Microchip Technology LE9551CMQCT

Overview

LE9551CMQCT from Microsemi is a single-channel high-voltage ringing SLIC optimized for short-loop residential gateways interfacing with Broadcom BCM338x/BCM339x SoCs. It delivers –100 V ringing battery support, 7-kHz wide-band operation, serial interface control with reset, and integrated loop supervision including ring trip, loop start, and thermal shutdown with hysteresis.

For engineers reviewing the LE9551CMQCT datasheet, LE9551CMQCT pinout, LE9551CMQCT application, or LE9551CMQCT equivalent, key selection considerations include its 4×5 mm 28-pin QFN package, GR909 test compliance, DC feed + ringing + supervision integration, and compatibility with voice-over-cable infrastructure requiring metallic balance ≥52 dB and PSRR ≥40 dB.

Technical Context

The LE9551CMQCT implements a fully integrated subscriber line interface circuit with dedicated DC feed, high-bandwidth ringing generation (up to –100 V), and analog signal path gain control (TX gain = 150, RX gain = 13.67). Its serial interface supports configuration, status reporting, and reset-enabling tight coupling with Broadcom SoCs in cable gateway designs.

It features dual-threshold detection for loop start, ring trip, and ring-ground events, plus thermal shutdown with hysteresis and a test load switch for embedded GR909 algorithm execution. The device operates across active, power-scan, and ring states with verified power consumption at –60 V and –100 V battery conditions.

Key Specifications

Pinout & Package

LE9551CMQCT uses a green RoHS-compliant 28-pin QFN package (4 mm × 5 mm, 0.5 mm pitch) with exposed thermal pad. Pin assignment follows Figure 2 of Microsemi Product Brief #153225 (v2, Feb 2016).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LE9551DMQCT, LE9551CMQCT reduces thermal load and BOM cost for standard –100 V applications; compared with LE9541CUQC, it cuts PCB area and component count for dedicated single-channel deployments without sacrificing core SLIC functionality.

Availability

LE9551CMQCT is available at Aetrix Electronics and suitable for residential gateways, VoIP terminal adapters, small-office PBX interfaces, and remote PHY node voice ports requiring stable component supply and long-term manufacturability.

Supply support for LE9551CMQCT 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

Microsemi Corporation (now part of Microchip Technology) designs high-reliability semiconductor solutions for aerospace, defense, communications, and industrial markets, with expertise in timing, power management, and analog interface ICs.

The LE9551CMQCT belongs to the VE950 Series SLIC product line, engineered specifically for broadband voice-over-cable infrastructure requiring integrated ringing, feed, and supervision in compact form factors.

FAQ

What is the maximum ringing voltage supported by the LE9551CMQCT?

The LE9551CMQCT supports up to –100 V ringing battery voltage, as specified for the "C" variant in Microsemi's Product Brief #153225. This rating is validated for no-load ring state operation and defines the upper limit for safe, compliant ringing signal generation in residential cable gateway applications. Exceeding this voltage may compromise reliability or violate GR909 test limits. Always verify line transformer ratings and protection network design when using LE9551CMQCT in production.

Is the LE9551CMQCT pin-compatible with the LE9541 series?

No, the LE9551CMQCT is not pin-compatible with the LE9541 series. It uses a 28-pin 4×5 mm QFN package, whereas LE9541 devices use a 40-pin 6×6 mm QFN. Pin assignments differ significantly-e.g., LE9551CMQCT has dedicated RTFLT and TLD pins not present in the same locations on LE9541. Board redesign is required for migration. LE9551CMQCT is functionally equivalent to one channel of LE9540 but physically distinct.

Does the LE9551CMQCT support GR909 compliance testing?

Yes, the LE9551CMQCT explicitly supports GR909 testing per Microsemi documentation. Its 7-kHz wide-band operation, ≥52 dB longitudinal balance, and integrated test load switch (TLD) enable execution of GR909-defined algorithms-including wide-band frequency response, echo return loss, and noise measurements-without external instrumentation. This capability is confirmed in the Product Brief and referenced in the "Features" section of the official datasheet.

What serial interface protocol does the LE9551CMQCT use?

The LE9551CMQCT uses a 4-wire synchronous serial interface compatible with SPI protocols, featuring DIN (data in), DOUT (data out), CLK (clock), and EN (enable) signals. It also includes a dedicated RESET pin for hardware initialization. Communication supports register read/write for configuration, real-time status reporting (e.g., RTFLT fault flag), and control of functions like DC feed enable (DCF) and test load activation (TLD), all documented in the LE9551 register map.

How does thermal management work in the LE9551CMQCT?

The LE9551CMQCT incorporates thermal shutdown with hysteresis: it disables output stages when die temperature exceeds ~150 °C and remains off until temperature falls below ~135 °C. This behavior is confirmed in the "Features" list and electrical specifications table. The 4×5 mm QFN package includes an exposed thermal pad that must be soldered to a PCB copper pour for effective heat dissipation-critical given its 236 mW max ring-state power dissipation at –100 V.