Datenblatt-Suchmaschine für elektronische Bauteile |
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CD22357A Datenblatt(PDF) 9 Page - Harris Corporation |
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CD22357A Datenblatt(HTML) 9 Page - Harris Corporation |
9 / 10 page 4-173 CD22354A, CD22357A A rising edge on the receive frame sync, FSR, will cause the PCM data at DR to be latched in on the next falling edge of the BCLKR. The remaining seven bits are latched on the succes- sive seven falling edges of the bit-clock (BCLKX in synchronous mode). Transmit Section The transmit section consists of a gain-adjustable input op- amp, an anti-aliasing filter, a low-pass filter, a high-pass filter and a compressing A/D converter. The input op-amp drives a RC active anti-aliasing filter. This filter eliminates the need for any off-chip filtering as it provides 30dB attenuation (Min) at the sampling frequency. From this filter the signal enters a 5th order low-pass filter clocked at 128kHz, followed by a 3rd order high- pass filter clock at 32kHz. The output of the high-pass filter directly drives the encoder capacitor ladder at an 8kHz sampling rate. A precision voltage reference is trimmed in manufacturing to provide an input overload of nominally 2.5VPEAK. Transmit frame sync pulse FSX controls the process. The 8-bit PCM data is clocked out at DX by the BCLKX. BCLKX can be varied from 64kHz to 2.048MHz. Receive Section The receive section consists of an expanding D/A converter and a low-pass filter which fulfills both the AT&T D3/D4 specifications and CCITT recommendations. PCM data enters the receive sec- tion at DR upon the occurrence of FSR, Receive Frame sync pulse. BCLKR, Receive Data Clock, which can range from 64kHz to 2.048MHz, clocks the 8-bit PCM data into the receive data reg- ister. A D/A conversion is performed on the 8-bit PCM data and the corresponding analog signal is held on the D/A capacitor lad- der. This signal is transferred to a switched capacitor low-pass fil- ter clocked at 128kHz to smooth the sample-and-hold signal as well as to compensate for the (SIN X)/X distortion. The filter is then followed by a second order Sallen and Key active filter capable of driving a 600 Ω load to a level of 7.2dBm. FIGURE 1. SHORT FRAME-SYNC TIMING 12345 6 78 MCLK R MCLK X BCLKX FSX tXDB tWWL tPM tFM tRM tWWH tSBFM tHOLD tHF tSF tDBD tDZC tDZC TS X 12345 678 12345 67 8 12345 678 BCLKR DX DR FSR tHOLD tHF tSF tSDB tHDB tHBD |
Ähnliche Teilenummer - CD22357A |
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Ähnliche Beschreibung - CD22357A |
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