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PDF LMV1012 Data sheet ( Hoja de datos )
| Número de pieza | LMV1012 | |
| Descripción | Pre-Amplified ICs for High Gain 2-Wire Microphones | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LMV1012 (archivo pdf) en la parte inferior de esta página. Total 15 Páginas | ||
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August 2004
LMV1012 Analog Series:
Pre-Amplified IC’s for High Gain 2-Wire Microphones
General Description
The LMV1012 is an audio amplifier series for small form
factor electret microphones. This 2-wire portfolio is designed
to replace the JFET amplifier currently being used. The
LMV1012 series is ideally suited for applications requiring
high signal integrity in the presence of ambient or RF noise,
such as in cellular communications. The LMV1012 audio
amplifiers are guaranteed to operate over a 2.2V to 5.0V
supply voltage range with fixed gains of 7.8 dB, 15.6 dB,
20.9 dB, and 23.8 dB. The devices offer excellent THD, gain
accuracy and temperature stability as compared to a JFET
microphone.
The LMV1012 series enables a two-pin electret microphone
solution, which provides direct pin-to-pin compatibility with
the existing JFET market.
The devices are offered in extremely thin space saving
4-bump micro SMD packages. The LMV1012XP is designed
for 1.0 mm canisters and thicker ECM canisters. These
extremely miniature packages are designed for electret con-
denser microphones (ECM) form factor.
Features
(Typical LMV1012-15, 2.2V supply, RL = 2.2 kΩ, C = 2.2 µF,
VIN = 18 mVPP, unless otherwise specified)
n Supply voltage
2V - 5V
n Supply current
<180 µA
n Signal to noise ratio (A-weighted)
60 dB
n Output voltage noise (A-weighted)
−89 dBV
n Total harmonic distortion
0.09%
n Voltage gain
— LMV1012-07
7.8 dB
— LMV1012-15
15.6 dB
— LMV1012-20
20.9 dB
— LMV1012-25
23.8 dB
n Temperature range
−40˚C to 85˚C
n Offered in 4-bump micro SMD packages
Applications
n Cellular phones
n Headsets
n Mobile communications
n Automotive accessories
n PDAs
n Accessory microphone products
Schematic Diagram
Built-In Gain Electret Microphone
20058701
© 2004 National Semiconductor Corporation DS200587
20058702
www.national.com
1 page  
Connection Diagram
4-Bump micro SMD
Top View
20058703
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
4-Bump Extreme Thin
micro SMD
(0.3 mm max height)
lead free only
4-Bump Ultra-Thin
micro SMD
(0.4 mm max height)
lead free only
4-Bump Thin
micro SMD
(0.5 mm max height)
Part Number
LMV1012XP-15
LMV1012XPX-15
LMV1012XP-25
LMV1012XPX-25
LMV1012UP-07
LMV1012UPX-07
LMV1012UP-15
LMV1012UPX-15
LMV1012UP-20
LMV1012UPX-20
LMV1012UP-25
LMV1012UPX-25
LMV1012TP-07
LMV1012TPX-07
LMV1012TP-15
LMV1012TPX-15
LMV1012TP-25
LMV1012TPX-25
Package Marking
Date Code
Date Code
Date Code
Transport Media
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
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
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
NSC Drawing
XPA04HLA
UPA04GKA
TPA04GKA
5 www.national.com
5 Page 
Application Section (Continued)
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).
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 conven-
tional microphone has a sensitivity of -44 dBV/Pa.
amplified which gives a bass sound. This amplification can
cause an overload, which results in a distortion of the signal.
20058711
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 LMV1012-15 has a gain of 6 (15.6 dB) over the
JFET, the output voltage of the microphone is 6.78 mVPP. By
implementing the LMV1012-15, the sensitivity of the micro-
phone is -28.4 dBV/Pa (−44 + 15.6).
LOW FREQUENCY CUT OFF FILTER
To reduce noise on the output of the microphone a low
frequency cut off 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
20058712
FIGURE 5. LMV1012-15 Gain vs. Frequency Over
Temperature
The LMV1012 is optimized to be used in audio band appli-
cations. By using the LMV1012, the gain response is flat
within the audio band and has linearity and temperature
stability Figure 5.
NOISE
Noise pick-up by a microphone in cell phones is a well-
known problem. A conventional JFET circuit is sensitive for
noise pick-up because of its high output impedance, which is
usually around 2.2 kΩ.
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 AM-
demodulation 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 kind of noise is called
bumblebee noise.
RF noise caused by a GSM signal can be reduced by
connecting two external capacitors to ground, see Figure 6.
One capacitor reduces the noise caused by the 900 MHz
carrier and the other reduces the noise caused by 1800/
1900 MHz.
11 www.national.com
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet LMV1012.PDF ] | |
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