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
TELECOM CODEC
The telecom codec contains an input channel, built up from a 64 times oversampling sigma delta analog to digital
converter (ADC) with digital decimation filters, programmable attenuationgain and built-in sidetone suppression circuit.
The output path consist of a digital up sample filter, a 64 time oversampling 4 bit digital to analog converter (DAC) circuit
followed by a differential output driver, capable of directly driving a 600 Ω isolation transformer. The output path includes
a mute function. The telecom codec also incorporates a loopback mode, in which codec output path and the input path
are connected in series.
TEL_SIDE_ENA
TEL_ATTATT TEL_GAIN
TINP
TINN
SIDETONE
SUPPRESSION
CIRCUIT
1bit ADC
DIGITAL
14
DECIMATION
FILTER
TEL_IN_ENA
TEL_OUT_ENA
TOUTP
TOUTN
4bit DAC
DIGITAL
14
NOISE
SHAPER
TEL_MUTE
Fig.7 Telecom codec block diagram.
The telecom sample rate (fst) is derived from the SIB interface clock pin (SIBCLK) and is programmable through the SIB
interface. The telecom sample rate is given by the following formula:
fst = (---6---4--(--2-×----×-T----FE----S-L--I-_-B---DC----LI--VK----[)-n----]--)
(15 < TEL_DIV[n] <128)
For example, a SIBCLK of 9.216 MHz, with a divisor of 40, results in a telecom sample rate of 7.2 kHz. Both the rising
and the falling edges of the SIBCLK are used in case TEL_DIV[n] is set to an odd number. In that case a 50% duty cycle
of the SIBCLK signal is mandatory to obtain time equidistant sampling.
The input path of the telecom codec has a programmable attenuationgain. It also implements a voice band filter, which
consists of an digital low pass filter, which is a part of the decimation filter. Therefore the pass band of the voice band
1999 Jul 20
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