PCM1860 Datasheet, PDF (41/115 Pages) Texas Instruments – 4ch Audio ADCs With Universal Front End

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PCM1860, PCM1862, PCM1864, PCM1864-Q1
SLASE55A – NOVEMBER 2014 – REVISED DECEMBER 2014
1 msec
Interval Time (X sec)
Figure 35. Energysense Signal Wakeup Logic
There is a balance between lowest frequency detectable, and time on that particular channel. There are three
options in register SIGDET_INT_INTVL (Page.0 0x36):
• 50 Hz detect (160 ms per channel)
• 100 Hz detect (80 ms per channel)
• 200 Hz detect (40 ms per channel)
10.14.2.1 Energysense Threshold Levels for both Signal Loss and Signal Detect
There are two threshold levels used for Energysense. One is the loss of signal level, another one is the resume
of signal level.
RESUME Level
LOSS Level
Figure 36. Dual Thresholds for Energysense
As both thresholds are DSP based, their coefficients are stored in virtual coefficient space that is programmed
through the device register map.
For example, to change the resume threshold value to –30dB (0x040C37):
Write 0x00 0x01 ; # change to register page 1
Write 0x02 0x2D ; # write the memory address of resume threshold
Write 0x04 0x04 ; # bit[23:15]
Write 0x05 0x0C ; # bit[15:8]
Write 0x06 0x37 ; # bit[7:0]
Write 0x01 0x01 ; # execute write operation
10.14.3 Programming Various Coefficients for Energysense
Programming the DSP coefficients for the Energysense secondary ADC is done through the indirect virtual
programming registers in Page1. The Low Pass Filter (LPF) and High Pass filter (HPF) coefficients can be
written to flatten out the frequency response, as well as the Energysense Loss and Resume thresholds. Visually,
one can imagine the DSP flow as shown in Figure 37.
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