Microchip Technology LE7920-2DJC

Overview

LE7920-2DJC from Zarlink Semiconductor is a Subscriber Line Interface Circuit (SLIC) designed for POTS line interface cards in telephony systems. It delivers active, ringing, standby, and disconnect control states; supports –19 V to –58 V battery operation; provides programmable constant-current feed and loop-detect threshold; and integrates four on-chip relay drivers-including one dedicated ringing driver-in a 32-pin PLCC package for low-cost, high-performance analog line card designs.

For engineers reviewing the LE7920-2DJC datasheet, LE7920-2DJC pinout, LE7920-2DJC application, or LE7920-2DJC equivalent, this page delivers verified technical context, exact pin functions, thermal management implementation details, relay driver specifications, and real-world telephony use cases-enabling accurate system integration, power budgeting, and compliance with Bellcore GR-357-CORE longitudinal balance requirements.

Technical Context

The LE7920-2DJC implements full two-wire metallic interface functionality using a current-gain architecture (500×) referenced to the RSN node, enabling precise DC feed current programming via external RDC network and two-wire AC impedance synthesis via VTX–RSN ZT network. Its on-chip thermal management (TMG) pin offloads power by connecting an external resistor to VBAT, reducing junction temperature during active and disconnect states.

Control logic uses TTL-compatible C2/C1 inputs to select among four operational states (Active, Ringing, Standby, Disconnect), while D1–D3 inputs independently drive three general-purpose open-collector relay outputs (RYOUT1–3) and RINGOUT-each rated for 50 mA sink current and featuring internal BGND-emitter connection and 6–7.2 V zener clamping.

Key Specifications

Pinout & Package

LE7920-2DJC is housed in a 32-pin Plastic Leaded Chip Carrier (PLCC) package per JEDEC MS-016, with dimensions 0.490" × 0.590" × 0.132" (nominal), gull-wing leads, and pin 1 orientation marked. The package is RoHS-compliant green (lead-free matte-tin plating), rated for peak reflow up to 245°C.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar subscriber line interface applications.

Compared with LE7920-2DJC, LE7920-1DJC offers identical functionality at reduced longitudinal performance, while Si32176 replaces discrete SLIC+codec+power with a system-on-chip-but demands PCB redesign, firmware adaptation, and forfeits the TMG-based thermal headroom critical for high-temperature deployments.

Availability

LE7920-2DJC is available at Aetrix Electronics and suitable for central office line cards, digital loop carrier terminals, VoIP gateway FXS ports, and emergency services line interfaces requiring stable component supply, long-term lifecycle support, and RoHS-compliant green packaging.

Supply support for LE7920-2DJC 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 semiconductor company specializing in voice, timing, and broadband communications ICs, acquired by Microsemi in 2011 and later integrated into Microchip Technology.

The LE7920-2DJC belongs to Zarlink's VE580 Series SLIC product line, engineered specifically for cost-sensitive, high-reliability POTS line interface applications in telecom infrastructure equipment meeting Bellcore GR-357-CORE requirements.

FAQ

What is the function of the TMG pin on the LE7920-2DJC?

The TMG pin on the LE7920-2DJC connects to an external resistor (RTMG) tied to VBAT to divert power away from the die during active and disconnect states. This thermal management feature reduces junction temperature-critical for maintaining reliability at 70°C ambient and enabling continuous 1.7 W dissipation in the 32-pin PLCC package without a heatsink. Designers calculate RTMG using the formula RTMG ≥ (VBAT − 6 V)/ILOOP − 70 Ω.

How does the LE7920-2DJC achieve 63 dB longitudinal balance?

The LE7920-2DJC achieves 63 dB longitudinal balance (L-T and L-4) through matched internal circuitry and precision layout in the –2 performance grade variant. This specification is guaranteed over 0°C to +70°C and validated per Bellcore GR-357-CORE test methods using Test Circuit C. The balance is maintained across 200 Hz–3.4 kHz and enables compliance in central office line cards where common-mode noise rejection is mandatory.

Can the LE7920-2DJC operate without a –5 V supply?

Yes, the LE7920-2DJC operates without a –5 V supply. It requires only a +5 V VCC rail and a negative battery supply (VBAT from –19 V to –58 V). All internal biasing, amplifiers, and relay drivers are designed to function within this dual-rail configuration-eliminating the need for a third power rail and simplifying power supply design in line card applications.

What is the purpose of the RSN pin on the LE7920-2DJC?

The RSN (Receive Summing Node) pin on the LE7920-2DJC serves as the reference point for the device's 500× current gain architecture. The metallic current between A(TIP) and B(RING) equals 500 times the current injected into RSN. All key networks-including DC feed (RDC), two-wire impedance (ZT), and receive gain (ZRX)-connect directly to RSN, making it the central analog node for configuring line interface behavior.

How many relay drivers does the LE7920-2DJC integrate, and what are their ratings?

The LE7920-2DJC integrates four on-chip relay drivers: one dedicated RINGOUT and three general-purpose RYOUT1–3 outputs. All are open-collector with emitters tied internally to BGND, rated for 50 mA continuous sink current, 0.7 V maximum on-voltage at 40 mA, and 7.2 V zener breakover for transient protection-enabling direct drive of standard telecom relays without external components.