Microchip Technology LE9551DMQC

Overview

LE9551DMQC 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, GR909 test compliance, and serial interface control with reset. Used in voice loop battery feed, ringing, and supervision for cable-based VoIP access systems.

For engineers reviewing the LE9551DMQC datasheet, LE9551DMQC pinout, LE9551DMQC application, or LE9551DMQC equivalent, key selection criteria include its 28-pin 4×5 mm QFN package, –145 V ringing capability, DC loop closure/ring trip detection, thermal shutdown with hysteresis, and integrated test load switch for algorithmic diagnostics.

Technical Context

The LE9551DMQC implements a high-voltage analog front-end for voice line interface with dedicated transmit/receive gain paths (G_TX = 150, G_RX = 13.67), longitudinal-to-metallic balance ≥52 dB, and PSRR ≥40 dB over 500 Hz–3 kHz. Its serial interface supports DIN/CLK/DOUT/EN/RESET signaling for configuration and status reporting.

It integrates DC feed control (DCF), ring trip fault detection (RTFLT), dual-threshold loop start/ring-ground sensing, and a test load switch (TLD) enabling GR909-compliant diagnostics. The device operates across –145 V ringing battery (D-grade) and draws ≤359 mW in ring state at no load.

Key Specifications

Pinout & Package

LE9551DMQC uses a green RoHS-compliant 4×5 mm, 28-pin QFN package 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 LE9551CMQC, LE9551DMQC delivers higher ringing voltage headroom critical for North American PSTN compatibility; versus LE9541DUQC, it reduces package size and power consumption while sacrificing channel scalability.

Availability

LE9551DMQC is available at Aetrix Electronics and suitable for VoIP residential gateways, cable modem telephony adapters (eMTA), and small-office VoIP terminals requiring stable component supply and long-term lifecycle support.

Supply support for LE9551DMQC 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 analog and mixed-signal ICs for aerospace, defense, communications, and industrial markets.

The LE9551DMQC belongs to the VE950 Series SLIC family, engineered specifically for broadband voice access equipment interfacing with Broadcom SoCs in short-loop cable and DSL environments.

FAQ

What is the maximum ringing battery voltage supported by LE9551DMQC?

The LE9551DMQC supports up to –145 V ringing battery voltage, as specified in Microsemi Product Brief #153225 (v2). This D-grade rating meets North American PSTN requirements and distinguishes it from the C-grade LE9551CMQC (–100 V). The –145 V capability is confirmed in electrical specifications under "Ring state, no load, VBAT = –145 V (Le9541/51D)" with power consumption of 312–359 mW.

Does LE9551DMQC require an external crystal or clock source?

No, the LE9551DMQC does not require an external crystal or clock source. It operates using the host SoC's serial interface clock (CLK pin) for synchronization and derives internal timing from that signal. The device contains no on-chip oscillator or PLL requiring external frequency control; all timing-critical functions-including ringing waveform generation and test algorithms-are controlled via the serial interface and internal analog circuitry.

How does LE9551DMQC implement GR909 compliance?

The LE9551DMQC implements GR909 compliance through its integrated test load switch (TLD pin) and associated fault reporting (RTFLT, ITR). When activated, TLD connects a known internal load to simulate line conditions for impedance measurement, loopback, and fault injection-core requirements of Telcordia GR-909. Status is reported via serial interface, enabling host SoC to execute automated line tests without external components.

What is the function of the RTFLT pin on LE9551DMQC?

The RTFLT pin on LE9551DMQC is an open-drain output that asserts low when a ring trip condition is detected. It uses dual-threshold comparators to distinguish between valid ring signals and transient noise, ensuring reliable off-hook detection. RTFLT status is also accessible via the serial interface register map, allowing software polling or interrupt-driven handling. This pin directly interfaces with host SoC GPIO or interrupt controllers in Broadcom BCM338x/BCM339x reference designs.

Is LE9551DMQC pin-compatible with LE9541DUQC?

No, LE9551DMQC is not pin-compatible with LE9541DUQC. LE9551DMQC uses a 28-pin 4×5 mm QFN package (Figure 2), while LE9541DUQC uses a 40-pin 6×6 mm QFN (Figure 1). Though functionally equivalent per channel, their pin counts, layouts, and thermal pad dimensions differ. Migration requires PCB redesign; however, both share identical serial interface protocol and register mapping for software compatibility.