGHT_LOP/M
w 30 5d 03 //unmute, apply 0-dB gain, and power-up RIGHT_LOP/M
MIC1P/M or MIC2P/M to differential HPOUT
/*Route either MIC1P/M or MIC1P/M to PGA_AUX*/
w 30 18 00 // route differential MIC1P/input to PGA_AUX, or
w 30 16 00 // route differential MIC2P/M input to PGA_AUX
/*Route PGA_AUX to RIGHT_LOP/M*/
w 30 10 00 //unmute, 0-dB gain for PGA_AUX or
w 30 26 04 //HPCOM as diff HPOUT, short-circuit protection enabled
w 30 3F 80 //route PGA_AUX to HPOUT, HPOUT gain = 0-dB
w 30 41 0B //unmute and power-up HPOUT
MIC1P/M or MIC2P/M to single-ended HPOUT
/*Route either MIC1P/M or MIC1P/M to PGA_AUX*/
w 30 18 00 // route differential MIC1P/input to PGA_AUX, or
w 30 16 00 // route differential MIC2P/M input to PGA_AUX
/*Route PGA_AUX to differential HPOUT*/
w 30 10 00 //unmute, 0-dB gain for PGA_AUX or
w 30 26 14 //HPCOM as single-ended HPOUT, short-circuit protection enabled
w 30 3F 80 //route PGA_AUX to HPOUT, HPOUT gain = 0-dB
w 30 41 0B //unmute and power-up HPOUT
Command Syntax: w [i2c address] [register] [data], where 'i2c address', 'register' and 'data' are in
hexadecimal format.
A similar microphone sharing scheme can be realized with the other TLV320AIC310x-Q1 products,
TLV320AIC3104-Q1 and TLV320AIC3106-Q1, by using appropriate device configurations.
SLAA915 – September 2019
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How To Save Space And BOM Costs By Sharing Microphones Across
Automotive Subsystems
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