LMV1091 [TI]
具有噪声抑制功能的双输入麦克风前置放大器;
| 型号： | LMV1091 |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 具有噪声抑制功能的双输入麦克风前置放大器 放大器 |
| 文件： | 总23页 (文件大小：861K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LMV1091
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SNAS481C –OCTOBER 2009–REVISED MAY 2013
LMV1091 Dual Input, Far Field Noise Suppression Microphone Amplifier
Check for Samples: LMV1091
1
FEATURES
DESCRIPTION
The LMV1091 is a fully analog dual differential input,
differential output, microphone array amplifier
designed to reduce background acoustic noise, while
2
•
•
•
•
•
•
•
•
No Loss of Voice Intelligibility
Low Power Consumption
Shutdown Function
delivering
superb
speech
clarity
in
voice
communication applications.
No added Processing Delay
Differential Outputs
The LMV1091 preserves near-field voice signals
within 4cm of the microphones while rejecting far-field
acoustic noise greater than 50cm from the
microphones. Up to 20dB of far-field rejection is
possible in a properly configured and using ±0.5dB
matched micropohones.
Adjustable 12 - 54dB Gain
Excellent RF Immunity
Available in a 25–Bump DSBGA Package
APPLICATIONS
Part of the Powerwise™ family of energy efficient
solutions, the LMV1091 consumes only 600μA of
supply current providing superior performance over
DSP solutions consuming greater than ten times the
power.
•
•
•
•
Mobile Headset
Mobile and Handheld Two-way Radios
Bluetooth and Other Powered Headsets
Hand-held Voice Microphones
The dual microphone inputs and the processed signal
output are differential to provide excellent noise
immunity. The microphones are biased with an
internal low-noise bias supply.
KEY SPECIFICATIONS
•
Far Field Noise Suppression Electrical (FFNSE
at f = 1kHz): 34dB (typ)
•
•
•
•
•
•
•
SNRIE: 26dB (typ)
Supply Voltage: 2.7V to 5.5V
Supply Current: 600μA (typ)
Standby Current: 0.1μA (typ)
Signal-to-Noise Ratio (Voice band): 65dB (typ)
Total Harmonic Distortion + Noise: 0.1% (typ)
PSRR (217Hz): 99dB (typ)
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2009–2013, Texas Instruments Incorporated
LMV1091
SNAS481C –OCTOBER 2009–REVISED MAY 2013
www.ti.com
System Diagram
Far-field noise, > 50 cm
Up to 4 cm
LMV1091
Pure analog solution
provides superior
performance over DSP
solutions
Analog
Noise
Canceling
Block
Crowd Noise
Near-Field Voice
Far field noise reduced
by up to 20 dB in properly
configured and using
+/-0.5 dB matched
microphones
+/-0.5 dB
matched
omnidirectional
microphones
Typical Application
V
DD
C
VREF
C
1
10 nF
1 mF
REF
V
DD
Mic
Bias
Bias
Mute 2
Mute 1
LPF+
R
IN3
R
IN1
1.1 kW
1.1 kW
Mic
CNTRL
*
C
IN1
Optimized
Audio
Ouput
470 nF
OUT+
LPF-
Mic2+
Mic2-
C
IN2
+
-
470 nF
C
IN3
Mic1+
Mic1-
*
470 nF
IN4
Optimized
Audio
OUT-
C
Ouput
470 nF
R
IN2
R
IN4
1.1 kW
1.1 kW
Post-Amp Gain
(6-18 dB)
Pre-Amp Gain
(6 - 36 dB)
Mode
Shutdown
GND
GA0
GA1
GA2 GA3
Mode 1
Mode 0
GB2
GB0
GB1
SD
* The value of the low-pass filter capacitor is application dependent, see the application section for additional information.
Figure 1. Typical Dual Microphone Far Field noise Cancelling Application
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Connection Diagram
1
2
3
4
Mic1+
GA1
5
Mic
Bias
A
Mic2-
Mic2+
Mode1
Mic1-
GND
REF
Mode0
Mute2
Mute1
LPF+
GA0
NC
B
C
D
E
GB0
GB1
GA2
GA3
LPF-
GB2
OUT-
VDD
_SD
OUT+
Figure 2. 25-Bump DSBGA (Top View)
See YFQ0025 Package
PIN NAME AND FUNCTION
Bump
Numbe
r
Pin Name
Pin Function
Pin Type
A1
A2
A3
A4
A5
B1
B2
B3
B4
B5
C1
C2
C3
C4
C5
D1
D2
D3
D4
D5
E1
E2
E3
E4
E5
MIC BIAS
MIC2+
MIC2–
MIC1+
MIC1–
MODE0
MODE1
GA0
Microphone Bias
Microphone 2 positive input
Microphone 2 negative input
Microphone 1 positive input
Microphone 1 negative input
Mic mode select pin
Analog Output
Analog Input
Analog Input
Analog Input
Analog Input
Digital Input
Digital Input
Digital Input
Digital Input
Ground
Mic mode select pin
Pre-Amplifier Gain select pin
Pre-Amplifier Gain select pin
Ground
GA1
GND
MUTE2
GB0
Mute select pin
Digital Input
Digital Input
Post-Amplifier Gain select pin
No Connect
NC
GA2
Pre-Amplifier Gain select pin
Reference voltage de-coupling
Mute select pin
Digital Input
Analog Ref
Digital Input
Digital Input
Digital Input
Digital Input
Supply
REF
MUTE1
GB1
Post-Amp Gain select pin
Post-Amp Gain select pin
Pre-Amp Gain select pin
Power Supply
GB2
GA3
VDD
LPF+
OUT+
OUT-
LPF-
Low pass Filter for positive output
Positive optimized audio output
Negative optimized audio output
Low pass Filter for negative output
Chip enable
Analog Input
Analog Output
Analog Output
Analog Input
Digital Input
SD
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These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings(1)(2)
Supply Voltage
6.0V
Storage Temperature
Power Dissipation(3)
ESD Rating(4)
-85°C to +150°C
Internally Limited
2000V
ESD Rating(5)
200V
CDM
500V
Junction Temperature (TJMAX
Mounting Temperature
Thermal Resistance
)
150°C
Infrared or Convection (20 sec.)
235°C
θJA (DSBGA)
70°C/W
Soldering Information See SNVA009A “microSMD Wafer Level Chip Scale Package.”
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or
other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating
Conditions indicate conditions at which the device is functional and the device should not be operated beyond such conditions. All
voltages are measured with respect to the ground pin, unless otherwise specified.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
(3) The maximum power dissipation must be de-rated at elevated temperatures and is dictated by TJMAX, θJC, and the ambient temperature
TA. The maximum allowable power dissipation is PDMAX = (TJMAX – TA) / θJA or the number given in the Absolute Maximum Ratings,
whichever is lower. For the LMV1091, TJMAX = 150°C and the typical θJA for this DSBGA package is 70°C/W. Refer to the Thermal
Considerations section for more information.
(4) Human body model, applicable std. JESD22-A114C.
(5) Machine model, applicable std. JESD22-A115-A.
Operating Ratings(1)
Supply Voltage
2.7V ≤ VDD ≤ 5.5V
TMIN ≤ TA ≤ TMAX
−40°C ≤ TA ≤ +85°C
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or
other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating
Conditions indicate conditions at which the device is functional and the device should not be operated beyond such conditions. All
voltages are measured with respect to the ground pin, unless otherwise specified.
Electrical Characteristics 3.3V(1)(2)
Unless otherwise specified, all limits ensured for TA = 25°C, VDD = 3.3V, VIN = 18mVP-P, f = 1kHz, SD = VDD, Pre Amp gain =
20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF, f = 1kHz pass through mode.
LMV1091
Typical(3) Limits(4)
Units
(Limits)
Symbol
Parameter
Conditions
VIN = 18mVP-P, A-weighted, Audio band
63
65
5
dB
dB
SNR
eN
Signal-to-Noise Ratio
Input Referred Noise level
VOUT = 18VP-P
,
voice band (300–3400Hz)
A-Weighted
μVRMS
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or
other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating
Conditions indicate conditions at which the device is functional and the device should not be operated beyond such conditions. All
voltages are measured with respect to the ground pin, unless otherwise specified.
(2) The Electrical Characteristics tables list ensured specifications under the listed Recommended Operating Conditions except as
otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and
are not ensured.
(3) Typical values represent most likely parametric norms at TA = +25°C, and at the Recommended Operation Conditions at the time of
product characterization and are not ensured.
(4) Datasheet min/max specification limits are specified by test, or statistical analysis.
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Electrical Characteristics 3.3V(1)(2) (continued)
Unless otherwise specified, all limits ensured for TA = 25°C, VDD = 3.3V, VIN = 18mVP-P, f = 1kHz, SD = VDD, Pre Amp gain =
20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF, f = 1kHz pass through mode.
VIN
Maximum Input Signal
THD+N < 1%, Pre Amp Gain = 6dB
880
1.2
820
1.1
mVP-P (min)
VRMS (min)
Differential Out+, Out-
THD+N < 1%
Maximum AC Output Voltage
VOUT
DC Level at Outputs
Total Harmonic Distortion + Noise
Input Impedance
Out+, Out-
820
0.1
mV
% (max)
kΩ
THD+N
ZIN
Differential Out+ and Out-
0.2
142
220
ZOUT
Output Impedance
Ω
RLOAD
CLOAD
10
100
kΩ (min)
pF (max)
ZLOAD
AM
Load Impedance (Out+, Out-)(5)
Minimum
Maximum
6
36
dB
dB
Microphone Preamplifier Gain Range
Microphone Preamplifier Gain
Adjustment Resolution
1.7
2.3
dB (min)
dB (max)
AMR
2
Minimum
Maximum
6
18
dB
dB
AP
Post Amplifier Gain Range
2.6
3.4
dB (min)
dB (max)
APR
Post Amplifier Gain Resolution
Far Field Noise Suppression Electrical
3
f = 1kHz (See Test Methods)
f = 300Hz (See Test Methods)
34
42
26
FFNSE
SNRIE
dB
dB
Signal-to-Noise Ratio Improvement
Electrical
f = 1kHz (See Test Methods)
f = 300Hz (See Test Methods)
26
33
18
Input Referred, Input AC grounded
fRIPPLE = 217Hz (VRIPPLE = 100mVP-P
PSRR
Power Supply Rejection Ratio
)
99
95
60
85
80
dB (min)
dB (min)
dB
fRIPPLE = 1kHz (VRIPPLE = 100mVP-P
)
CMRR
VBM
Common Mode Rejection Ratio
Microphone Bias Supply Voltage
Input referred
1.85
2.15
V (min)
V (max)
IBIAS = 1.2mA
2.0
eVBM
IDDQ
Mic bias noise voltage on VREF pin
Supply Quiescent Current
A-Weighted, CB = 10nF
VIN = 0V
7
μVRMS
0.60
0.8
mA (max)
VIN = 25mVP-P both inputs
Noise cancelling mode
IDD
Supply Current
0.60
0.1
mA
ISD
TON
TOFF
Shut Down Current
Turn-On Time(6)
Turn-Off Time(6)
SD pin = GND
0.7
40
60
μA (max)
ms (max)
ms (max)
GA0, GA1, GA2, GA3, GB0, GB1, GB2,
Mute1, Mute2,
Mode 0, Mode 1, SD
VIH
VIL
Logic High Input Threshold
Logic Low Input Threshold
1.4
0.4
V (min)
V (max)
GA0, GA1, GA2, GA3, GB0, GB1, GB2,
Mute1, Mute2,
Mode 0, Mode 1, SD
(5) Specified by design.
(6) Specified by design.
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Electrical Characteristics 5.0V(1)
Unless otherwise specified, all limits ensured for TA = 25°C, VDD = 5V, VIN = 18mVP-P, SD = VDD, Pre Amp gain = 20dB, Post
Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF, f = 1kHz pass through mode.
LMV1091
Units
(Limits)
Symbol
Parameter
Conditions
Typical(2)
Limit(3)
VIN = 18mVP-P, A-weighted, Audio band
63
dB
dB
SNR
Signal-to-Noise Ratio
VOUT = 18mVP-P
,
65
voice band (300–3400Hz)
eN
Input Referred Noise level
Maximum Input Signal
A-Weighted
5
μVRMS
VIN
THD+N < 1%
880
820
1.1
mVP-P (min)
VRMS (min)
f = 1kHz, THD+N < 1%
between differential output
Maximum AC Output Voltage
1.2
VOUT
DC Output Voltage
820
0.1
mV
% (max)
kΩ
THD+N
ZIN
Total Harmonic Distortion + Noise
Input Impedance
Differential Out+ and Out-
0.2
142
220
ZOUT
Output Impedance
Ω
Minimum
Maximum
6
36
dB
dB
AM
AMR
Microphone Preamplifier Gain Range
Microphone Preamplifier Gain
Adjustment Resolution
1.7
2.3
dB (min)
dB (max)
2
Minimum
Maximum
6
18
dB
dB
AP
Post Amplifier Gain Range
Post Amplifier Gain Adjustment
Resolution
2.6
3.4
dB (min)
dB (max)
APR
3
f = 1kHz (See Test Methods)
f = 300Hz (See Test Methods)
34
42
26
FFNSE
SNRIE
Far Field Noise Suppression Electrical
dB
dB
Signal-to-Noise Ratio Improvement
Electrical
f = 1kHz (See Test Methods)
f = 300Hz (See Test Methods)
26
33
18
Input Referred, Input AC grounded
fRIPPLE = 217Hz (VRIPPLE = 100mVP-P
PSRR
Power Supply Rejection Ratio
)
99
95
60
85
80
dB (min)
dB (min)
dB
fRIPPLE = 1kHz (VRIPPLE = 100mVP-P
)
CMRR
VBM
Common Mode Rejection Ratio
Microphone Bias Supply Voltage
Input referred
1.85
2.15
V ( min)
V (max)
IBIAS = 1.2mA
2.0
7
Microphone bias noise voltage on VREF A-Weighted, CB = 10nF
pin
μVRMS
eVBM
IDDQ
IDD
Supply Quiescent Current
VIN = 0V
0.60
0.60
0.1
0.8
mA (max)
mA
VIN = 25mVP-P both inputs
Noise cancelling mode
Supply Current
ISD
TON
TOFF
Shut Down Current
Turn On Time
SD pin = GND
μA
40
60
ms (max)
ms (max)
Turn Off Time
GA0, GA1, GA2, GA3, GB0, GB1, GB2,
Mute1, Mute2,
Mode 0, Mode 1, SD
VIH
VIL
Logic High Input Threshold
Logic Low Input Threshold
1.4
0.4
V (min)
V (max)
GA0, GA1, GA2, GA3, GB0, GB1, GB2,
Mute1, Mute2,
Mode 0, Mode 1, SD
(1) “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or
other conditions beyond those indicated in the Recommended Operating Conditions is not implied. The Recommended Operating
Conditions indicate conditions at which the device is functional and the device should not be operated beyond such conditions. All
voltages are measured with respect to the ground pin, unless otherwise specified.
(2) Typical values represent most likely parametric norms at TA = +25°C, and at the Recommended Operation Conditions at the time of
product characterization and are not ensured.
(3) Datasheet min/max specification limits are specified by test, or statistical analysis.
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Test Methods
LMV1091
Mic2+
LPF
OUT+
470 nF
Mic2-
Osc2
Osc1
AC Voltmeter
470 nF
Mic1+
470 nF
Mic1-
OUT-
470 nF
Figure 3. FFNSE, NFSLE, SNRIE Test Circuit
FAR FIELD NOISE SUPPRESSION (FFNSE)
For optimum noise suppression the far field noise should be in a broadside array configuration from the two
microphones (see Figure 20). Which means the far field sound source is equidistance from the two microphones.
This configuration allows the amplitude of the far field signal to be equal at the two microphone inputs, however a
slight phase difference may still exist. To simulate a real world application a slight phase delay was added to the
FFNSE test. The block diagram from Figure 18 is used with the following procedure to measure the FFNSE.
1. A sine wave with equal frequency and amplitude (25mVP-P) is applied to Mic1 and Mic2. Using a signal
generator, the phase of Mic 2 is delayed by 1.1° when compared with Mic1.
2. Measure the output level in dBV (X)
3. Mute the signal from Mic2
4. Measure the output level in dBV (Y)
5. FFNSE = Y - X dB
NEAR FIELD SPEECH LOSS (NFSLE)
For optimum near field speech preservation, the sound source should be in an endfire array configuration from
the two microphones (see Figure 21). In this configuration the speech signal at the microphone closest to the
sound source will have greater amplitude than the microphone further away. Additionally the signal at
microphone further away will experience a phase lag when compared with the closer microphone. To simulate
this, phase delay as well as amplitude shift was added to the NFSLE test. The schematic from Figure 18 is used
with the following procedure to measure the NFSLE.
1. A 25mVP-P and 17.25mVP-P (0.69*25mVP-P) sine wave is applied to Mic1 and Mic2 respectively. Once again,
a signal generator is used to delay the phase of Mic2 by 15.9° when compared with Mic1.
2. Measure the output level in dBV (X)
3. Mute the signal from Mic2
4. Measure the output level in dBV (Y)
5. NFSLE = Y - X dB
SIGNAL TO NOISE RATIO IMPROVEMENT ELECTRICAL (SNRIE)
The SNRIE is the ratio of FFNSE to NFSLE and is defined as:
SNRIE = FFNSE - NFSLE
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Measuring Noise and SNR
The overall noise of the LMV1091 is measured within the frequency band from 10Hz to 22kHz using an A-
weighted filter. The Mic+ and Mic- inputs of the LMV1091 are AC shorted between the input capacitors, see
Figure 4.
LMV1090
Mic2+
LPF
OUT+
A-WEIGHTED
FILTER
470 nF
short
short
AC Voltmeter
Mic2-
470 nF
Mic1+
Mic1-
470 nF
OUT-
470 nF
Figure 4. Noise Measurement Setup
For the signal to noise ratio (SNR) the signal level at the output is measured with a 1kHz input signal of 18mVP-P
using an A-weighted filter. This voltage represents the output voltage of a typical electret condenser microphone
at a sound pressure level of 94dB SPL, which is the standard level for these measurements. The LMV1091 is
programmed for 26dB of total gain (20dB preamplifier and 6dB postamplifier) with only Mic1 or Mic2 used.
The input signal is applied differentially between the Mic+ and Mic-. Because the part is in Pass Through mode
the low-pass filter at the output of the LMV1091 is disabled.
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Typical Performance Characteristics
Unless otherwise specified, TJ = 25°C, VDD = 3.3V, Input Voltage = 18mVP-P, f = 1kHz, pass through mode, Pre Amp gain =
20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF.
THD+N
vs
THD+N
vs
Frequency
Frequency
Mic1 = AC GND, Mic2 = 36mVP-P
Noise Canceling Mode
Mic2 = AC GND, Mic1 = 36mVP-P
Noise Canceling Mode
10
10
1
0.1
1
0.1
0.01
0.01
0.001
0.001
20
100
1k
10k 20k
20
100
1k
10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 5.
Figure 6.
THD+N
vs
THD+N
vs
Frequency
Frequency
Mic1 = 36mVP-P
Mic1 Pass Through Mode
Mic2 = 36mVP-P
Mic2 Pass Through Mode
10
1
10
1
0.1
0.1
0.01
0.01
0.001
0.001
20
100
1k
10k 20k
20
100
1k
10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 7.
Figure 8.
THD+N
vs
THD+N
vs
Input Voltage
Input Voltage
Mic1 = AC GND, f = 1kHz
Mic2 Noise Canceling Mode
Mic2 = AC GND, f = 1kHz
Mic1 Noise Canceling Mode
100
10
100
10
1
0.1
1
0.1
0.01
0.001
0.01
0.001
0.01
0.1
1
0.01
0.1
1
INPUT VOLTAGE (V
)
P-P
INPUT VOLTAGE (V
)
P-P
Figure 9.
Figure 10.
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Typical Performance Characteristics (continued)
Unless otherwise specified, TJ = 25°C, VDD = 3.3V, Input Voltage = 18mVP-P, f = 1kHz, pass through mode, Pre Amp gain =
20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF.
THD+N
vs
THD+N
vs
Input Voltage
f = 1kHz
Input Voltage
f = 1kHz
Mic1 Pass Through Mode
Mic2 Pass Through Mode
100
10
100
10
1
0.1
1
0.1
0.01
0.001
0.01
0.001
0.01
0.1
1
0.01
0.1
1
INPUT VOLTAGE (V
)
INPUT VOLTAGE (V
)
P-P
P-P
Figure 11.
Figure 12.
PSRR
vs
Frequency
PSRR
vs
Frequency
Pre Amp Gain = 20dB, Post Amp Gain = 6dB
VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND
Mic1 Pass Through Mode
Pre Amp Gain = 20dB, Post Amp Gain = 6dB
VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND
Mic2 Pass Through Mode
+0
+0
-10
-20
-10
-20
-30
-30
-40
-40
-50
-50
-60
-60
-70
-70
-80
-80
-90
-90
-100
-110
-100
-110
20
100
1k
10k 20k
20
100
1k
10k 20k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 13.
Figure 14.
PSRR
vs
Frequency
Pre Amp Gain = 20dB, Post Amp Gain = 6dB
VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND
Noise Canceling Mode
Far Field Noise Suppression Electrical
vs
Frequency
60
+0
-10
-20
50
40
30
20
10
0
-30
-40
-50
-60
-70
-80
-90
-100
-110
20
100
1k
10k 20k
100
1k
10k
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 15.
Figure 16.
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Typical Performance Characteristics (continued)
Unless otherwise specified, TJ = 25°C, VDD = 3.3V, Input Voltage = 18mVP-P, f = 1kHz, pass through mode, Pre Amp gain =
20dB, Post Amp gain = 6dB, RL = 100kΩ, and CL = 4.7pF.
Signal-to-Noise Ratio Electrical
vs
Frequency
35
30
25
20
15
10
5
0
100
1k
10k
FREQUENCY (Hz)
Figure 17.
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APPLICATION DATA
INTRODUCTION
The LMV1091 is a fully analog single chip solution to reduce the far field noise picked up by microphones in a
communication system. A simplified block diagram is provided in Figure 18.
Preamp Gain
(6 dB - 36 dB)
Post Amp Gain
(6 dB - 18 dB)
Mic1
Mic2
OUT+
OUT-
Analog
Noise
Cancelling
Block
Optimized
Audio
Ouput
Figure 18. Simplified Block Diagram of the LMV1091
The output signal of the microphones is amplified by a pre-amplifier with adjustable gain between 6dB and 36dB.
After the signals are matched the analog noise cancelling suppresses the far field noise signal. The output of the
analog noise cancelling processor is amplified in the post amplifier with adjustable gain between 6dB and 18dB.
For optimum noise and EMI immunity, the microphones have a differential connection to the LMV1091 and the
output of the LMV1091 is also differential. The adjustable gain functions can be controlled via GA0–GA3 and
GB0–GB2 pins.
Power Supply Circuits
A low drop-out (LDO) voltage regulator in the LMV1091 allows the device to be independent of supply voltage
variations.
The Power On Reset (POR) circuitry in the LMV1091 requires the supply voltage to rise from 0V to VDD in less
than 100ms.
The Mic Bias output is provided as a low noise supply source for the electret microphones. The noise voltage on
the Mic Bias microphone supply output pin depends on the noise voltage on the internal the reference node. The
de-coupling capacitor on the VREF pin determines the noise voltage on this internal reference. This capacitor
should be larger than 1nF; having a larger capacitor value will result in a lower noise voltage on the Mic Bias
output.
Gain Balance and Gain Budget
In systems where input signals have a high dynamic range, critical noise levels or where the dynamic range of
the output voltage is also limited, careful gain balancing is essential for the best performance. Too low of a gain
setting in the preamplifier can result in higher noise levels while too high of a gain setting in the preamplifier will
result in clipping and saturation in the noise cancelling processor and output stages.
The gain ranges and maximum signal levels for the different functional blocks are shown in Figure 19. Two
examples are given as a guideline on how to select proper gain settings.
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Pre Amp
Gain
(6 dB - 36 dB)
Gain
(Max. 0 dB)
Post Amp Gain
(6 dB - 18 dB)
OUT+
OUT-
Analog
Noise
Cancelling
Block
Mic1
or
Mic2
Optimized
Audio
Ouput
Maximum
AC Input
Voltage
Maximum
AC Input
Voltage
Maximum
AC Intput
Voltage
Maximum
AC Output
Voltage
<440 mVpp
<1.6 Vpp
<1.6 Vpp
<3.2 Vpp
Figure 19. Maximum Signal Levels
Example 1
An application using microphones with 50mVP-P maximum output voltage, and a baseband chip after the
LMV1091 with 1.5VP-P maximum input voltage.
For optimum noise performance, the gain of the input stage should be set to the maximum.
1. 50mVP-P +36dB = 3.1VP-P
.
2. 3.1VP-P is higher than the maximum 1.5VP-P allowed for the Noise Cancelling Block (NCB). This means a
gain lower than 29.5dB should be selected.
3. Select the nearest lower gain from the gain settings shown in Table 1, 28dB is selected. This will prevent the
NCB from being overloaded by the microphone. With this setting, the resulting output level of the Pre
Amplifier will be 1.26VP-P
.
4. The NCB has a gain of 0dB which will result in 1.26VP-P at the output of the LMV1091. This level is less than
maximum level that is allowed at the input of the post amp of the LMV1091.
5. The baseband chip limits the maximum output voltage to 1.5VP-P with the minimum of 6dB post amp gain,
this results in requiring a lower level at the input of the post amp of 0.75VP-P. Now calculating this for a
maximum preamp gain, the output of the preamp must be no more than 0.75mVP-P
6. Calculating the new gain for the preamp will result in <23.5dB gain.
7. The nearest lower gain will be 22dB.
.
So using preamp gain = 22dB and postamp gain = 6dB is the optimum for this application.
Example 2
An application using microphones with 10mVP-P maximum output voltage, and a baseband chip after the
LMV1091 with 3.3VP-P maximum input voltage.
For optimum noise performance we would like to have the maximum gain at the input stage.
1. 10mVP-P + 36dB = 631mVP-P
.
2. This is lower than the maximum 1.5VP-P, so this is OK.
3. The NCB has a gain of 0dB which will result in 1.5VP-P at the output of the LMV1091. This level is lower than
the maximum level that is allowed at the input of the Post Amp of the LMV1091.
4. With a Post Amp gain setting of 6dB the output of the Post Amp will be 3VP-P which is OK for the baseband.
5. The nearest lower Post Amp gain will be 6dB.
So using preamp gain = 36dB and postamp gain = 6dB is optimum for this application.
Pre-Amp/Post-Amp Gains
The Pre-amplifier gain of the LMV1091TM can be controlled using the GA0-GA3 pins. See Table 1 below for
Pre-amplifier gain control. The Post-Amp gain can be controlled using the GB0-GB2 pins. See Table 2 below for
Post-amplifier gain control.
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Table 1. Mic Pre-Amp Gain Settings
GA3
0
GA2
0
GA1
0
GA0
0
Pre-Amplifier Gain
6dB
0
0
0
1
8dB
0
0
1
0
10dB
0
0
1
1
12dB
0
1
0
0
14dB
0
1
0
1
16dB
0
1
1
0
18dB
0
1
1
1
20dB
1
0
0
0
22dB
1
0
0
1
24dB
1
0
1
0
26dB
1
0
1
1
28dB
1
1
0
0
30dB
1
1
0
1
32dB
1
1
1
0
34dB
1
1
1
1
36dB
Table 2. Post-Amp Gain Settings
GB2
GB1
GB0
Post-Amplifier Gain
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
6dB
9dB
12dB
15dB
18dB
18dB
18dB
18dB
Noise Reduction Mode Settings
The LMV1091TM has four mode settings. It can be placed in noise cancellation mode, mic 1 on with mic 2 off,
mic 1 off with mic 2 on, and mic1 and mic2. See Table 3 for control settings.
Table 3. Noise Reduction Mode Settings
Mode 1
Mode 0
Noise Reduction Mode Selection
Noise cancelling mode
Only Mic 1 On
0
0
1
1
0
1
0
1
Only Mic 2 On
Mic 1 + Mic 2
Mute Section
Mic 1 and Mic 2 can be muted independently, using the Mute 1 and Mute 2 pins. See Table 4 for control settings.
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Table 4. Noise Reduction Mode Settings
Mute 2
Mute 1
Mute Mode Selection
Mic 1 an Mic 2 on
Mic 1 mute
0
0
1
1
0
1
0
1
Mic 2 mute
Mic 1 and Mic 2 mute
Microphone Placement
Because the LMV1091 is a microphone array Far Field Noise Reduction solution, proper microphone placement
is critical for optimum performance. Two things need to be considered: The spacing between the two
microphones and the position of the two microphones relative to near field source
If the spacing between the two microphones is too small near field speech will be canceled along with the far
field noise. Conversely, if the spacing between the two microphones is large, the far field noise reduction
performance will be degraded. The optimum spacing between Mic 1 and Mic 2 is 1.5-2.5cm. This range provides
a balance of minimal near field speech loss and maximum far field noise reduction. The microphones should be
in line with the desired sound source 'near speech' and configured in an endfire array (see Figure 21) orientation
from the sound source. If the 'near speech' (desired sound source) is equidistant to the source like a broadside
array (see Figure 20) the result will be a great deal of near field speech loss.
NEAR
SPEECH
OPTIMIZED
SPEECH
LMV1091
WRONG
Figure 20. Broadside Array (WRONG)
OPTIMIZED
SPEECH
1.5~2.5 cm
LMV1091
CORRECT
Figure 21. Endfire Array (CORRECT)
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Low-Pass Filter At The Output
At the output of the LMV1091 there is a provision to create a 1st order low-pass filter (only enabled in 'Noise
Cancelling' mode). This low-pass filter can be used to compensate for the change in frequency response that
results from the noise cancellation process. The change in frequency response resembles a first-order high-pass
filter, and for many of the applications it can be compensated by a first-order low-pass filter with cutoff frequency
between 1.5kHz and 2.5kHz.
The transfer function of the low-pass filter is derived as:
Post Amplifier gain
H(s) =
sRfCf+1
(1)
This low-pass filter is created by connecting a capacitor between the LPF pin and the OUT pin of the LMV1091.
The value of this capacitor also depends on the selected output gain. For different gains the feedback resistance
in the low-pass filter network changes as shown in Table 5.
This will result in the following values for a cutoff frequency of 2000 Hz:
Table 5. Low-Pass Filter Capacitor For 2kHz
Post Amplifier Gain Setting (dB)
Rf (kΩ)
20
Cf (nF)
3.9
6
9
29
2.7
12
15
18
40
2.0
57
1.3
80
1.0
A-Weighted Filter
The human ear is sensitive for acoustic signals within a frequency range from about 20Hz to 20kHz. Within this
range the sensitivity of the human ear is not equal for each frequency. To approach the hearing response,
weighting filters are introduced. One of those filters is the A-weighted filter.
The A-weighted filter is used in signal to noise measurements, where the wanted audio signal is compared to
device noise and distortion.
The use of this filter improves the correlation of the measured values to the way these ratios are perceived by
the human ear.
10
0
-10
-20
-30
-40
-50
-60
-70
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 22. A-Weighted Filter
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Table 6. Revision History
Rev
Date
Description
1.0
10/28/09
Initial released.
Changed the unit measure of the X1, X2, and X3 (under the Physical Dimension)
from mm to μm.
1.01
05/17/10
1.02
C
01/13/11
05/02/13
Fixed typos on Figure 1 (Typical Application diagram).
Changed layout of National Data Sheet to TI format
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status Package Type Package Pins Package
Eco Plan
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
Samples
Drawing
Qty
(1)
(2)
(3)
(4/5)
(6)
LMV1091TM/NOPB
LMV1091TMX/NOPB
ACTIVE
ACTIVE
DSBGA
DSBGA
YFQ
YFQ
25
25
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
Level-1-260C-UNLIM
-40 to 85
-40 to 85
ZA4
ZA4
3000 RoHS & Green
SNAGCU
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.
(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
(6)
Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two
lines if the finish value exceeds the maximum column width.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
5-Nov-2021
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
B0
K0
P1
W
Pin1
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
LMV1091TM/NOPB
LMV1091TMX/NOPB
DSBGA
DSBGA
YFQ
YFQ
25
25
250
178.0
178.0
8.4
8.4
2.18
2.18
2.18
2.18
0.76
0.76
4.0
4.0
8.0
8.0
Q1
Q1
3000
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
5-Nov-2021
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
LMV1091TM/NOPB
LMV1091TMX/NOPB
DSBGA
DSBGA
YFQ
YFQ
25
25
250
208.0
208.0
191.0
191.0
35.0
35.0
3000
Pack Materials-Page 2
MECHANICAL DATA
YFQ0025xxx
D
0.600
±0.075
E
TMD25XXX (Rev C)
D: Max = 2.04 mm, Min = 1.98 mm
E: Max = 2.04 mm, Min = 1.98 mm
4215084/A
12/12
A. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.
B. This drawing is subject to change without notice.
NOTES:
www.ti.com
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IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD
PARTY INTELLECTUAL PROPERTY RIGHTS.
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