Texas Instruments SN65ELT20D

Overview

SN65ELT20D from Texas Instruments is a 5-V TTL-to-differential PECL translator in SOIC-8 package, delivering 1.25-ns max propagation delay, 400-MHz max switching frequency, and ±0.5-ps RMS random jitter. It operates across –40°C to 85°C with VCC = 4.2 V to 5.7 V and serves as a low-skew clock/data level shifter for backplane signaling.

For engineers reviewing the SN65ELT20D datasheet, SN65ELT20D pinout, SN65ELT20D application, or SN65ELT20D equivalent, this device supports high-speed interface bridging between TTL logic domains and PECL differential buses in telecom timing, FPGA clock distribution, and industrial control systems.

Technical Context

The SN65ELT20D implements a single-channel unidirectional translation path: TTL input (D) drives complementary PECL outputs (Q, Q̅), with no internal termination-external 50-Ω pull-up to VCC – 2 V required per output. Its flow-through pinout minimizes PCB trace skew and eliminates layer stacking complexity.

It features built-in temperature compensation to stabilize output voltage levels across –40°C to 85°C, and its PECL DC output swing (VOH/VOL = 3915–4120 mV / 3170–3380 mV at VCC = 5 V) ensures robust noise margin against EMI in dense routing environments.

Key Specifications

Pinout & Package

SN65ELT20D is housed in an industry-standard SOIC-8 (D) package, 3.9 mm × 4.9 mm body, 1.75 mm max height, with NiPdAu lead finish and moisture sensitivity level (MSL) 1 (260°C peak reflow).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC100ELT20DG and SN65LVDS100DR, the SN65ELT20D uniquely delivers PECL-level outputs from a single positive 5-V supply while maintaining sub-ns delay and ultra-low jitter-making it the optimal choice for upgrading legacy TTL clock trees to differential signaling without redesigning power architecture.

Availability

SN65ELT20D is available at Aetrix Electronics and suitable for backplane clock distribution, FPGA I/O interfacing, and industrial PLC timing modules requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for SN65ELT20D 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 decades of expertise in high-speed interface solutions.

The SN65ELT20D belongs to TI's high-speed logic translator product line, engineered specifically for reliable TTL-to-PECL level conversion in telecom infrastructure, industrial automation, and test equipment where timing precision and noise immunity are critical.

FAQ

What is the recommended termination for SN65ELT20D outputs?

The SN65ELT20D outputs require 50-Ω resistive termination to VCC – 2 V (not to GND or VCC). This matches standard PECL bus impedance and establishes correct common-mode voltage. Incorrect termination-such as AC-coupling without proper DC bias or using 50-Ω to GND-causes output distortion, increased jitter, and failure to meet VOH/VOL specifications. The SN65ELT20D datasheet Figure 1 shows the exact configuration.

Does SN65ELT20D support operation at 3.3 V?

No, SN65ELT20D is specified only for VCC = 4.2 V to 5.7 V. It lacks internal regulation or level-shifting circuitry for 3.3-V operation. Attempting to power SN65ELT20D at 3.3 V results in undefined output states, excessive ICC variation, and failure to meet AC timing specs-including propagation delay and jitter. For 3.3-V systems, consider TI's SN65LVDS100 or SN65LVDS20 instead.

Can SN65ELT20D drive multiple PECL loads simultaneously?

SN65ELT20D is rated for one standard PECL load per output (50-Ω to VCC – 2 V). Driving multiple parallel loads increases capacitive loading, degrading rise/fall times, increasing jitter, and potentially violating VOH/VOL limits. For fanout >1, TI recommends using a dedicated PECL fanout buffer (e.g., SN65EL10) downstream of SN65ELT20D-not connecting multiple loads directly to its Q/Q̅ pins.

Is SN65ELT20D pin-compatible with SN65ELT20DR?

Yes, SN65ELT20D and SN65ELT20DR share identical SOIC-8 (D) package, pinout, electrical characteristics, and thermal profile-the only difference is packaging format (tube vs. tape-and-reel). Both use the same die, marking "ELT20", and MSL Level-1 rating. SN65ELT20DR.B is the tape-and-reel variant with same part marking and performance as SN65ELT20D.

What happens if the D input is left floating on SN65ELT20D?

If the D input is left floating, the SN65ELT20D output state becomes indeterminate-Q and Q̅ may oscillate, settle unpredictably, or enter high-impedance-like behavior due to internal TTL input stage ambiguity. TI explicitly warns against floating inputs in the SN65ELT20D datasheet Section 6.1. Always tie unused D inputs to GND (for LOW) or VCC (for HIGH) via ≤1-kΩ resistor to ensure deterministic operation.