lmv1024 National Semiconductor Corporation, lmv1024 Datasheet - Page 11

• Manufacturer Part Number: lmv1024
• Description: Ic Pre Amp Mic Mono Ab Adc 6usmd
• Manufacturer: National Semiconductor Corporation

Application Section
The LMV1024/LMV1026 consist of a pre-amplifier and sigma
delta converter for placement inside an electret condenser
microphone (ECM). The output of the LMV1024/LMV1026 is
a robust digital serial bit stream eliminating the sensitive low-
level analog signals of conventional JFET microphones. This
application section describes, among others, a typical appli-
cation, a sensitivity comparison between different ECM types,
stereo operation and layout recommendations on the ECM
PCBs.
BUILT-IN PRE-AMPLIFIER / ADC
The LMV1024/LMV1026 are offered in a space saving small
6-bump micro SMD package in order to fit inside small ECM
canisters. The LMV1024 or LMV1026 IC is placed on the
PCB. This PCB forms the bottom of the microphone, which is
placed in the cell phone.
Figure 3 depicts a cross section of a microphone with the IC
inside the ECM canister. The PCB of the microphone has 4
pads that connects V
FIGURE 2. Built-in Pre-Amplifier / ADC
DD
, Ground, DATA and the CLOCK.
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FIGURE 1. Typical Application
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Print Date/Time: 2009/07/20 17:12:49
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TYPICAL APPLICATION
Figure 1 depicts a typical application, where the LMV1024 or
LMV1026 is built inside the ECM canister. This ECM can be
directly connected to a DSP in a digital audio system, like a
baseband chip in a cell phone. Connecting is easy because
of the digital LMV1024/LMV1026 interface. A digital filter in
the DSP or Baseband decimates the audio signal.
FIGURE 3. Cross section of a Microphone
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