No Companding Required
The voiceband codec provides a CCITT G.711/712-compliant voice interface without companding. The OakDSPCore performs vocoder operations for QCELP-13 and QCELP-8 for North America, as well as EVRC for Asian markets. The codec uses SC second-order Δ−Σ front ends with a 2.6-MHz oversampling rate. The voice ADC path's decimated output is fed into a bandpass filter. This filter offers precise, in-band spectral shaping to eliminate signal energies below 300 Hz and above 3.6 kHz for proper speech compression.
After bandpass filtering and modulation in the voice DAC path, the bitstream data is converted into an analog signal using a 1-bit DAC. This is followed by a first-order SCF and a class A-B reconstruction filter that drives 600-Ω speakers.
While this describes the main signal paths, other features on board haven't been mentioned. These include auxiliary DACs, a real-time clock, on-chip RAM for the ARM7, two serial I/O channels, a keypad interface, an external-memory path, and interfaces for the display, speaker, and microphone . In fact, all that needs to be added for a complete solution is external and flash memory, the RF/IF stages, channel-isolation filters, and the RF low-noise and power amplifiers.
Keeping with the original goals of maximum flexibility, the CBP 3.0 leverages LSI's CoreWare design methodology and library of building blocks to help the customer achieve maximum product differentiation while minimizing time-to-market. Potential value-added functionality includes an infrared interface, a custom display interface, a USB interface, PDA functions, and hands-free voice recognition in the DSP or control processor. The device also is WAP-enabled and supports trimode operation.
The core operates off 1.8 V, while the mixed-signal circuitry operates down to 3.0 V. The device comes in a 16- by 16-mm CSP with a 1-mm profile and a 0.8-mm ball pitch.
A slew of software deliverables are provided with the chip. These include the DSP operating system, hardware drivers, vocoders and algorithms, and an IS-95B protocol stack from Isotel Inc. that includes source code. LSI Logic also makes available its ETS diagnostic software, its Graphical Analysis Tool, and third-party Design Verification Tool software.
Price & Availability
Pricing for the CBP 3.0, which is shipping now, is $35 each per 10,000 units.
LSI Logic Inc., 1551 McCarthy Blvd., Milpitas, CA 95035; Greg Helton, (408) 433-8000; ghelton@lsil.com; www.lsilogic.com.