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| 型號(hào)： | EVAL-ADMP521Z |
| 廠商： | Analog Devices Inc |
| 文件頁(yè)數(shù)： | 17/17頁(yè) |
| 文件大?。?/td> | 0K |
| 描述： | BOARD EVAL FOR ADMP521Z |
| 標(biāo)準(zhǔn)包裝： | 1 |
| 系列： | iMEMS® |
| 主要目的： | 音頻，MEMS 全向麥克風(fēng) |
| 嵌入式： | 否 |
| 已用 IC / 零件： | ADMP521 |
| 主要屬性： | 數(shù)字輸出 |
| 已供物品： | 板 |
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ADMP521
Data Sheet
Rev. A | Page 8 of 16
THEORY OF OPERATION
PDM DATA FORMAT
The output from the DATA pin of the ADMP521 is in PDM
format. This data is the 1-bit output of a fourth-order Σ-Δ
modulator. The data is encoded so that the left channel is clocked
on the falling edge of CLK and the right channel is clocked on
the rising edge of CLK. After driving the DATA signal high or
low in the appropriate half frame of the CLK signal, the DATA
driver of the microphone tristates. In this way, two microphones,
one set to the left channel and the other to right, can drive a
single DATA line. See Figure 3 for a timing diagram of the PDM
data format; the DATA1 and DATA2 lines shown in this figure are
two halves of the single physical DATA signal. Figure 10 shows a
diagram of the two stereo channels sharing a common DATA line.
If only one microphone is connected to the DATA signal, the
output is only clocked on a single edge (see Figure 9). For example,
a left channel microphone is never clocked on the rising edge of
CLK. In a single microphone application, each bit of the DATA
signal is typically held for the full CLK period until the next
transition because the leakage of the DATA line is not enough
to discharge the line while the driver is tristated.
See Table 6 for the channel assignments according to the logic
level on the L/R SELECT pin.
Table 6. ADMP521 Channel Setting
L/R SELECT Setting
Channel
Low (tie to ground)
DATA1 (right)
High (tie to VDD)
DATA2 (left)
For PDM data, the density of the pulses indicates the signal
amplitude. A high density of high pulses indicates a signal near
positive full scale and a high density of low pulses indicates a signal
near negative full scale. A perfect zero (dc) audio signal shows
an alternating pattern of high and low pulses.
The output PDM data signal has a small dc offset of between 3% to
7% of full scale. This dc signal is typically removed by a high-pass
filter in the codec that is connected to the digital microphone.
DATA1 (R)
CLK
DATA
10141-
012
Figure 9. Mono PDM Format
DATA2 (L)
DATA1 (R)
CLK
DATA
10141-
013
Figure 10. Stereo PDM Format
PDM MICROPHONE SENSITIVITY
The acoustic input levels of the microphone in dB SPL are rms
measurements; however, the sensitivity and output level of a
digital microphone is given as a peak level. This is because its
output is referenced to the full-scale digital word, which is a
peak value. This convention is different from the output levels
of analog microphones, which are given as an rms voltage. The
ADMP521 has a sensitivity of 26 dBFS. A 94 dB SPL (rms) input
signal gives a 26 dBFS peak output level; therefore, the rms
level of this digital output is 29 dBFS.
This convention of using peak levels to specify the output of
digital microphones must be kept in mind when configuring
downstream signal processing that may rely on precise signal
levels. For example, dynamic range processors (compressors,
limiters, noise gates) typically set thresholds based on rms
signal levels; therefore, adjust the signals of the microphone
from peak to rms by lowering the dBFS value by 3 dB.
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| EVAL-ADMP521Z-FLEX | 功能描述:BOARD EVAL FOR ADMP521Z RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評(píng)估演示板和套件 系列:iMEMS® 標(biāo)準(zhǔn)包裝:1 系列:PSoC® 主要目的:電源管理，熱管理 嵌入式:- 已用 IC / 零件:- 主要屬性:- 次要屬性:- 已供物品:板，CD，電源 |
| EVAL-ADMP522Z-FLEX | 制造商:InvenSense Inc 功能描述:ADMP522 - Flexible Evaluation Board, Bulk 制造商:Analog Devices 功能描述:ADMP522 MEMS MICROPHONE EVAL 制造商:Analog Devices 功能描述:ADMP522, MEMS MICROPHONE, EVAL BOARD 制造商:Analog Devices 功能描述:EB Omnidirectional Microphone -PDM 制造商:Analog Devices 功能描述:EVAL BOARD, ADMP522 MEMS MICROPHONE, Silicon Manufacturer:Analog Devices, Silicon Core Number:ADMP522, Kit Application Type:Audio, Video, Application Sub Type:MEMS Microphone, Kit Contents:Eval Board ADMP522 |
| EVAL-ADMP621Z-FLEX | 制造商:AD 制造商全稱:Analog Devices 功能描述:Wide Dynamic Range Microphone with PDM Digital Output |
| EVAL-ADN2525-NTZ | 制造商:Analog Devices 功能描述:OPTICAL EVAL KIT FOR THE ADN2525 - Bulk |
| EVAL-ADN2525-OPZ | 制造商:Analog Devices 功能描述:OPTICAL EVALUATION KIT FOR THE ADN2525 制造商:Analog Devices 功能描述:OPTICAL EVAL KIT FOR THE ADN2525 - Bulk |
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