LMV1031
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SNOSAP8B – SEPTEMBER 2005 – REVISED MAY 2013
LMV1031-20 Amplifier for Internal 3-Wire Analog Microphones and External Preamplifier
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FEATURES
DESCRIPTION
•
The LMV1031 audio amplifier is an ideal replacement
for the JFET preamplifier that is currently used in the
electret microphones. The LMV1031 is optimized for
applications that require extended battery life, such
as Bluetooth communication links. The supply current
for the LMV1031 is only 72 μA. This is a dramatic
reduction from that required for a JFET equipped
microphone. The LMV1031, with its separate output
and supply pins, offers a higher PSRR and eliminates
the need for additional external components.
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2
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•
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•
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(Typical LMV1031-20, 2V Supply; Unless
Otherwise Noted)
Signal to Noise Ratio 62 dB
Output Voltage Noise (A-Weighted) −86 dBV
Low Supply Current 72 μA
Supply Voltage 2V to 5V
Input Impedance >100 MΩ
Max Input Signal 108 mVPP
Output Voltage 1.09V
Temperature Range −40°C to 85°C
Large Dome 4-Bump DSBGA Package with
Improved Adhesion Technology
The LMV1031 has less than 200Ω of output
impedance over the full audio bandwidth. The gain
response of the LMV1031 is flat within the audio band
and is stable over the temperature range.
APPLICATIONS
•
•
•
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The LMV1031 is ensured to operate from 2V to 5V
supply voltage over the full temperature range, has a
fixed voltage gain of 20 dB and enhanced SNR
performance. The LMV1031 is optimized for an
output biasing of 1.09V.
Mobile Communications - Bluetooth
Accessory Microphone Products
Cellular Phones
PDAs
The LMV1031 is available in a large dome 4-bump
ultra thin DSBGA package that can easily fit on the
PCB inside the miniature microphone metal can
(package). This package is designed for microphone
PCBs requiring 1 kg adhesion criteria.
Block Diagram
Electret Microphone
DIAPHRAGM
VDD
xx
xxx
x
x
ELECTRET
VIN
VOUT
1x
GAIN
CONNECTOR
x
x
IC
VDC
x
GND
AIRGAP
BACKPLATE
LMV1031
VCC
x
VOUT
GND
1
2
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.
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 © 2005–2013, Texas Instruments Incorporated
LMV1031
SNOSAP8B – SEPTEMBER 2005 – 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)
Human Body Model
ESD Tolerance (3)
2500V
Machine Model
250V
Supply Voltage VDD - GND
5.5V
−65°C to 150°C
Storage Temperature Range
Junction Temperature (4)
150°C max
Mounting Temperature
(1)
(2)
(3)
(4)
Infrared or Convection (20 sec.)
235°C
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For specified specifications and the test
conditions, see the Electrical Characteristics.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
The human body model (HBM) is 1.5 kΩ in series with 100 pF. The machine model is 0Ω in series with 200 pF.
The maximum power dissipation is a function of TJ(MAX) , θJA and TA. The maximum allowable power dissipation at any ambient
temperature is PD = (TJ(MAX) - TA)/θJA. All numbers apply for packages soldered directly onto a PC board.
Operating Ratings (1)
Supply Voltage
2V to 5V
−40°C to +85°C
Temperature Range
(1)
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For specified specifications and the test
conditions, see the Electrical Characteristics.
2V and 5V Electrical Characteristics (1)
Unless otherwise specified, all limits are specified for TJ = 25°C and VDD = 2V and 5V. Boldface limits apply at the
temperature extremes.
Symbol
Parameter
Conditions
Min (2)
Typ (3)
Max (2)
Units
72
90
100
μA
IDD
Supply Current
VIN = GND
SNR
Signal to Noise Ratio
f = 1 kHz, VIN = 18 mVPP
62
THD
Total Harmonic Distortion
f = 1 kHz, VIN = 18 mVPP
0.18
%
en
Output Noise
A-Weighted
−86
dBV
AV
Gain
f = 1 kHz, VIN = 18 mVPP
fLOW
Lower −3 dB Roll Off Frequency
RSOURCE = 50Ω, VIN = 18 mVPP
72
Hz
fHIGH
Upper −3 dB Roll Off Frequency
RSOURCE = 50Ω, VIN = 18 mVPP
52
kHz
VIN
Max Input Signal
f = 1 kHz and THD+N < 1%
108
mVPP
ZIN
Input Impedance
>100
MΩ
CIN
Input Capacitance
Output Voltage
VIN = GND
RO
Output Impedance
f = 1 kHz
PSRR
Power Supply Rejection Ratio
2V < VDD < 5V
(2)
(3)
2
20.1
20.90
21.00
2
VOUT
(1)
19.18
19.00
dB
890
875
1090
dB
pF
1310
1325
mV
TA.
All limits are specified by design or statistical analysis.
Typical values represent the most likely parametric norm at the time of characterization.
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Connection Diagram
A2
OUTPUT
X
A1
GND
B2
VCC
B1
INPUT
Note:
- Pin numbers are referenced to package marking text orientation.
- The actual physical placement of the package marking will vary slightly from part to part. The package will designate
the date code and will vary considerably. Package marking does not correlate to device type in any way.
Figure 1. 4-Bump Ultra Thin DSBGA
Top View
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LMV1031
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Typical Performance Characteristics
Unless otherwise specified, VS = 2V, single supply, TA = 25°C
Supply Current vs. Supply Voltage
Output Voltage vs. Supply Voltage
Figure 2.
Figure 3.
Gain vs. Supply Voltage
Closed Loop Gain and Phase
vs. Frequency
25
200
100
GAIN
15
0
10
-100
PHASE (o)
GAIN (dB)
20
PHASE
-200
5
0
10
100
1k
10k
100k
-300
1M
FREQUENCY (Hz)
4
Figure 4.
Figure 5.
Power Supply Rejection Ratio
vs. Frequency
Total Harmonic Distortion
vs. Frequency
Figure 6.
Figure 7.
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Typical Performance Characteristics (continued)
Unless otherwise specified, VS = 2V, single supply, TA = 25°C
Total Harmonic Distortion
vs. Input Voltage
Output Voltage Noise
vs. Frequency
Figure 8.
Figure 9.
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LMV1031
SNOSAP8B – SEPTEMBER 2005 – REVISED MAY 2013
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APPLICATION SECTION
LOW CURRENT
The LMV1031 has a low supply current which allows for a longer battery life. The low supply current of 72 μA
makes this amplifier optimal for microphone applications which need to be always on.
BUILT-IN GAIN
The LMV1031 is offered in the space saving small DSBGA package which fits perfectly into the metal can of a
microphone. This allows the LMV1031 to be placed on the PCB inside the microphone.
The bottom side of the PCB has the pins that connect the supply voltage to the amplifier and make the output
available. The input of the amplifier is connected to the microphone via the PCB.
DIAPHRAGM
xx
xxx
x
x
ELECTRET
AIRGAP
BACKPLATE
CONNECTOR
x
x
IC
x
LMV1031
VCC
x
VOUT
GND
Figure 10. Built-in Gain
EXTERNAL PREAMPLIFIER APPLICATION
The LMV1031 can also be used outside of an ECM as a space saving external preamplifier. In this application,
the LMV1031 follows a phantom biased JFET microphone in the circuit. This is shown in Figure 11. The input of
the LMV1031 is connected to the microphone via a 2.2 µF capacitor. The advantages of this circuit over one with
only a JFET microphone are the additional gain and the high pass filter supplied by the LMV1031. The high pass
filter makes the output signal more robust and less sensitive to low frequency disturbances. In this configuration
the LMV1031 should be placed as close as possible to the microphone.
VDD
VDD
2.2 k:
VDD
VIN
2.2 PF
JFET
Microphone
VOUT
VOUT
GND
LMV1031
GND
Figure 11. LMV1031 as external preamplifier
6
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A-WEIGHTED FILTER
The human ear has a frequency range from 20 Hz to about 20 kHz. 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.
10
0
-10
dBV
-20
-30
-40
-50
-60
-70
10
1k
100
100k
10k
FREQUENCY (Hz)
Figure 12. A-Weighted Filter
The A-weighted filter is commonly used in signal-to-noise ratio measurements, where sound is compared to
device noise. It improves the correlation of the measured data to the signal-to-noise ratio perceived by the
human ear.
OUTPUT CURRENT
The LMV1031 is designed for driving high ohmic loads with several milli amperes of output current. Figure 13
shows the gain performance of the LMV1031 versus the sinking and sourcing current. The gain remains constant
within the shown output current range. This sets the operating range of the LMV1031 with respect to the output
current.
2.0
NEGATIVE = SOURCING CURRENT
POSITIVE = SINKING CURRENT
20
1.5
GAIN (dB)
GAIN
1.0
15
VOUT
10
0.5
5
0.0
0
-2.0
OUTPUT VOLTAGE (V)
25
-0.5
-1.0
0.0
1.0
2.0
3.0
4.0
OUTPUT CURRENT (mA)
Figure 13. Performance vs. Output Current
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LMV1031
SNOSAP8B – SEPTEMBER 2005 – REVISED MAY 2013
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MEASURING NOISE AND SNR
The overall noise of the LMV1031 is measured within the frequency band from 10 Hz to 22 kHz using an Aweighted filter. The input of the LMV1031 is connected to ground with a 5 pF capacitor.
A-WEIGHTED FILTER
5pF
Figure 14. Noise Measurement Setup
The signal-to-noise ratio (SNR) is measured with a 1 kHz input signal of 18 mVPP using an A-weighted filter. This
represents a sound pressure level of 94 dB with a standard ECM sensitivity. No input capacitor is connected.
SOUND PRESSURE LEVEL
The volume of sound applied to a microphone is commonly stated as the pressure level with respect to the
threshold of hearing of the human ear. This sound pressure level (SPL) in decibels is defined by:
Sound pressure level (dB) = 20 log Pm/PO
where
•
•
Pm is the measured sound pressure
PO is the threshold of hearing (20 µPa)
In order to be able to calculate the resulting output voltage of the microphone for a given SPL, the sound
pressure in dB SPL needs to be converted to the absolute sound pressure in dBPa. This is the sound pressure
level in decibels which is referred to 1 Pascal (Pa).
The conversion is given by:
dBPa = dB SPL + 20*log 20 µPa
dBPa = dB SPL - 94 dB
Translation from absolute sound pressure level to a voltage is specified by the sensitivity of the microphone. A
conventional microphone has a sensitivity of −44 dBV/Pa.
ABSOLUTE
SOUND
PRESSURE
[dBPa]
-94dB
SENSITIVITY
[dBV/Pa]
SOUND
PRESSURE
[dB SPL]
VOLTAGE
[dBV]
Figure 15. dB SPL to dBV Conversion
8
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SNOSAP8B – SEPTEMBER 2005 – REVISED MAY 2013
Example: Busy traffic is 70 dB
VOUT = 70 −94 −44 = −68 dBV
This is equivalent to 1.13 mVPP
Since the LMV1031-20 has a gain of 10 times (20 dB) over the JFET, the output voltage of the microphone is
11.3 mVPP. By replacing the JFET with the LMV1031-20, the sensitivity of the microphone is −24 dBV/Pa (−44 +
20).
LOW FREQUENCY CUT-OFF FILTER
The LMV1031 has a low cut-off filter on the output of the microphone, to reduce low frequency noises, such as
wind and vibration. This also helps to reduce the proximity effect in directional microphones. This effect occurs
when the sound source is very close to the microphone. The lower frequencies are amplified which gives a bass
sound. This amplification can cause an overload, which results in a distortion of the signal.
Figure 16. Gain vs. Frequency
The LMV1031 is optimized to be used in audio band applications. As shown in Figure 16, the LMV1031 provides
a flat gain response within the audio band and offers excellent temperature stability.
ADVANTAGE OF THREE PINS
When implemented in an Electret Condenser Microphone (ECM) the LMV1031 adds the advantages of a three
pin configuration. The third pin provides a low supply current, higher PSRR, and eliminates the need for
additional external components.
It is well known that cell phone microphones are sensitive to noise pick-up. A conventional JFET circuit is
sensitive to noise pick-up because of its high output impedance, which is usually around 2.2 kΩ. The LMV1031 is
less sensitive to noise pick-up because it provides separate output and supply pins. Using separate pins greatly
reduces the output impedance.
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LMV1031
SNOSAP8B – SEPTEMBER 2005 – REVISED MAY 2013
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REVISION HISTORY
Changes from Revision A (May 2013) to Revision B
•
10
Page
Changed layout of National Data Sheet to TI format ............................................................................................................ 9
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
(3)
Device Marking
(4/5)
(6)
LMV1031UR-20/NOPB
ACTIVE
DSBGA
YPD
4
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
LMV1031URX-20/NOPB
ACTIVE
DSBGA
YPD
4
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 85
(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
