Microchip Technology LE57D111BTCT

Overview

LE57D111BTCT from Zarlink Semiconductor is a dual-channel Subscriber Line Interface Circuit (SLIC) designed for high-density POTS linecards, delivering –39 to –58 V battery operation, on-chip thermal management (TMG), and programmable ring-trip detection. It integrates two SLIC channels into a single 44-pin eTQFP package, supports Active/Reverse Polarity/Standby/Disconnect states, and enables low-standby-power, China-compliant (GF002-9002.1) telephony systems.

For engineers reviewing the LE57D111BTCT datasheet, LE57D111BTCT pinout, LE57D111BTCT application, or LE57D111BTCT equivalent, this page provides verified technical context, confirmed pin functions, real-world linecard design implications, and validated alternative options for CO/DLC deployments requiring dual-channel loop feed, off-hook supervision, and thermal-aware power delivery.

Technical Context

The LE57D111BTCT implements two independent SLIC channels sharing a single +5 V (VCC) and negative battery (VBAT) supply, with separate TIP/RING outputs, RSN summing nodes, and TMG thermal management terminals per channel. Each channel features TTL-compatible state decoding (C1i/C2i), dual-mode loop detection (off-hook threshold 9–11 mA active, 4–6 mA standby), and programmable DC feed current via IREF resistor.

Its signal path includes metallic AC voltage sensing at A/B pins, scaled transmit output (VTX) with 20 Ω impedance, longitudinal feedback for noise rejection (>50 dB L-T balance), and integrated ring-trip comparators using DAC as common reference and DBi as channel-specific positive input - enabling precise ring-trip detection during Disconnect state.

Key Specifications

Pinout & Package

The LE57D111BTCT is housed in a 44-pin enhanced Thin Quad Flat Package (eTQFP) with exposed thermal pad tied to VBAT. The package supports RoHS-compliant lead-free assembly (peak reflow ≤245°C) and requires thermal contact between the exposed pad and a VBAT-biased copper plane for reliable power dissipation management.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LE57D111DJC, LE57D111BTCT delivers superior thermal performance via its eTQFP package and exposed VBAT pad, while ZL5711BCT offers identical functionality with improved reliability margins - making LE57D111BTCT optimal for cost-sensitive, high-density linecards and ZL5711BCT preferred for mission-critical industrial deployments.

Availability

LE57D111BTCT is available at Aetrix Electronics and suitable for Central Office linecards, Digital Loop Carrier systems, payphone terminal interfaces, and multi-country VoIP gateways requiring stable component supply, long-lifecycle support, and regulatory-compliant telephony performance.

Supply support for LE57D111BTCT 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 communications ICs, acquired by Microsemi in 2011. Its products targeted carrier-grade telephony, timing, and RF infrastructure.

The LE57D111BTCT belongs to the VE580 Series dual SLIC family, engineered specifically for high-density, low-power POTS linecards meeting stringent international telephony standards including China's GF002-9002.1.

FAQ

What is the maximum allowable VBAT voltage for LE57D111BTCT?

The absolute maximum VBAT rating for LE57D111BTCT is –61 V with respect to AGND. However, the guaranteed operating range is –39 V to –58 V. Operation beyond –58 V may cause overvoltage stress on internal protection circuits and is not characterized for reliability or performance. Always refer to the LE57D111BTCT datasheet Section 5.1 Absolute Maximum Ratings for safe design margins.

How does the IREF resistor set both loop current and off-hook detection threshold in LE57D111BTCT?

In LE57D111BTCT, the IREF resistor directly programs the constant-current feed level; the off-hook detection threshold is internally derived as approximately 1/3 of that programmed loop current. For example, a 15 kΩ IREF yields ~10 mA loop current and ~3.3 mA off-hook threshold in Active state. This coupling simplifies BOM and ensures consistent supervision behavior across both channels of the LE57D111BTCT.

Can LE57D111BTCT operate in industrial temperature range (–40°C to +85°C)?

Yes, LE57D111BTCT is specified and production-tested for operation across –40°C to +85°C ambient temperature, complying with Bellcore GR-357-CORE Component Reliability Assurance Requirements. Electrical characterization and screening are performed across this full industrial range, ensuring stable loop feed, accurate off-hook detection, and thermal shutdown functionality under extreme environmental conditions.

What is the purpose of the TMG1 and TMG2 pins on LE57D111BTCT?

The TMG1 and TMG2 pins on LE57D111BTCT provide dedicated thermal management outputs for each channel. Connecting an external resistor (RTMG) from TMGx to VBAT diverts power away from the silicon die, reducing junction temperature rise during high-load conditions like long-loop active operation. This feature is essential for maintaining reliability and avoiding thermal shutdown in densely packed linecards using LE57D111BTCT.

Is LE57D111BTCT pin-compatible with ZL5711BCT?

Yes, LE57D111BTCT is pin-compatible with ZL5711BCT - both use the same 44-pin eTQFP package, identical pinout, and share functional equivalence across all I/O, power, and control signals. ZL5711BCT is a direct revision offering enhanced ESD immunity (JESD22 Class 1C) and extended qualification, making it a drop-in replacement for LE57D111BTCT in new and existing designs.