Microchip Technology LE77D112BTC

Overview

LE77D112BTC from Zarlink Semiconductor is a dual-channel Voice over Subscriber Line Interface Circuit (VoSLIC™) designed for BORSCHT functions in voice-over-broadband systems. It delivers programmable DC feed (15–45 mA), 90 V_pk balanced ringing, and six software-configurable states-including Ringing, Line Test, and Reverse Polarity-using only +3.3 V and +8 to +40 V supplies in VoIP gateways and cable telephony NIUs.

For engineers reviewing the LE77D112BTC datasheet, LE77D112BTC pinout, LE77D112BTC application, or LE77D112BTC equivalent, this page provides verified device identity, confirmed dual-channel SLIC functionality, validated 44-pin eTQFP package mapping, exact state control logic (C3/C2/C1), and real-world fault detection behavior per GR-909.

Technical Context

The LE77D112BTC implements two independent buck-boost switching regulators that dynamically track Tip-Ring voltage to minimize power dissipation across all six operational states. Each channel uses dielectrically isolated bipolar technology and supports binary fault detection for hazardous potential, foreign EMF, resistive faults, and loop length via IMT/F pins.

Control is fully delegated to the companion LE78D11 VoSLAC™ device via MPI interface and three-state logic (C3/C2/C1), enabling full BORSCHT programmability-including two-wire AC impedance, dual current limit, metering, and ring trip thresholds-without external microcontroller intervention.

Key Specifications

Pinout & Package

LE77D112BTC is housed in a 44-pin enhanced Thin Quad Flat Package (eTQFP) with exposed thermal pad. Pin 1 is marked for orientation; BGND1/BGND2 and AGND provide separate analog/digital ground paths for noise isolation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LE77D112TC, the LE77D112BTC offers identical performance with mandatory RoHS compliance; versus Si32260-A-GM, it delivers lower system-level component count and built-in GR-909 diagnostics but requires companion LE78D11 for full BORSCHT control.

Availability

LE77D112BTC is available at Aetrix Electronics and suitable for VoIP gateways, cable telephony NIUs, and fiber-to-the-home terminals requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.

Supply support for LE77D112BTC 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.

The LE77D112BTC belongs to the VE770 Series VoSLIC™ product line, engineered specifically for cost-sensitive, high-density voice-over-broadband infrastructure requiring full BORSCHT functionality with minimal external components.

FAQ

What is the required companion device for LE77D112BTC?

The LE77D112BTC must be used with the LE78D11 VoSLAC™ device, which provides MPI interface control, signal generation, codec interfacing, and state management. The LE77D112BTC handles analog line interface functions only; all digital configuration, ringing waveform synthesis, and supervision logic reside in the LE78D11. Without the LE78D11, the LE77D112BTC cannot enter Ringing, Line Test, or programmable current limit states.

Does LE77D112BTC support 90 Vpk ringing with internal circuitry?

No, LE77D112BTC does not generate 90 V_pk internally. It requires an external PNP bipolar transistor (e.g., Zetex FZT955) driven by the SD1/SD2 pins, along with external filter components (CFL, CVREG, LVREG) and VSW ≥12 V. The LE77D112BTC's switching regulator controls the external transistor's base drive and tracks line voltage to maintain headroom, but the high-voltage ringing waveform is synthesized externally.

How is fault detection implemented on LE77D112BTC?

LE77D112BTC implements per-channel binary fault detection via F1 and F2 pins, which go low during longitudinal current faults (|IA−IB| > ILONG) or foreign voltage faults (e.g., VA above ground in Normal Active state). It supports GR-909-compliant drop tests for hazardous potential, foreign EMF, resistive faults, and loop length-all executed autonomously without host processor involvement. Fault status is latched until cleared by LE78D11 command.

What are the power supply requirements for LE77D112BTC?

LE77D112BTC requires two supplies: a +3.3 V DC logic supply (VCC) and a positive switching supply (VSW) ranging from +8 V to +40 V nominal. The VSW rail powers the internal buck-boost regulators and external PNP transistor for ringing. The wide VSW range allows flexible line powering schemes, including battery backup and PoE-derived sources, while the +3.3 V rail powers digital interfaces and bias circuits.

Can LE77D112BTC operate in standalone mode without LE78D11?

No, LE77D112BTC cannot operate standalone. Its C3/C2/C1 state control inputs, MPI interface dependencies, and clock-driven switching regulators require continuous coordination with the LE78D11 VoSLAC™ device. All six operational states-including Ringing, Line Test, and programmable current limits-are defined and triggered exclusively by LE78D11 commands. Without LE78D11, LE77D112BTC remains in reset or undefined state.