onsemi 74LVTH244SJX

Overview

74LVTH244SJX from Fairchild Semiconductor is a low-voltage octal buffer/line driver with 3-STATE outputs, designed for memory address and clock driving in 3.3V systems interfacing to 5V TTL buses. It features bushold inputs (eliminating external pull-ups), ±32mA/64mA drive capability, and operates from 2.7V to 3.6V across –40°C to +85°C.

For engineers reviewing the 74LVTH244SJX datasheet, pinout, applications, or equivalent options, key selection criteria include bushold input support, 3-STATE bus isolation timing (tPZH ≤ 5.3ns), high-current drive (IOL = 64mA), and SOIC-20 (M20D) package compatibility with EIAJ TYPE II footprint.

Technical Context

The 74LVTH244SJX implements dual 4-bit non-inverting buffers with independent 3-STATE control (OE1/OE2), enabling selective bus segment isolation. Its bushold circuitry actively maintains input logic state without external biasing - confirmed for all eight data inputs (I0–I7) per datasheet Section 4.

It uses advanced BiCMOS technology to achieve ABT-class speed (tPLH/tPHL ≤ 4.2ns at VCC = 2.7V) while maintaining low static current (ICCZ = 0.19mA). The device supports live insertion/extraction and power-up/down high-impedance behavior to prevent bus glitches during hot-swap events.

Key Specifications

Pinout & Package

74LVTH244SJX is packaged in a 20-lead Small Outline Package (SOP), EIAJ TYPE II, 5.3mm wide (package code M20D), with standard SOIC pin spacing (1.27mm pitch) and gull-wing leads.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal buffer applications.

Compared with SN74LVC244APWR and 74ALVC244MTCX, the 74LVTH244SJX uniquely delivers bushold-enabled 5V-tolerant inputs and 64mA sink capability in a single 20-pin SOP package - critical for industrial backplane and memory subsystem designs requiring zero-input-bias robustness.

Availability

74LVTH244SJX is available at Aetrix Electronics and suitable for memory subsystem design, industrial bus interface, and clock distribution applications requiring stable component supply, long-term lifecycle support, and JEDEC-compliant lead-free packaging.

Supply support for 74LVTH244SJX 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in analog and mixed-signal ICs, acquired by ON Semiconductor in 2016; its legacy logic portfolio remains widely deployed in industrial and computing infrastructure.

The 74LVTH244SJX belongs to Fairchild's LVT/H family of low-voltage TTL-compatible buffers, engineered specifically for 3.3V systems interfacing with 5V buses in memory, clock, and peripheral expansion applications.

FAQ

What is the bushold feature of the 74LVTH244SJX and how does it affect PCB design?

The bushold feature in the 74LVTH244SJX actively retains the last valid logic state on each data input (I0–I7) without external pull-up or pull-down resistors. This eliminates the need for 10kΩ biasing networks on unused inputs, reducing component count, board area, and potential noise coupling. For the 74LVTH244SJX, bushold current is specified at ±75µA (VI = 0.8V/2.0V, VCC = 3.0V), ensuring reliable state retention even under marginal noise conditions.

Can the 74LVTH244SJX safely interface between a 3.3V microcontroller and a 5V EEPROM?

Yes - the 74LVTH244SJX supports 5V-tolerant inputs (VI up to 5.5V) while operating from a 3.3V supply, making it suitable for driving 5V EEPROM address/data/control lines. Its outputs swing rail-to-rail (VOL ≤ 0.55V at IOL = 64mA, VOH ≥ VCC–0.2V), meeting 5V TTL input thresholds. However, verify EEPROM input capacitance against the 74LVTH244SJX's 6pF COUT and 4.2ns max tPHL to ensure timing compliance.

What is the maximum clock frequency supported by the 74LVTH244SJX in a bus-driving role?

The 74LVTH244SJX does not specify a maximum clock frequency directly, but its AC performance supports reliable operation up to 100MHz in typical bus applications. With tPLH/tPHL ≤ 4.2ns (VCC = 2.7V) and output skew ≤ 1.0ns, it maintains signal integrity for data rates where period > 10ns - validated in SOIC packages per datasheet Section 5. For 33MHz PCI clock distribution, the 74LVTH244SJX meets setup/hold margin requirements with margin.

Does the 74LVTH244SJX require decoupling capacitors, and if so, what value and placement is recommended?

Yes - Fairchild recommends minimum 0.1µF ceramic decoupling capacitors placed within 5mm of the 74LVTH244SJX VCC (pin 20) and GND (pin 10) pads. For systems with high di/dt switching (e.g., all eight outputs toggling simultaneously), add a bulk 4.7µF tantalum capacitor near the power entry point. This mitigates supply bounce caused by the 64mA transient sink current and ensures stable 3.3V regulation during output transitions.

How does the 74LVTH244SJX handle power-up sequencing when VCC ramps slowly?

The 74LVTH244SJX incorporates power-up high-impedance circuitry that forces all outputs (O0–O7) into 3-STATE before VCC reaches 2.0V, preventing bus contention during brown-out or soft-start conditions. Per datasheet Section 3, this behavior is guaranteed across –40°C to +85°C and eliminates need for external reset-controlled OE gating. The 74LVTH244SJX also exhibits power-down high-Z, maintaining isolation until VCC drops below 0.5V.