Texas Instruments SN65ELT21DGK

Overview

SN65ELT21DGK from Texas Instruments is a 5-V PECL-to-TTL level translator in VSSOP-8 package, delivering 3 ns typical propagation delay, 24-mA TTL output drive, deterministic low-level output under open or sub-1.3-V inputs, and built-in temperature compensation. It enables reliable clock/data transmission over backplanes in telecom and industrial timing systems.

For engineers reviewing the SN65ELT21DGK datasheet, SN65ELT21DGK pinout, SN65ELT21DGK application, or SN65ELT21DGK equivalent, this page provides verified functional identity, validated SOIC/VSSOP package mapping, confirmed PECL input swing (200–1000 mV), TTL output voltage specs (VOH ≥2.4 V at –3 mA, VOL ≤0.5 V at 24 mA), and drop-in compatibility context with MC10ELT21/MC100ELT21.

Technical Context

The SN65ELT21DGK implements differential PECL-to-single-ended TTL translation using internal pull-down resistors (50 kΩ) and a dedicated VBB reference output (3.62–3.74 V) for single-ended biasing or AC-coupled input termination. Its architecture ensures deterministic Q output behavior during open or undriven conditions.

It operates across VCC = 4.2 V to 5.7 V with guaranteed performance up to 200 MHz switching frequency and 5–20 ps RMS random jitter. Input common-mode range spans 2.2 V to 5.0 V in differential mode, while TTL output meets standard logic thresholds under full temperature range (–40°C to 85°C).

Key Specifications

Pinout & Package

VSSOP-8 package (DGK), 1.1 mm max height, 3.0 mm × 3.0 mm body, 0.65 mm lead pitch, RoHS-compliant NiPdAu lead finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PECL-to-TTL translation applications.

Compared with MC10ELT21, SN65ELT21DGK reduces system-level component count via integrated VBB and temperature compensation; compared with SN65ELT22DGK, it offers lower power and simpler layout for single-channel use cases where channel density is not constrained.

Availability

SN65ELT21DGK is available at Aetrix Electronics and suitable for backplane interconnects, clock distribution networks, and industrial PLC I/O requiring stable component supply, consistent parametric performance, and long-term lifecycle support.

Supply support for SN65ELT21DGK 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies, with over 90 years of innovation in precision analog and high-speed interface solutions.

The SN65ELT21DGK belongs to TI's high-speed interface translator product line, designed specifically for robust PECL-to-TTL signal conversion in telecom infrastructure, industrial automation, and test instrumentation where deterministic timing and noise immunity are critical.

FAQ

What is the primary function of the SN65ELT21DGK?

The SN65ELT21DGK is a single-channel 5-V PECL-to-TTL translator that converts differential PECL input signals into TTL-compatible output levels. It features deterministic output behavior under open or undriven inputs, built-in VBB reference generation, and operates across –40°C to +85°C. The SN65ELT21DGK supports high-speed data and clock transmission with 3 ns typical propagation delay and 200 MHz maximum switching frequency.

Does the SN65ELT21DGK require external biasing components?

No - the SN65ELT21DGK integrates a VBB reference output (3.62–3.74 V) that eliminates the need for external bias resistors when interfacing single-ended PECL sources. When used, VBB must be decoupled with a 0.01 µF capacitor to VCC and loaded with less than ±0.5 mA. For differential operation, no external biasing is required. The SN65ELT21DGK also includes internal 50 kΩ pull-down resistors to ensure deterministic low-level output under open-input conditions.

Is the SN65ELT21DGK pin-compatible with older industry-standard translators?

Yes - the SN65ELT21DGK is explicitly documented by Texas Instruments as drop-in compatible with MC10ELT21 and MC100ELT21 in the same SOIC-8 or VSSOP-8 footprint. Pin assignments, electrical interface, and functional behavior match these legacy devices, enabling direct replacement without PCB modification. However, the SN65ELT21DGK adds integrated VBB and temperature compensation not present in the MC10x series.

What are the key thermal characteristics of the SN65ELT21DGK?

The SN65ELT21DGK in VSSOP-8 (DGK) package has a junction-to-board thermal resistance (θJB) of 120°C/W and junction-to-case (θJC) of 74°C/W. At TA = 85°C, its power rating is 188 mW (Low-K board) or 211 mW (High-K board), with derating starting above 25°C at 5 mW/°C. These values are validated per JEDEC standards and assume proper PCB copper pour and airflow >500 lfpm, as specified in the SN65ELT21DGK datasheet.

Can the SN65ELT21DGK operate outside the standard 5-V supply range?

Yes - the SN65ELT21DGK is rated for VCC = 4.2 V to 5.7 V, supporting operation across ±0.8 V tolerance relative to nominal 5 V. All DC and AC specifications - including VOH (≥2.4 V at –3 mA), VOL (≤0.5 V at 24 mA), and propagation delay (2–4.5 ns) - are guaranteed across this full range and the entire –40°C to +85°C temperature span. The SN65ELT21DGK does not support operation below 4.2 V or above 5.7 V, as absolute maximum ratings cap VCC at 6 V.