Microchip Technology LE9551DMQCT

Overview

LE9551DMQCT from Microsemi is a single-channel high-voltage ringing SLIC optimized for short-loop residential gateways interfacing with Broadcom BCM338x/BCM339x SoCs. It delivers –145 V ringing battery support, 7-kHz wide-band operation, and serial interface control with reset. Used in voice loop battery feed, ringing, and supervision for cable-based VoIP gateways.

For engineers reviewing the LE9551DMQCT datasheet, LE9551DMQCT pinout, LE9551DMQCT application, or LE9551DMQCT equivalent, key selection criteria include its 28-pin 4×5 mm QFN package, –145 V ringing capability, GR909 test compliance, thermal shutdown with hysteresis, and functional equivalence to channel 1 of LE9540.

Technical Context

The LE9551DMQCT implements a high-voltage analog front-end for voice line interface, integrating DC feed, ringing generation, and loop supervision functions. Its architecture supports dual-threshold loop start/ring trip detection, test load switching for integrated diagnostics, and longitudinal-to-metallic balance of 52 dB.

Control and status reporting occur via a synchronous serial interface (DIN/CLK/DOUT/EN/RESET) operating at VDD = 3.3 V. The device features PSRR ≥40 dB over 500 Hz–3 kHz in active modes and maintains ±0.05 dB gain flatness across 300 Hz–6.4 kHz with 600 Ω termination.

Key Specifications

Pinout & Package

LE9551DMQCT is housed in a green, RoHS-compliant 4×5 mm, 28-pin QFN package with exposed thermal pad. Pin assignment follows Figure 2 of Microsemi Product Brief Document ID# 153225 (v2, Feb 2016).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LE9551CMQCT, LE9551DMQCT offers identical performance in tape-and-reel format for automated SMT production; compared with LE9541DUQCT, it trades dual-channel flexibility for 30% smaller footprint and lower component cost in single-line deployments.

Availability

LE9551DMQCT is available at Aetrix Electronics and suitable for voice-over-cable gateways, residential VoIP terminals, and GR909-compliant test platforms requiring stable component supply and long-term manufacturability.

Supply support for LE9551DMQCT 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) is a U.S.-based semiconductor company specializing in high-reliability analog, mixed-signal, and RF solutions for aerospace, defense, communications, and industrial markets.

The LE9551DMQCT belongs to the VE950 Series SLIC product line, designed specifically for cost-optimized, single-channel voice line interface in broadband residential gateways interfacing with Broadcom SoCs.

FAQ

What is the maximum ringing battery voltage supported by the LE9551DMQCT?

The LE9551DMQCT supports up to –145 V ringing battery voltage, as specified for the "D" variant in Microsemi's Product Brief (Document ID# 153225). This rating enables reliable operation in long-loop residential voice applications and satisfies GR909 wideband ringing requirements. The LE9551DMQCT achieves this using internal high-voltage design elements and is distinct from the –100 V "C" variant. Always verify VBAT derating versus ambient temperature in final design.

Is the LE9551DMQCT pin-compatible with the LE9541 series?

No, the LE9551DMQCT 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. Although both share functional equivalence to channel 1 of LE9540, their pin assignments differ significantly - confirmed by Figures 1 and 2 in Microsemi's Product Brief. Board redesign is required when migrating between LE9551DMQCT and LE9541DUQCT.

Does the LE9551DMQCT support GR909 testing?

Yes, the LE9551DMQCT explicitly supports GR909 testing, as stated in Microsemi's official documentation. Its 7-kHz wide-band design, dual-threshold loop detection, and integrated test load switch (TLD) enable automated compliance verification per Telcordia GR909 Section 4.3. The LE9551DMQCT's gain flatness (±0.05 dB from 300 Hz–6.4 kHz) and longitudinal balance (52 dB) further ensure measurement accuracy during GR909 validation.

What is the function of the TLD pin on the LE9551DMQCT?

The TLD (Test Load Switch) pin on the LE9551DMQCT controls an internal MOSFET that connects a calibrated test load between tip and ring. When asserted via serial command, it enables automated GR909 loop impedance measurements without external relays or switches. This feature is integral to the LE9551DMQCT's self-test capability and reduces test fixture complexity. The TLD function is documented in the Block Diagram and Pin Assignment sections of Microsemi's Product Brief.

What supply voltages does the LE9551DMQCT require?

The LE9551DMQCT requires three primary supplies: VDD (digital core, 3.3 V), VCC (I/O and interface, 3.3 V), and VBAT (high-voltage battery, –145 V max). VREF and IREF provide internal bias references; VITR and RCVP set current sense thresholds. All analog supplies derive from VBAT and local regulation - no external high-voltage regulators are needed. Decoupling capacitors (e.g., 0.1 µF CVBAT, CVCC) are mandatory per the Reference Schematic in Microsemi's Product Brief.