LMV1091TM/NOPB - NATIONAL SEMICONDUCTOR

LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

LMV1091 Dual Input, Far Field Noise Suppression Microphone Amplifier

Check for Samples: LMV1091

1FEATURES DESCRIPTION

The LMV1091 is a fully analog dual differential input,

2• No Loss of Voice Intelligibility differential output, microphone array amplifier

• Low Power Consumption designed to reduce background acoustic noise, while

• 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

• Adjustable 12 - 54dB Gain acoustic noise greater than 50cm from the

• Excellent RF Immunity microphones. Up to 20dB of far-field rejection is

• Available in a 25–Bump DSBGA Package possible in a properly configured and using ±0.5dB

matched micropohones.

APPLICATIONS Part of the Powerwise™ family of energy efficient

• Mobile Headset solutions, the LMV1091 consumes only 600μA of

supply current providing superior performance over

• Mobile and Handheld Two-way Radios DSP solutions consuming greater than ten times the

• Bluetooth and Other Powered Headsets power.

• Hand-held Voice Microphones The dual microphone inputs and the processed signal

output are differential to provide excellent noise

KEY SPECIFICATIONS immunity. The microphones are biased with an

internal low-noise bias supply.

• 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)

1Please 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.

2All trademarks are the property of their respective owners.

Products conform to specifications per the terms of the Texas

Instruments standard warranty. Production processing does not

necessarily include testing of all parameters.

* The value of the low-pass filter capacitor is application dependent, see the application section for additional information.

VDD

GND

Mic

Bias

REF

Mic1+

1.1 k:1.1 k:

VDD

1 PF

C110 nF

CVREF

RIN3 RIN1

CIN1

Mic2+

470 nF

CIN3

CIN4

CIN2 Mic2-

470 nF

Mic1-

470 nF

RIN2

RIN4

Bias

Mute 1

Mute 2

GA0 GA1 GA2 GA3

Mode

Mode 0

Shutdown

SD Mode 1

Mic

CNTRL

Post-Amp Gain

(6-18 dB)

GB0 GB1 GB2

Pre-Amp Gain

(6 - 36 dB)

Optimized

Audio

Ouput

OUT-

LPF-

Optimized

Audio

Ouput

OUT+

LPF+

+/-0.5 dB

matched

omnidirectional

microphones

Analog

Noise

Canceling

Block

LMV1091

Near-Field Voice

Loud Music

Traffic Noise

Crowd Noise

Announcements

Machine Noise

Near-Field Voice

Far-field noise, > 50 cm Up to 4 cm

Pure analog solution

provides superior

performance over DSP

solutions

Far field noise reduced

by up to 20 dB in properly

configured and using

+/-0.5 dB matched

microphones

LMV1091

SNAS481C –OCTOBER 2009–REVISED MAY 2013

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System Diagram

Typical Application

Figure 1. Typical Dual Microphone Far Field noise Cancelling Application

Product Folder Links: LMV1091

1 432

Mic

Bias Mic2+ Mic2- Mic1+ Mic1-

Mode0

Mute2

Mute1

LPF+

Mode1

GB0

GB1

OUT+

GB2

GA0

OUT- LPF- _SD

VDD

REF

GND

GA1

GA2

GA3

LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

Connection Diagram

Figure 2. 25-Bump DSBGA (Top View)

See YFQ0025 Package

PIN NAME AND FUNCTION

Bump

Numbe Pin Name Pin Function Pin Type

A1 MIC BIAS Microphone Bias Analog Output

A2 MIC2+ Microphone 2 positive input Analog Input

A3 MIC2– Microphone 2 negative input Analog Input

A4 MIC1+ Microphone 1 positive input Analog Input

A5 MIC1– Microphone 1 negative input Analog Input

B1 MODE0 Mic mode select pin Digital Input

B2 MODE1 Mic mode select pin Digital Input

B3 GA0 Pre-Amplifier Gain select pin Digital Input

B4 GA1 Pre-Amplifier Gain select pin Digital Input

B5 GND Ground Ground

C1 MUTE2 Mute select pin Digital Input

C2 GB0 Post-Amplifier Gain select pin Digital Input

C3 NC No Connect

C4 GA2 Pre-Amplifier Gain select pin Digital Input

C5 REF Reference voltage de-coupling Analog Ref

D1 MUTE1 Mute select pin Digital Input

D2 GB1 Post-Amp Gain select pin Digital Input

D3 GB2 Post-Amp Gain select pin Digital Input

D4 GA3 Pre-Amp Gain select pin Digital Input

D5 VDD Power Supply Supply

E1 LPF+ Low pass Filter for positive output Analog Input

E2 OUT+ Positive optimized audio output Analog Output

E3 OUT- Negative optimized audio output Analog Output

E4 LPF- Low pass Filter for negative output Analog Input

E5 SD Chip enable Digital Input

Product Folder Links: LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

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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 -85°C to +150°C

Power Dissipation(3) Internally Limited

ESD Rating(4) 2000V

ESD Rating(5) 200V

CDM 500V

Junction Temperature (TJMAX) 150°C

Mounting Temperature Infrared or Convection (20 sec.) 235°C

Thermal Resistance 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 Units

Symbol Parameter Conditions (Limits)

Typical(3) Limits(4)

VIN = 18mVP-P, A-weighted, Audio band 63 dB

SNR Signal-to-Noise Ratio VOUT = 18VP-P,65 dB

voice band (300–3400Hz)

eNInput Referred Noise level A-Weighted 5 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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SNAS481C –OCTOBER 2009–REVISED MAY 2013

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 880 820 mVP-P (min)

Differential Out+, Out-

Maximum AC Output Voltage 1.2 1.1 VRMS (min)

THD+N < 1%

VOUT DC Level at Outputs Out+, Out- 820 mV

THD+N Total Harmonic Distortion + Noise Differential Out+ and Out- 0.1 0.2 % (max)

ZIN Input Impedance 142 kΩ

ZOUT Output Impedance 220 Ω

RLOAD 10 kΩ(min)

ZLOAD Load Impedance (Out+, Out-)(5) CLOAD 100 pF (max)

Minimum 6 dB

AMMicrophone Preamplifier Gain Range Maximum 36 dB

Microphone Preamplifier Gain 1.7 dB (min)

AMR 2

Adjustment Resolution 2.3 dB (max)

Minimum 6 dB

APPost Amplifier Gain Range Maximum 18 dB

2.6 dB (min)

APR Post Amplifier Gain Resolution 3 3.4 dB (max)

f = 1kHz (See Test Methods) 34 26

FFNSEFar Field Noise Suppression Electrical dB

f = 300Hz (See Test Methods) 42

Signal-to-Noise Ratio Improvement f = 1kHz (See Test Methods) 26 18

SNRIEdB

Electrical f = 300Hz (See Test Methods) 33

Input Referred, Input AC grounded

PSRR Power Supply Rejection Ratio fRIPPLE = 217Hz (VRIPPLE = 100mVP-P) 99 85 dB (min)

fRIPPLE = 1kHz (VRIPPLE = 100mVP-P) 95 80 dB (min)

CMRR Common Mode Rejection Ratio Input referred 60 dB

1.85 V (min)

VBM Microphone Bias Supply Voltage IBIAS = 1.2mA 2.0 2.15 V (max)

eVBM Mic bias noise voltage on VREF pin A-Weighted, CB= 10nF 7 μVRMS

IDDQ Supply Quiescent Current VIN = 0V 0.60 0.8 mA (max)

VIN = 25mVP-P both inputs

IDD Supply Current 0.60 mA

Noise cancelling mode

ISD Shut Down Current SD pin = GND 0.1 0.7 μA (max)

TON Turn-On Time(6) 40 ms (max)

TOFF Turn-Off Time(6) 60 ms (max)

GA0, GA1, GA2, GA3, GB0, GB1, GB2,

VIH Logic High Input Threshold Mute1, Mute2, 1.4 V (min)

Mode 0, Mode 1, SD

GA0, GA1, GA2, GA3, GB0, GB1, GB2,

VIL Logic Low Input Threshold Mute1, Mute2, 0.4 V (max)

Mode 0, Mode 1, SD

(5) Specified by design.

(6) Specified by design.

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

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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

Symbol Parameter Conditions (Limits)

Typical(2) Limit(3)

VIN = 18mVP-P, A-weighted, Audio band 63 dB

SNR Signal-to-Noise Ratio VOUT = 18mVP-P,65 dB

voice band (300–3400Hz)

eNInput Referred Noise level A-Weighted 5 μVRMS

VIN Maximum Input Signal THD+N < 1% 880 820 mVP-P (min)

f = 1kHz, THD+N < 1% VRMS (min)

Maximum AC Output Voltage 1.2 1.1

between differential output

VOUT DC Output Voltage 820 mV

THD+N Total Harmonic Distortion + Noise Differential Out+ and Out- 0.1 0.2 % (max)

ZIN Input Impedance 142 kΩ

ZOUT Output Impedance 220 Ω

Minimum 6 dB

AMMicrophone Preamplifier Gain Range Maximum 36 dB

Microphone Preamplifier Gain 1.7 dB (min)

AMR 2

Adjustment Resolution 2.3 dB (max)

Minimum 6 dB

APPost Amplifier Gain Range Maximum 18 dB

Post Amplifier Gain Adjustment 2.6 dB (min)

APR 3

Resolution 3.4 dB (max)

f = 1kHz (See Test Methods) 34 26

FFNSEFar Field Noise Suppression Electrical dB

f = 300Hz (See Test Methods) 42

Signal-to-Noise Ratio Improvement f = 1kHz (See Test Methods) 26 18

SNRIEdB

Electrical f = 300Hz (See Test Methods) 33

Input Referred, Input AC grounded

PSRR Power Supply Rejection Ratio fRIPPLE = 217Hz (VRIPPLE = 100mVP-P) 99 85 dB (min)

fRIPPLE = 1kHz (VRIPPLE = 100mVP-P) 95 80 dB (min)

CMRR Common Mode Rejection Ratio Input referred 60 dB

1.85 V ( min)

VBM Microphone Bias Supply Voltage IBIAS = 1.2mA 2.0 2.15 V (max)

Microphone bias noise voltage on VREF A-Weighted, CB= 10nF 7 μVRMS

eVBM pin

IDDQ Supply Quiescent Current VIN = 0V 0.60 0.8 mA (max)

VIN = 25mVP-P both inputs

IDD Supply Current 0.60 mA

Noise cancelling mode

ISD Shut Down Current SD pin = GND 0.1 μA

TON Turn On Time 40 ms (max)

TOFF Turn Off Time 60 ms (max)

GA0, GA1, GA2, GA3, GB0, GB1, GB2,

VIH Logic High Input Threshold Mute1, Mute2, 1.4 V (min)

Mode 0, Mode 1, SD

GA0, GA1, GA2, GA3, GB0, GB1, GB2,

VIL Logic Low Input Threshold Mute1, Mute2, 0.4 V (max)

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.

Product Folder Links: LMV1091

Mic2+

Mic2-

Mic1+

Mic1-

470 nF

OUT-

LPF

LMV1091

OUT+

Osc2

Osc1

AC Voltmeter

LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

Test Methods

Figure 3. FFNSE, NFSLE, SNRIETest 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

FFNSEtest. 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-XdB

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 NFSLEtest. 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-XdB

SIGNAL TO NOISE RATIO IMPROVEMENT ELECTRICAL (SNRIE)

The SNRIEis the ratio of FFNSEto NFSLEand is defined as:

SNRIE= FFNSE- NFSLE

Product Folder Links: LMV1091

A-WEIGHTED

FILTER

Mic2+

Mic2-

Mic1+

Mic1-

470 nF

OUT-

LPF

LMV1090

short

AC Voltmeter

OUT+

LMV1091

SNAS481C –OCTOBER 2009–REVISED MAY 2013

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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.

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.

Product Folder Links: LMV1091

0.01

100

0.1

0.001 10.01 0.1

INPUT VOLTAGE (VP-P)

THD+N (%)

0.01

100

0.1

0.001 10.01 0.1

INPUT VOLTAGE (VP-P)

THD+N (%)

0.001

0.01

0.1

THD+N (%)

FREQUENCY (Hz)

20 20k

100 1k 10k

0.001

0.01

0.1

THD+N (%)

FREQUENCY (Hz)

20 20k

100 1k 10k

0.001

0.01

0.1

THD+N (%)

FREQUENCY (Hz)

20 20k

100 1k 10k

0.001

0.01

0.1

FREQUENCY (Hz)

20 20k100 1k 10k

THD+N (%)

LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

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 THD+N

vs vs

Frequency Frequency

Mic1 = AC GND, Mic2 = 36mVP-P Mic2 = AC GND, Mic1 = 36mVP-P

Noise Canceling Mode Noise Canceling Mode

Figure 5. Figure 6.

THD+N THD+N

vs vs

Frequency Frequency

Mic1 = 36mVP-P Mic2 = 36mVP-P

Mic1 Pass Through Mode Mic2 Pass Through Mode

Figure 7. Figure 8.

THD+N THD+N

vs vs

Input Voltage Input Voltage

Mic1 = AC GND, f = 1kHz Mic2 = AC GND, f = 1kHz

Mic2 Noise Canceling Mode Mic1 Noise Canceling Mode

Figure 9. Figure 10.

Product Folder Links: LMV1091

100 1k 10k

FREQUENCY (Hz)

FFNSE (Hz)

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

PSRR (dB)

FREQUENCY (Hz)

20 20k

100 1k 10k

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

PSRR (dB)

FREQUENCY (Hz)

20 20k100 1k 10k

-110

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

PSRR (dB)

FREQUENCY (Hz)

20 20k100 1k 10k

0.01

100

0.1

0.001 10.01 0.1

INPUT VOLTAGE (VP-P)

THD+N (%)

0.01

100

0.1

0.001 10.01 0.1

INPUT VOLTAGE (VP-P)

THD+N (%)

LMV1091

SNAS481C –OCTOBER 2009–REVISED MAY 2013

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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 THD+N

vs vs

Input Voltage Input Voltage

f = 1kHz f = 1kHz

Mic1 Pass Through Mode Mic2 Pass Through Mode

Figure 11. Figure 12.

PSRR PSRR

vs vs

Frequency Frequency

Pre Amp Gain = 20dB, Post Amp Gain = 6dB Pre Amp Gain = 20dB, Post Amp Gain = 6dB

VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND

Mic1 Pass Through Mode Mic2 Pass Through Mode

Figure 13. Figure 14.

PSRR

Frequency

Pre Amp Gain = 20dB, Post Amp Gain = 6dB Far Field Noise Suppression Electrical

VRIPPLE = 100mVP-P, Mic1 = Mic2 = AC GND vs

Noise Canceling Mode Frequency

Figure 15. Figure 16.

Product Folder Links: LMV1091

100 1k 10k

FREQUENCY (Hz)

SNRIE (Hz)

LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

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

Frequency

Figure 17.

Product Folder Links: LMV1091

Analog

Noise

Cancelling

Block

Optimized

Audio

Ouput

OUT+

Post Amp Gain

(6 dB - 18 dB)

Preamp Gain

(6 dB - 36 dB)

Mic1

OUT-

Mic2

LMV1091

SNAS481C –OCTOBER 2009–REVISED MAY 2013

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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.

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.

Product Folder Links: LMV1091

Analog

Noise

Cancelling

Block

Optimized

Audio

Ouput

OUT+

Post Amp Gain

(6 dB - 18 dB)

Pre Amp

Gain

(6 dB - 36 dB)

Mic1

Mic2

Gain

(Max. 0 dB)

OUT-

Maximum

AC Input

Voltage

<1.6 Vpp

Maximum

AC Output

Voltage

<3.2 Vpp

Maximum

AC Input

Voltage

<440 mVpp

Maximum

AC Intput

Voltage

<1.6 Vpp

LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

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.

Product Folder Links: LMV1091

LMV1091

SNAS481C –OCTOBER 2009–REVISED MAY 2013

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Table 1. Mic Pre-Amp Gain Settings

GA3 GA2 GA1 GA0 Pre-Amplifier Gain

0 0 0 0 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 6dB

0 0 1 9dB

0 1 0 12dB

0 1 1 15dB

1 0 0 18dB

1 0 1 18dB

1 1 0 18dB

1 1 1 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

0 0 Noise cancelling mode

0 1 Only Mic 1 On

1 0 Only Mic 2 On

1 1 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.

Product Folder Links: LMV1091

LMV1091

NEAR

SPEECH

CORRECT

1.5~2.5 cm OPTIMIZED

SPEECH

LMV1091

NEAR

SPEECH

WRONG

OPTIMIZED

SPEECH

LMV1091

www.ti.com

SNAS481C –OCTOBER 2009–REVISED MAY 2013

Table 4. Noise Reduction Mode Settings

Mute 2 Mute 1 Mute Mode Selection

0 0 Mic 1 an Mic 2 on

0 1 Mic 1 mute

1 0 Mic 2 mute

1 1 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.

Figure 20. Broadside Array (WRONG)

Figure 21. Endfire Array (CORRECT)

Product Folder Links: LMV1091

10 100 1k 10k 100k

FREQUENCY (Hz)

-70

-60

-50

-40

-30

-20

-10

dBV

H(s) =

Post Amplifier gain

sRfCf+1

LMV1091

SNAS481C –OCTOBER 2009–REVISED MAY 2013

www.ti.com

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:

(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) Cf(nF)

6 20 3.9

9 29 2.7

12 40 2.0

15 57 1.3

18 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.

Figure 22. A-Weighted Filter

Product Folder Links: LMV1091

LMV1091

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SNAS481C –OCTOBER 2009–REVISED MAY 2013

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)

1.01 05/17/10 from mm to μm.

1.02 01/13/11 Fixed typos on Figure 1 (Typical Application diagram).

C 05/02/13 Changed layout of National Data Sheet to TI format

Product Folder Links: LMV1091

PACKAGE OPTION ADDENDUM

www.ti.com 10-Dec-2020

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status

(1)

Package Type Package

Drawing Pins Package

Qty Eco Plan

(2)

Lead finish/

Ball material

(6)

MSL Peak Temp

(3)

Op Temp (°C) Device Marking

(4/5)

Samples

LMV1091TM/NOPB ACTIVE DSBGA YFQ 25 250 RoHS & Green SNAGCU Level-1-260C-UNLIM -40 to 85 ZA4

LMV1091TMX/NOPB ACTIVE DSBGA YFQ 25 3000 RoHS & Green SNAGCU Level-1-260C-UNLIM -40 to 85 ZA4

(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.

PACKAGE OPTION ADDENDUM

www.ti.com 10-Dec-2020

Addendum-Page 2

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device Package

Type Package

Drawing Pins SPQ Reel

Diameter

(mm)

Reel

Width

W1 (mm)

(mm) B0

(mm) K0

(mm) P1

(mm) W

(mm) Pin1

Quadrant

LMV1091TM/NOPB DSBGA YFQ 25 250 178.0 8.4 2.18 2.18 0.76 4.0 8.0 Q1

LMV1091TMX/NOPB DSBGA YFQ 25 3000 178.0 8.4 2.18 2.18 0.76 4.0 8.0 Q1

PACKAGE MATERIALS INFORMATION

www.ti.com 8-May-2013

Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

LMV1091TM/NOPB DSBGA YFQ 25 250 210.0 185.0 35.0

LMV1091TMX/NOPB DSBGA YFQ 25 3000 210.0 185.0 35.0

PACKAGE MATERIALS INFORMATION

www.ti.com 8-May-2013

Pack Materials-Page 2

MECHANICAL DATA

YFQ0025xxx

www.ti.com

TMD25XXX (Rev C)

. All linear dimensions are in millimeters. Dimensioning and tolerancing per ASME Y14.5M-1994.

B. This drawing is subject to change without notice.

NOTES:

4215084/A 12/12

0.600

±0.075

D: Max =

E: Max =

2.04 mm, Min =

1.98 mm

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