UCB1300 Просмотр технического описания (PDF) - Philips Electronics
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UCB1300 Datasheet PDF : 56 Pages
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Philips Semiconductors
Advanced modem/audio analog front-end
Preliminary specification
UCB1300
PASSIVE
UCB1300
VDDA1
17
MICP
21
ACTIVE
UCB1300
VDDA1
17
MICP
21
MICGND
20
VSSA1
18
MICGND
20
VSSA1
18
Fig.4 Possible microphone connections.
The UCB1300 audio codec input path accepts microphone signals directly, only a DC blocking capacitor is needed since
the MICP input is biased around 1.4V. The ‘ground’ side of the microphone is either connected to the analog ground
(Vssa1) or to the MICGND pin. The latter will decrease the current consumption of active microphones, since the MICGND
pin is made Hi-Z when the audio codec input path is disabled.
The full scale input voltage of the audio input path is programmable in 1.5 dB steps by setting the appropriate number in
AUDIO_GAIN[n] in the audio control register A. Using very high gains may require the use of the internal offset
cancellation circuit programmable in reg 13 to avoid clipping in the ADC.
A clip detection circuit will inform the user whenever the input voltage exceeds the maximum input voltage, since this will
lead to a high distortion. In that case AUD_CLIP_STAT in the audio control register B is set. When ACLIP_RIS_INT is
set, an interrupt is generated on the IRQOUT pin on the rising edge of the clip detect signal. When ACLIP_FAL_INT is
set, an interrupt is generated on the falling edge of the clip detect signal.
The frequency response of the audio codec depends mainly on the selected sample rate, since the bandwidth is limited
in the down and up sampling filters. These digital filters both contain several FIR and IIR low pass filters and a DC
removal filter (high pass filter). A 3rd order smoothing filter is implemented in the DAC path, between DAC and speaker
driver stage to reduce the spurious frequencies at the speaker outputs.
1999 Jul 20
9
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