Microchip Technology LE87251NQC

Overview

LE87251NQC from Zarlink Semiconductor is a dual-channel, high-voltage differential line driver IC designed for full-rate ADSL2+ and HDSL systems. It delivers 450 mA peak output drive, fixed 13× voltage gain, ±5 V to ±12 V dual-supply operation (or 10–24 V single supply), and −75 dBc THD at 1 MHz into 60 Ω - enabling robust DSL line interface with low power dissipation in carrier-class access equipment.

For engineers reviewing the LE87251NQC datasheet, LE87251NQC pinout, LE87251NQC application, or LE87251NQC equivalent, this page provides verified technical context, validated pin functions, confirmed dual-channel ADSL2+ line driving specifications, RoHS-compliant QFN-16 package details, and real-world alternative selection guidance - all grounded in the official June 2009 Zarlink datasheet (Doc #129739).

Technical Context

The LE87251NQC integrates two independent pairs of wideband amplifiers (A/B and C/D) fabricated in Zarlink's HV30 Bipolar SOI process, enabling low-power operation while maintaining high output swing (±11.1 V into 100 Ω) and excellent linearity. Each channel features internal fixed-gain architecture eliminating external feedback resistors and reducing component count.

Channel enable/disable is controlled via dedicated ENAB (for amplifiers A/B) and ENCD (for amplifiers C/D) pins, each internally pulled up to 2.5 V via 50 kΩ on-chip resistors. The device supports both dual-rail (±12 V) and single-rail (24 V) configurations, with GND referenced to VS− in single-supply mode - critical for flexible system-level power architecture design.

Key Specifications

Pinout & Package

LE87251NQC uses a thermally enhanced 16-pin QFN package (4 mm × 4 mm) with an exposed die pad on the underside for heat dissipation. The pad must be soldered to a PCB copper plane connected via multiple thermal vias to internal ground or power planes per Zarlink layout guidelines.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-channel DSL line driver applications.

Compared with LE87251NQC, MAX22026ETJ+ offers lower integration and narrower supply range but suits compact VDSL2 modems, while AD8016ARUZ provides higher bandwidth but lacks ADSL2+ linearity certification and dual-channel efficiency - making LE87251NQC the only option meeting full-rate ADSL2+ line card requirements with dual-channel, low-power, and RoHS-compliant operation.

Availability

LE87251NQC is available at Aetrix Electronics and suitable for ADSL2+ line cards, HDSL transceivers, multi-port xDSL gateways, and DSL test equipment requiring stable component supply, long-lifecycle support, and RoHS-compliant green packaging.

Supply support for LE87251NQC 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 Inc. was a Canadian fabless semiconductor company specializing in communications ICs, acquired by Microsemi in 2011 and later integrated into Microchip Technology. It pioneered high-performance DSL analog front-end solutions.

The LE87251NQC belongs to Zarlink's BD870 Series of ADSL2+ line drivers, engineered specifically for carrier-grade DSLAMs and CPE requiring high-output swing, ultra-low distortion, and dual-channel integration in minimal footprint.

FAQ

What is the maximum differential output voltage of the LE87251NQC into a 100 Ω load?

The LE87251NQC delivers 44 V_p-p differential output into a 100 Ω load, as specified in the June 2009 Zarlink datasheet (Document #129739). This value is measured under standard ±12 V supply conditions and confirms its suitability for full-rate ADSL2+ line driving where high voltage swing is required to overcome line attenuation. The LE87251NQC achieves this while maintaining −75 dBc THD at 1 MHz, ensuring spectral compliance.

Does the LE87251NQC support single-supply operation, and what is the valid voltage range?

Yes, the LE87251NQC supports single-supply operation with VS+ connected to a positive rail (10 V to 24 V) and VS− tied to GND. Per the datasheet, it operates correctly at +24 V ±5% in this configuration, enabling simplified power design in cost-sensitive CPE. The LE87251NQC maintains full functionality including ENAB/ENCD control and 13× gain accuracy under single-supply conditions.

How does the LE87251NQC handle thermal management, and what PCB layout is required?

The LE87251NQC uses a 16-pin QFN package with an exposed thermal pad that must be soldered to a PCB copper plane connected via ≥4 thermal vias to internal ground/power layers. Zarlink specifies this layout to maintain junction temperature ≤150°C under full-load operation. Failure to implement proper thermal vias results in derated output current and potential reliability issues - a requirement explicitly defined in the LE87251NQC datasheet Section 3.1.

What is the function of the VCMAB and VCMCD pins on the LE87251NQC?

VCMAB sets the common-mode bias voltage for amplifiers A and B (Channel 1), while VCMCD sets it for amplifiers C and D (Channel 2). These pins determine the DC level around which differential outputs swing and must be driven externally - typically from a precision voltage divider or DAC. In the LE87251NQC, they are not internally tied, allowing independent common-mode control per channel for advanced line balancing.

Is the LE87251NQC pin-compatible with other devices in the BD870 Series, such as LE87250?

No, the LE87251NQC is not pin-compatible with LE87250. While both belong to the BD870 Series, LE87250 is a single-channel variant with different pin assignment (e.g., only one ENx pin, fewer VOUT/VIN terminals). The LE87251NQC's 16-pin QFN layout is unique to its dual-channel architecture - confirmed by the official pin diagram in the LE87251NQC datasheet (Figure 1, Page 3). PCB redesign is required for substitution.