NSC LMV1032-06 Amplifiers for 3 wire analog electret microphone Datasheet

LMV1032-06/LMV1032-15/LMV1032-25
Amplifiers for 3 Wire Analog Electret Microphones
General Description
Features
The LMV1032 is an audio amplifier series for small form
factor electret microphones. It is designed to replace the
JFET preamp currently being used. The LMV1032 series is
ideal for extended battery life applications, such as a bluetooth communication link. The addition of a third pin in
electret microphones that incorporate the LMV1032 allows
for a dramatic reduction in supply current as compared to the
JFET equipped electret microphone. Microphone supply current is thus reduced to 60 µA, assuring longer battery life.
The LMV1032 series is guaranteed for supply voltages from
1.7V to 5V, and has fixed voltage gains of 6 dB, 15 dB and 25
dB.
(Typical LMV1032-06, 1.7V Supply; Unless Otherwise
Noted)
n Output voltage noise (A-weighted)
−97 dBV
n Low supply current
60 µA
n Supply voltage
1.7V to 5V
n PSRR
84 dB
n Signal to noise ratio
58 dB
n Input capacitance
2 pF
> 100 MΩ
n Input impedance
< 200Ω
n Output impedance
n Max input signal
300 mVPP
n Temperature range
−40˚C to 85˚C
n Offered in 1.13 x 1.13 x 0.4mm Ultra Thin micro SMD
lead free (NOPB) package
The LMV1032 series offers low output impedance over the
voice bandwidth, excellent power supply rejection (PSRR),
and stability over temperature.
The devices are offered in space saving 4-bump ultra thin
micro SMD (TM) lead free package and are thus ideally
suited for the form factor of miniature electret microphone
packages.
Block Diagram
Applications
n
n
n
n
n
Mobile communications - Bluetooth
Automotive accessories
Cellular phones
PDAs
Accessory microphone products
Electret Microphone
20084202
20084201
© 2005 National Semiconductor Corporation
DS200842
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LMV1032-06/LMV1032-15/LMV1032-25 Amplifiers for 3 Wire Analog Electret Microphones
March 2005
LMV1032-06/LMV1032-15/LMV1032-25
Absolute Maximum Ratings (Note 1)
Storage Temperature Range
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Junction Temperature (Note 6)
−65˚C to 150˚C
150˚C max
Mounting Temperature
Infrared or Convection (20 sec.)
235˚C
ESD Tolerance (Note 2)
Human Body Model
2500V
Machine Model
Operating Ratings (Note 1)
250V
Supply Voltage
Supply Voltage
VDD - GND
1.7V to 5V
Temperature Range
5.5V
−40˚C to +85˚C
1.7V and 5V Electrical Characteristics
(Note 3)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C and VDD = 1.7V and 5V. Boldface limits apply at the temperature extremes.
Symbol
Parameter
Min
(Note 4)
Conditions
Typ
(Note 5)
Max
(Note 4)
60
85
100
IDD
Supply Current
VIN = GND
SNR
Signal to Noise Ratio
VDD = 1.7V
VIN = 18 mVPP
f = 1 kHz
LMV1032-06
58
LMV1032-15
61
LMV1032-25
61
VDD = 5V
VIN = 18 mVPP
f = 1 kHz
LMV1032-06
59
LMV1036-15
61
1.7V < VDD < 5V
LMV1032-06
65
60
75
LMV1032-15
60
55
70
LMV1032-25
55
50
65
PSRR
VIN
Power Supply Rejection Ratio
Max Input Signal
f = 1kHz and THD+N
< 1%
fLOW
Lower −3 dB Roll Off Frequency
RSOURCE = 50Ω
VIN = 18 mVPP
fHIGH
Upper −3 dB Roll Off Frequency
RSOURCE = 50Ω
VIN = 18 mVPP
en
Output Noise
LMV1032-25
62
LMV1032-06
300
LMV1032-15
170
LMV1032-25
60
LMV1032-06
120
LMV1032-15
75
LMV1032-25
21
LMV1032-06
−97
LMV1032-15
−89
LMV1032-25
VOUT
Output Voltage
VIN = GND
dB
mVPP
kHz
dBV
−80
100
300
500
LMV1032-15
250
500
750
LMV1032-25
300
600
1000
< 200
Output Impedance
f = 1 kHz
IO
Output Current
VDD = 1.7V, VOUT = 1.7V, Sinking
0.9
0.5
2.3
VDD = 1.7V, VOUT = 0V, Sourcing
0.3
0.2
0.64
VDD = 5V, VOUT = 1.7V, Sinking
0.9
0.5
2.4
VDD = 5V, VOUT = 0V, Sourcing
0.4
0.1
1.46
2
Hz
LMV1032-06
RO
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µA
dB
70
A-Weighted
Units
mV
Ω
mA
(Note 3) (Continued)
Unless otherwise specified, all limits guaranteed for TJ = 25˚C and VDD = 1.7V and 5V. Boldface limits apply at the temperature extremes.
Symbol
THD
CIN
Parameter
Total Harmonic Distortion
Min
(Note 4)
Conditions
f = 1 kHz
VIN = 18 mVPP
LMV1032-06
0.11
LMV1032-15
0.13
LMV1032-25
0.35
Input Capacitance
ZIN
Input Impedance
AV
Gain
Typ
(Note 5)
Max
(Note 4)
%
2
pF
> 100
f = 1 kHz
VIN = 18 mVPP
Units
MΩ
LMV1032-06
5.5
4.5
6.2
6.7
7.7
LMV1032-15
14.8
14
15.4
16
17
LMV1032-25
24.8
24
25.5
26.2
27
dB
Note 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 guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2: Human Body Model (HBM) is 1.5 kΩ in series with 100 pF.
Note 3: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of
the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ > TA.
Note 4: All limits are guaranteed by design or statistical analysis.
Note 5: Typical values represent the most likely parametric norm.
Note 6: 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 into a PC board.
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LMV1032-06/LMV1032-15/LMV1032-25
1.7V and 5V Electrical Characteristics
LMV1032-06/LMV1032-15/LMV1032-25
Connection Diagram
4-Bump Ultra Thin micro SMD
20084203
Top View
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.
Ordering Information
Package
Part Number
LMV1032UP-06
LMV1032UPX-06
4-Bump Ultra Thin
micro SMD lead free
LMV1032UP-15
LMV1032UPX-15
LMV1032UP-25
LMV1032UPX-25
Package Marking
Date Code
Date Code
Date Code
Note: The LMV1032 series is offered only with lead free (NOPB) solder bumps.
The LMV1032 series replaces the LMV1014.
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Transport Media
NSC Drawing
250 Units Tape and Reel
3k Units Tape and Reel
250 Units Tape and Reel
3k Units Tape and Reel
250 Units Tape and Reel
3k Units Tape and Reel
UPA04QQA
Unless otherwise specified, VS = 1.7V, single supply, TA =
Supply Current vs. Supply Voltage (LMV1032-06)
Supply Current vs. Supply Voltage (LMV1032-15)
20084204
20084213
Closed Loop Gain and Phase vs. Frequency
(LMV1032-06)
Supply Current vs. Supply Voltage (LMV1032-25)
20084205
20084214
Closed Loop Gain and Phase vs. Frequency
(LMV1032-15)
Closed Loop Gain and Phase vs. Frequency
(LMV1032-25)
20084216
20084215
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LMV1032-06/LMV1032-15/LMV1032-25
Typical Performance Characteristics
25˚C
LMV1032-06/LMV1032-15/LMV1032-25
Typical Performance Characteristics Unless otherwise specified, VS = 1.7V, single supply, TA =
25˚C (Continued)
Power Supply Rejection Ratio vs. Frequency
(LMV1036-06)
Power Supply Rejection Ratio vs. Frequency
(LMV1032-15)
20084206
20084217
Power Supply Rejection Ratio vs. Frequency
(LMV1032-25)
Total Harmonic Distortion vs. Frequency (LMV1032-06)
20084207
20084218
Total Harmonic Distortion vs. Frequency (LMV1032-15)
Total Harmonic Distortion vs. Frequency (LMV1032-25)
20084219
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20084220
6
Total Harmonic Distortion vs. Input Voltage
(LMV1032-06)
Total Harmonic Distortion vs. Input Voltage
(LMV1032-15)
20084208
20084221
Total Harmonic Distortion vs. Input Voltage
(LMV1032-25)
Output Voltage Noise vs. Frequency (LMV1032-06)
20084223
20084222
Output Voltage Noise vs. Frequency (LMV1032-15)
Output Voltage Noise vs. Frequency (LMV1032-25)
20084224
20084225
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LMV1032-06/LMV1032-15/LMV1032-25
Typical Performance Characteristics Unless otherwise specified, VS = 1.7V, single supply, TA =
25˚C (Continued)
LMV1032-06/LMV1032-15/LMV1032-25
Application Section
LOW CURRENT
The LMV1032 has low supply current for a longer battery life.
The low supply current makes this amplifier suitable for
microphone applications which need to be always on.
BUILT IN GAIN
The LMV1032 is offered in space saving small micro SMD
package in order to fit in the metal can of a microphone. The
LMV1032 is 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 inside the metal
can via the PCB to the microphone.
20084209
FIGURE 2. A-Weighted Filter
MEASURING NOISE AND SNR
The overall noise of the LMV1032 is measured within the
frequency band from 10 Hz to 22 kHz using an A-weighted
filter. The input of the LMV1032 is connected to ground with
a 5 pF capacitor.
20084202
FIGURE 1. Built-in Gain
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.
The A-weighted filter is usually 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.
20084210
FIGURE 3. Noise Measurement Setup
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 SPL. No input capacitor is
connected.
SOUND PRESSURE LEVEL
The volume of sound applied to a microphone is usually
stated as a pressure level referred to the threshold of hearing of the human ear. The 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 (20µPa)
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 referred
to 1 Pascal (Pa).
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LMV1032-06/LMV1032-15/LMV1032-25
Application Section
(Continued)
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.
20084212
FIGURE 5. Gain vs. Frequency Over Temperature
The LMV1032 is optimized to be used in audio band applications. By using the LMV1032, the gain response is flat
within the audio band and has the linearity and temperature
stability.
ADVANTAGE OF THREE PINS
The LMV1032 ECM solution has three pins instead of two
pins as in the case of a JFET solution. The third pin provides
the advantage of a low supply current, high PSRR and
eliminates the need for additional components.
Noise pick-up by a microphone in a cell phone is a wellknown problem. A conventional JFET circuit is sensitive for
noise pick-up because of its high output impedance. The
output impedance is usually around 2.2 kΩ. By providing
separate output and supply pins a much lower output impedance is achieved and therefore is less sensitive to noise
pick-up.
RF noise is amongst other caused by non-linear behavior.
The non-linear behavior of the amplifier at high frequencies,
well above the usable bandwidth of the device, causes AMdemodulation of high frequency signals. The AM modulation
contained in such signals folds back into the audio band,
thereby disturbing the intended microphone signal. The
GSM signal of a cell phone is such an AM-modulated signal.
The modulation frequency of 216 Hz and its harmonics can
be observed in the audio band. This type of noise is called
bumblebee noise.
20084211
FIGURE 4. dB SPL to dBV Conversion
Example: Busy traffic is 70 dB SPL
VOUT = 70 −94 −44 = −68 dBV
This is equivalent to 1.13 mVPP
Since the LMV1032-06 has a gain of 2 (6 dB) over the JFET,
the output voltage of the microphone is 2.26 mVPP. By
implementing the LMV1032-06, the sensitivity of the microphone is −38 dBV/Pa (−44 + 6).
LOW FREQUENCY CUT OFF FILTER
To reduce noise on the output of the microphone a low cut
filter has been implemented. This filter reduces the effect of
wind and handling noise.
It’s also helpful 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.
EXTERNAL PRE-AMPLIFIER APPLICATION
The LMV1032 can also be used outside of an ECM as a
space saving external pre-amplifier. In this application, the
LMV1032 follows a phantom biased JFET microphone in the
circuit (Figure 6). The input of the LMV1032 is connected to
the microphone via the 2.2 µF capacitor. The advantage of
this circuit versus one with only a JFET microphone are the
additional gain and the high pass filter of the LMV1032. The
high pass filter makes the output signal more robust and less
sensitive to low frequency disturbances. The LMV1032
should be placed as close as possible to the microphone.
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LMV1032-06/LMV1032-15/LMV1032-25
Application Section
(Continued)
20084226
FIGURE 6. LMV1032 as external pre-amplifier
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LMV1032-06/LMV1032-15/LMV1032-25
Physical Dimensions
inches (millimeters)
unless otherwise noted
NOTE: UNLESS OTHERWISE SPECIFIED.
1. TITANIUM COATING.
2. FOR SOLDER BUMP COMPOSITION, SEE "SOLDER INFORMATION" IN THE PACKAGING SECTION OF THE NATIONAL SEMICONDUCTOR WEB
PAGE (www.national.com).
3. RECOMMEND NON-SOLDER MASK DEFINED LANDING PAD.
4. PIN A1 IS ESTABLISHED BY LOWER LEFT CORNER WITH RESPECT TO TEXT ORIENTATION.
5. XXX IN DRAWING NUMBER REPRESENTS PACKAGE SIZE VARIATION WHERE X1 IS PACKAGE WIDTH, X2 IS PACKAGE LENGTH AND X3 IS
PACKAGE HEIGHT.
6. REFERENCE JEDEC REGISTRATION MO-211. VARIATION BC.
4-Bump Ultra Thin micro SMD
NS Package Number UPA04QQA
X1 = 1.133mm X2 = 1.133mm X3 = 0.4mm
11
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LMV1032-06/LMV1032-15/LMV1032-25 Amplifiers for 3 Wire Analog Electret Microphones
Notes
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
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