Microchip MT9171ANR1: A Comprehensive Technical Overview
The Microchip MT9171ANR1 is a highly integrated, monolithic CMOS device designed to function as a complete Subscriber Line Interface Circuit (SLIC). This component is a cornerstone in telecommunications infrastructure, specifically engineered to provide the essential BORSHT functions (Battery feed, Overvoltage protection, Ringing, Supervision, Hybrid, and Testing) for a single telephone subscriber line. Its primary application is within central office switches, private branch exchanges (PBX), and key telephone systems, serving as the critical interface between a digital telephone switch and the analog two-wire local loop.
Architecture and Core Functionality
At its heart, the MT9171ANR1 is built to translate signals between the two-wire analog line and the four-wire digital path. The device incorporates a programmable balancing network, which is vital for effective hybrid functionality. This network cancels the transmitted signal from the received signal on the two-wire line, enabling full-duplex communication and significantly reducing echo. The programmability allows it to be matched to a wide range of line impedances, ensuring optimal performance across different regional telephony standards.
A key feature is its on-chip ringing relay and current sense drivers. This integration eliminates the need for external components to perform the high-voltage ringing function, simplifying board design, reducing the overall bill of materials (BOM), and enhancing system reliability. The device can generate various ringing patterns and is capable of detecting off-hook conditions even during the ringing cycle.
Key Technical Specifications and Features
Power Supply and Operation: The MT9171ANR1 operates from a single +5V power supply for its logic and control functions, while the high-voltage analog functions are powered from standard -48V or -24V battery supplies typical in telecommunication systems.
Data Conversion: It interfaces seamlessly with a PCM (Pulse Code Modulation) highway through its internal codec filter combo. It features a µ-law or A-law companding filter, compliant with the G.711 standard, and connects directly to a time-division multiplexed (TDM) serial bus at 2.048 Mbps (CEPT) or 1.544 Mbps (T1) rates.
Control and Programmability: The device is controlled via a microprocessor-friendly serial control interface. This allows for software configuration of all major parameters, including:
Transmit and receive gain levels.
Line impedance matching for the hybrid.
Ringing signal parameters.
Hook-status detection thresholds.
Protection: It boasts robust integrated overvoltage protection, safeguarding the sensitive internal circuitry and the connected switchboard from transient surges on the telephone line, such as those caused by lightning strikes or power line crosses.
Applications and System Integration
The MT9171ANR1 is designed for deployment in a multitude of telephony equipment. Its primary application is in the line card slots of digital central office (CO) switches. It is equally suited for modern IP-based systems, such as Voice over IP (VoIP) gateways and Integrated Access Devices (IADs), where it provides the legacy analog telephone interface. Its high level of integration makes it an ideal choice for compact and cost-sensitive designs, including smaller PBX systems and channel banks.
The Microchip MT9171ANR1 stands out as a robust, highly integrated, and flexible SLIC solution. Its combination of on-chip ringing support, a programmable hybrid, and comprehensive BORSHT functions consolidates numerous discrete components into a single package. This integration streamlines design, accelerates time-to-market, and enhances the reliability of telecommunication systems, solidifying its role as a fundamental building block in both legacy and modern voice network infrastructure.
Keywords:
Subscriber Line Interface Circuit (SLIC)
BORSHT
Programmable Balancing Network
On-Chip Ringing
PCM Highway
