Texas Instruments SN74HCS244RKSR

Overview

SN74HCS244 from Texas Instruments is an octal non-inverting buffer/line driver with Schmitt-trigger inputs and 3-state outputs, configured as two independent 4-channel banks (1A1–1A4 / 2A1–2A4) each controlled by dedicated active-low output enable pins (1OE, 2OE). It operates from 2 V to 6 V, delivers ±7.8 mA output drive at 6 V, features 100 nA typical supply current, and supports –40°C to +125°C ambient operation - used for noise-immune signal buffering in industrial I/O expansion and microcontroller bus isolation.

For engineers reviewing the SN74HCS244 datasheet, SN74HCS244 pinout, SN74HCS244 application, or SN74HCS244 equivalent, key selection criteria include Schmitt-trigger hysteresis (min 0.2 V at 2 V), propagation delay (6 ns typ at 6 V), 3-state disable timing (8 ns typ), input leakage (±100 nA max), and VQFN-20 (RKS) package compatibility with automated optical inspection via wettable flanks.

Technical Context

The SN74HCS244 implements dual-bank CMOS logic with independent active-low 3-state control: 1OE enables Bank 1 outputs (1Y1–1Y4), 2OE enables Bank 2 outputs (2Y1–2Y4). Each input incorporates Schmitt-trigger architecture providing hysteresis (ΔVT = 0.6 V min at 6 V), enabling reliable operation with slow-rising or noisy signals without oscillation.

Its balanced push-pull outputs support bidirectional current sourcing/sinking up to ±7.8 mA at 6 V while maintaining rail-to-rail VOH/VOL (e.g., VOL = 0.22 V max at 6 V, 7.8 mA sink). The device uses standard CMOS process with ESD protection (±4 kV HBM), operates across full industrial temperature range, and requires no external pull-ups on OE pins when tied to VCC for power-up high-impedance safety.

Key Specifications

Pinout & Package

RKS package is a 20-pin VQFN (4.50 mm × 2.50 mm) with exposed thermal pad; compatible with reflow soldering and AOI inspection due to wettable flanks.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal buffer with Schmitt-trigger and 3-state applications.

Compared with SN74LVCH244A and 74LVC244APW, the SN74HCS244 uniquely combines wide 2–6 V operation, true Schmitt-trigger noise rejection, and automotive-grade temperature range in a manufacturable VQFN package - making it the only choice for mixed-voltage industrial sensing and legacy 5-V bus extension.

Availability

SN74HCS244 is available at Aetrix Electronics and suitable for industrial I/O expansion, microcontroller bus isolation, switch debounce interface, and automotive body control module applications requiring stable component supply across extended temperature and voltage ranges.

Supply support for SN74HCS244 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 delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The SN74HCS244 belongs to TI's HCS logic family - designed specifically for low-power, noise-immune digital interfacing in harsh environments where signal integrity and supply flexibility are critical.

FAQ

What is the maximum recommended capacitive load for SN74HCS244?

The SN74HCS244 is characterized and specified for loads ≤50 pF. Driving larger capacitances increases propagation delay and transition time, potentially violating setup/hold timing in synchronous systems. While operation beyond 50 pF is possible, signal integrity must be verified per application - especially with long traces or unterminated stubs. The SN74HCS244 datasheet specifies all timing parameters at CL = 50 pF.

Does SN74HCS244 require external pull-up resistors on its OE pins?

No - SN74HCS244 does not require external pull-ups on 1OE or 2OE for functional operation, but tying them to VCC via a resistor (e.g., 10 kΩ) ensures outputs remain in high-impedance state during power-up/power-down sequences. This prevents bus contention or unintended signal assertion before MCU firmware initializes the enable controls. The SN74HCS244 itself has no internal pull-ups on OE pins.

Can SN74HCS244 operate reliably with 1.8-V input signals?

Yes - SN74HCS244 supports 2-V minimum supply, and its Schmitt-trigger inputs have VT+ thresholds as low as 0.7 V (at 2 V VCC) and VT− as low as 0.3 V. A 1.8-V logic HIGH exceeds VT+ across the full voltage range, ensuring robust recognition. However, ensure the 1.8-V source can drive the SN74HCS244's input capacitance (5 pF) and leakage (±100 nA) without excessive droop or delay.

How does the thermal pad on the RKS package affect SN74HCS244 performance?

The exposed thermal pad on the SN74HCS244 RKS (VQFN) package lowers junction-to-board thermal resistance (RθJB = 57.4°C/W), improving power dissipation capability and reducing steady-state junction temperature by up to 15°C under continuous 7.8-mA output loading. TI recommends connecting the pad to GND for both thermal and EMI benefits - though floating is electrically permissible per datasheet guidance.

Is SN74HCS244 pin-compatible with older 74HC244 variants?

No - SN74HCS244 is not pin-compatible with standard 74HC244. While both are octal 3-state buffers, SN74HCS244 adds Schmitt-trigger inputs and revised input threshold behavior. Pin assignments differ: SN74HCS244 uses dedicated 1OE/2OE pins (pins 1 and 19), whereas 74HC244 uses single OE pins (pins 1 and 19 in DIP-20, but different mapping in SOIC-20). Always verify pin functions using the SN74HCS244 datasheet Figure 5-1 before board reuse.