Microchip Technology LE79R79-1DJC

Overview

LE79R79-1DJC from Zarlink Semiconductor is a bipolar monolithic Ringing Subscriber Line Interface Circuit (R-SLIC) designed for short-loop telephony applications. It integrates on-chip trapezoidal ringing, programmable constant-current feed (IL = 21.7 mA typ), on-hook transmission, and dual battery switching (VBAT1: –40.5 to –75 V; VBAT2: –19 V to VBAT1), enabling compliance with LSSGR five-ringer equivalent specification in ISDN-TA and smart residential gateways.

For engineers reviewing the LE79R79-1DJC datasheet, LE79R79-1DJC pinout, LE79R79-1DJC application, or LE79R79-1DJC equivalent, key selection criteria include longitudinal balance (52 dB, polarity reversal enabled), 32-pin PLCC green RoHS-compliant package, integrated ring-trip and ground-key detection, and support for programmable open-circuit voltage via RSGH/RSGL.

Technical Context

The LE79R79-1DJC implements BORSHT functions-battery feed, overvoltage protection, ringing, supervision, hybrid, and test-with on-chip relay drivers (RYOUT1/RYOUT2), dual battery selection (B2EN-controlled), and current gain of 1000 at RSN node. Its two-wire impedance is set by a single external network, and transhybrid balance is achieved either via external components or companion QLSLAC™ codecs.

It features trapezoidal ringing generation using CMOS-compatible RINGIN input and external RC shaping, on-chip VEE regulator eliminating need for –5 V supply, and programmable loop-detect threshold with ±20% accuracy. The device operates across industrial temperature range (–40°C to +85°C) and supports ground-start signaling with VBAT1.

Key Specifications

Pinout & Package

LE79R79-1DJC is housed in a 32-pin PLCC (Plastic Leaded Chip Carrier) green RoHS-compliant package with exposed thermal pad not present (QFN variant has it). Pin 1 is marked for orientation; NC pins are unconnected internally.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LE79R79-2DJC, the LE79R79-1DJC trades 11 dB longitudinal balance for broader compatibility with cost-sensitive short-loop designs; versus LE79R70-1DJC, it delivers full BORSHT integration at the expense of higher complexity in non-ringing use cases.

Availability

LE79R79-1DJC is available at Aetrix Electronics and suitable for ISDN terminal adaptors, smart residential gateways, and network interface units requiring stable component supply, industrial-temperature operation, and RoHS-compliant packaging.

Supply support for LE79R79-1DJC 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 provider specializing in high-reliability analog and mixed-signal ICs for telecommunications infrastructure, later acquired by Microsemi (now Microchip). Known for SLIC, codec, and timing solutions.

The LE79R79 belongs to Zarlink's VE580 Series R-SLIC family, engineered specifically for cost-optimized, low-power short-loop CPE - targeting IADs, NIUs, and residential gateways where on-chip ringing and battery efficiency are critical.

FAQ

What is the primary function of the LE79R79-1DJC in a telephony system?

The LE79R79-1DJC serves as a Ringing Subscriber Line Interface Circuit (R-SLIC), providing full BORSHT functionality - battery feed, overvoltage protection, ringing, supervision, hybrid, and test - for analog telephone line interfaces. In the LE79R79-1DJC, on-chip trapezoidal ringing replaces external transformers, reducing system cost and size while maintaining LSSGR five-ringer compliance in short-loop deployments.

Does the LE79R79-1DJC support polarity reversal, and how is it enabled?

Yes, the LE79R79-1DJC supports polarity reversal as indicated by the "-1" suffix in its ordering code. This feature is implemented via internal circuitry controlled by the C3–C1 decoder inputs and is active only in Active or Standby states per the SLIC decoding table. Polarity reversal is essential for compatibility with certain legacy PBX systems and maintenance protocols requiring line-polarity switching.

How does the dual-battery architecture of the LE79R79-1DJC reduce power consumption?

The LE79R79-1DJC incorporates on-chip battery switching: during off-hook (active) operation, it draws from VBAT2 (–19 V to VBAT1) to minimize power dissipation; in on-hook (standby) state, it automatically switches to VBAT1 (–40.5 to –75 V) to meet open-circuit voltage requirements for fax machines and MTUs. This architecture cuts standby power by over 50% compared to single-battery SLICs, extending operational life in battery-backed CPE.

What external components are required to configure the LE79R79-1DJC for standard 600 Ω line impedance?

To program 600 Ω two-wire AC impedance, the LE79R79-1DJC requires an external impedance network connected to the RSN node, typically comprising RDC1 = 80 kΩ, RDC2 = 20 kΩ, RD = 75 kΩ, and CHP = 0.018 µF as specified in the reference design. These components set feed current, loop detect threshold, and AC termination - all referenced to the RSN summing node where current × 1000 equals metallic line current.

Can the LE79R79-1DJC be used in industrial temperature environments, and what validation supports this?

Yes, the LE79R79-1DJC is rated for –40°C to +85°C operation and validated per Bellcore GR-357-CORE Component Reliability Assurance Requirements. Electrical characterization and production testing were performed across this extended temperature range, ensuring guaranteed performance for transmission return loss (≥26 dB), longitudinal balance (52 dB), and supply current stability - making it suitable for outdoor NIUs, remote DSLAMs, and industrial gateways.