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High Quality Mode
-20
Low Power Mode
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-100
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-140
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FREQUENCY (Hz)
Figure 8. Power Supply Rejection (PSR) vs. Frequency
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Center Frequency of 5kz Band, Hz
Figure 10. Typical Ultrasonic SNR, Ultrasonic Mode
5. THEORY OF OPERATION
5.1. PDM DATA FORMAT
The output from the DATA pin of the T5837 is in pulse density modulated (PDM) format. This data is the 1-bit
output of a 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 the right, can drive a single DATA line. See Figure 1 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
11Figure 12 shows a diagram of the two stereo channels sharing a common DATA line.
Document Number: DS-000447
Revision: 1.2
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0
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FREQUENCY (kHz)
Figure 9. Typical Ultrasonic Frequency Response,
Ultrasonic Mode
T5837
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