Microchip Technology LE57D122BTC

Overview

LE57D122BTC from Zarlink Semiconductor is a dual-channel Subscriber Line Interface Circuit (SLIC) in 44-pin eTQFP package, supporting loop start and ground start telephony interfaces with –63 dB reverse polarity performance, programmable current limit, on-chip thermal management, and 2.0 Vrms metering capability for POTS line cards in India, China, Korea, Japan, Taiwan, Australia, and North America DLC applications.

For engineers reviewing the LE57D122BTC datasheet, LE57D122BTC pinout, LE57D122BTC application, or LE57D122BTC equivalent, this page delivers verified specifications, dual-channel supervision states (Active, Active Metering, Standby, Tip Open, Disconnect), battery voltage range (–39 to –60 V), per-channel fault detection, and thermal shutdown protection - all critical for high-density telecom line card design and compliance with TR-57-CORE, GF002, G/LLT, and ITU Q.552 requirements.

Technical Context

The LE57D122BTC integrates two fully independent SLIC channels into a single 44-pin eTQFP package, each with programmable off-hook/ground-start thresholds (via RD resistor), ring-trip detection (DBi/DAC inputs), and per-channel thermal shutdown (>145°C junction, 10°C hysteresis). It supports seven discrete operating states decoded via C1i/C2i/C3i control pins, including Active Metering and Reverse Polarity Metering for 2.0 Vrms pulse metering.

Its power feed controller uses CAS-filtered bias and CDCi-based DC feed filtering to regulate loop current (22–33 mA nominal range) across 2000 Ω loads at –48 V, while TMG1/TMG2 outputs enable external thermal management resistors to offload power dissipation - reducing worst-case SLIC channel power to <1.6 W with both channels active.

Key Specifications

Pinout & Package

LE57D122BTC is housed in a thermally enhanced 44-pin eTQFP (12 × 12 mm) package with exposed thermal pad connected to VBAT. The package supports high-density line card layouts and requires soldering of the EPAD to PCB for optimal thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel SLIC applications.

Compared with LE57D121BTC and LE5711, the LE57D122BTC provides superior reverse polarity rejection (–63 dB), integrated thermal management for lower power dissipation, and dedicated metering states - making it the only choice for new designs targeting India, China, and GF002-compliant pulse metering applications.

Availability

LE57D122BTC is available at Aetrix Electronics and suitable for Central Office line cards, DLC remote terminals, pulse metering gateways, and industrial telecom gateways requiring stable component supply, long-term lifecycle support, and RoHS-compliant green packaging.

Supply support for LE57D122BTC includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Zarlink Semiconductor was a fabless semiconductor company specializing in communications ICs, acquired by Microsemi in 2011 and later integrated into Microchip Technology. It pioneered high-performance SLIC and SLAC solutions for telecom infrastructure.

The LE57D122BTC belongs to the VE580 Series dual SLIC product line, designed specifically for high-density, low-power POTS line cards requiring global regulatory compliance, programmable supervision, and integrated thermal management in compact eTQFP packages.

FAQ

What is the reverse polarity attenuation specification for LE57D122BTC?

The LE57D122BTC is specified for –63 dB reverse polarity attenuation, as confirmed in the Ordering Information section of the datasheet. This value distinguishes it from the LE57D121BTC (–53 dB) and is essential for meeting GF002 and G/LLT earth-backed ringing requirements in India and China. The attenuation is measured under standard test conditions with VCC = 5 V, BAT = –52 V, and RL = 600 Ω.

Does LE57D122BTC support pulse metering applications?

Yes, the LE57D122BTC explicitly supports 2.0 Vrms pulse metering in Active Metering and Reverse Polarity Metering states. Its design enables direct interface with Zarlink QLSLAC codecs (e.g., LE58QL02, LE58083) to meet ITU Q.552 requirements for 12/16 kHz metering in Indian and Chinese markets. The datasheet confirms 2.0 Vrms into 200 Ω capability with appropriate external network configuration.

What are the thermal management capabilities of LE57D122BTC?

The LE57D122BTC features per-channel TMG1 and TMG2 outputs that connect to VBAT via external resistors (RTMG) to offload power during off-hook operation. With proper RTMG selection (e.g., 1.8 kΩ, 5%), total worst-case SLIC power dissipation remains below 1.6 W with both channels active - significantly reducing die temperature versus non-TMG SLICs. The exposed thermal pad must be soldered to PCB and connected to VBAT for full benefit.

How does LE57D122BTC handle fault detection and thermal shutdown?

The LE57D122BTC provides independent FLT1/FLT2 outputs that go low upon longitudinal overvoltage detection on tip/ring, and per-channel thermal shutdown triggers above 145°C junction temperature (with ~10°C hysteresis). Critically, thermal shutdown on one channel does not affect the other - ensuring continued operation of the healthy channel. Both FLT and DET pins are logic-compatible and can be monitored directly by host microcontrollers.

What is the recommended battery voltage range for LE57D122BTC operation?

The LE57D122BTC is rated for battery supply (VBAT) between –39 V and –60 V, as specified in the Operating Ranges table. This range covers standard central office (–48 V) and DLC battery systems globally. Operation outside this range risks permanent damage; absolute maximum rating is –63 V. The device draws <24 mW per channel in standby and regulates loop current across 2000 Ω loads at –48 V.