Analog Front-End Brings Optical Isolation to Powerline Modems

Dec. 3, 2003
Aiming to make a dent in the emerging narrowband powerline communication modems used in automated meter readings (AMRs) and home-appliance automation
Aiming to make a dent in the emerging narrowband powerline communication modems used in automated meter readings (AMRs) and home-appliance automation applications, Agilent Technologies has extended its optoelectronics expertise and manufacturing muscle to the front-end section of these modems. The result is a fully integrated, optical-based analog front-end (AFE) chip for narrowband powerline modems (PLMs). This 0.6 micron biCMOS-based data access arrangement (DAA) chip, labeled HCPL-800J, replaces more than 30 discrete components, while reducing board space by 50%. Furthermore, the developer claims that it is the first fully integrated optical-based AFE chip for powerline modems. The single-chip solution improves PLM performance and reliability, and simplifies design. By combining isolation, Tx line driver and Rx amplifiers functions in a single package, it provides a lower cost, higher performance alternative to current AFE designs that combine an isolation transformer with multiple discrete components.

In addition to eliminating signal transformer and drastically cutting parts count, the DAA chip provides high isolation and very low Tx harmonic distortion to comply with safety and EMI standards. At 4.2-kV isolation and -60-dB Tx harmonic distortion, the HCPL-800J chip is crafted to comply with international safety standards such as UL, CSA and VDE, as well as EMI specifications such as CENELEC EN-50065-1, FCC part 15 Class B. However, approval under the following safety standards is currently pending: VDE0884/06.92 (IEC/EN/DIN EN60747-5-2) with VIORM = 891-V peak; UL 1577, component recognition program, File E55361; and CSA Acceptance Notice #5, File CA 88324.

"Excellent transmitter performance is achieved with the use of a high-efficiency, low-distortion line driver stage on-chip," said Simon Lam, product manager for Agilent's Isolation Products Division based in Singapore. He added that transmitter robustness is further enhanced with integrated load detection and overtemperature protection functions. The HCPL-800J is designed to work with various transceiver ICs and significantly simplifies the implementation of a powerline modem.

The AFE chip offers 1-A (p-p) output drive current capability. Typical input referred noise spec is rated at 25-nV/√Hz. Other features include overtemperature shutdown, line status monitoring (load detection and low supply voltage detection), undervoltage detection, and a wide operating temperature range.

The HCPL-800J incorporates two integrated circuits: a control IC and a line IC, optically isolated from each other. The modulated signal from the PLM transceiver is input to the control IC. This transmit signal is optically coupled to the line IC, then amplified and sent to the powerline. In the other direction, a potentially weak and noisy signal from the powerline is received by the line IC and optically coupled to the control IC, where it is amplified and output to the PLM transceiver. However, to complete the AFE solution, it requires a simple LC coupling circuit and filters. Narrowband powerline communication systems typically operate at up to 9.6 kb/s and use PLMs that plug in to the ac power outlet to deliver control and automation functions.

Designed for powerline modems operating at frequencies up to 450 kHz, the HCPL-800J requires two 5-V power supplies and comes in a 16-pin SOIC package. It is priced at less than $2.80 each in high-volume quantities. It is slated to go into full production in the first quarter of 2004. An evaluation board also is available. In addition, the company is developing a reference design scheduled for release in the first quarter next year. Other variations are in the works to address custom, as well as price-sensitive applications. Moreover, Agilent is planning to extend its capability to broadband powerline modems.

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