Texas Instruments SN74HCS574RKSR

Overview

SN74HCS574 from Texas Instruments is an octal D-type flip-flop IC with Schmitt-trigger inputs, 3-state outputs, and flow-through pinout. It operates across 2 V to 6 V, delivers ±7.8-mA drive at 6 V, supports –40°C to +125°C ambient, and synchronizes parallel data on rising clock edges in bus-hold or noise-prone digital systems.

For engineers reviewing the SN74HCS574 datasheet, SN74HCS574 pinout, SN74HCS574 application, or SN74HCS574 equivalent, key selection criteria include its Schmitt-trigger noise immunity, 3-state bus interface capability, flow-through routing advantage, low ICC (100 nA typical), and dual-package availability (RKS VQFN and DGS VSSOP).

Technical Context

This device integrates eight independent D-type latches sharing a single rising-edge-triggered CLK and active-low OE control. All inputs feature Schmitt-trigger hysteresis (ΔVT = 0.6 V min at 6 V), enabling robust operation with slow or noisy signals without external conditioning.

Outputs are balanced CMOS 3-state drivers capable of sourcing/sinking ±7.8 mA at 6 V while maintaining VOH ≥ 5.4 V and VOL ≤ 0.33 V under load. The flow-through pinout (D1–D8 on left, Q1–Q8 on right, CLK/OE centered) minimizes trace crossovers in dense PCB layouts.

Key Specifications

Pinout & Package

The SN74HCS574 is packaged in a 20-pin RKS (VQFN) with 4.50 mm × 2.50 mm body size and wettable flank terminations for automated optical inspection. Thermal pad is optional (GND or floating).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal D-type flip-flop applications.

Compared with SN74HCS374PWR and 74LVC574APWJ, the SN74HCS574 uniquely combines wide-voltage operation, integrated noise immunity, and optimized pinout - making it the only choice for robust, layout-efficient 8-bit data capture in harsh or mixed-supply environments.

Availability

SN74HCS574 is available at Aetrix Electronics and suitable for industrial automation, automotive body control modules, and IoT edge sensor hubs requiring stable component supply across extended temperature and voltage ranges.

Supply support for SN74HCS574 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 logic solutions for industrial, automotive, and communications markets.

The SN74HCS574 belongs to TI's HCS logic family, designed specifically for low-power, noise-tolerant digital interfacing in demanding real-world environments where signal integrity and supply flexibility are critical.

FAQ

What is the maximum clock frequency supported by the SN74HCS574?

The SN74HCS574 supports a maximum clock frequency of 135 MHz at 6 V supply, 120 MHz at 4.5 V, and 49 MHz at 2 V. These values are measured with CL = 50 pF and reflect guaranteed timing performance across the full operating temperature range. The SN74HCS574 achieves this speed while maintaining low power consumption and noise immunity - a balance not found in standard HCMOS or LVC variants.

Does the SN74HCS574 require external pull-up or pull-down resistors on unused inputs?

No, unused inputs on the SN74HCS574 do not require external pull-up or pull-down resistors due to its Schmitt-trigger architecture, which prevents floating-input oscillation and excessive current draw. However, TI recommends tying unused inputs to VCC or GND for predictable startup behavior and ESD robustness. The SN74HCS574's input leakage remains within ±1000 nA even when held at intermediate voltages, but fixed termination ensures deterministic logic states.

Can the SN74HCS574 drive a 100-pF load reliably?

The SN74HCS574 is characterized and specified for loads ≤50 pF; driving 100-pF loads exceeds the recommended condition and degrades timing (increased tpd, reduced fmax) and output voltage margins (VOH/VOL). While functional operation may occur, SN74HCS574 timing parameters like 10.3 ns propagation delay and 135 MHz max frequency are not guaranteed beyond 50 pF. For heavier loads, add a buffer stage or select a higher-drive logic family.

Is the thermal pad on the RKS package of the SN74HCS574 required to be connected?

The thermal pad on the SN74HCS574 RKS (VQFN) package is optional: it may be connected to GND for improved thermal dissipation and ESD performance, or left floating with no electrical impact. TI's datasheet explicitly states "Do not connect to any other signal or supply." No thermal derating is required for standard operation, but grounding the pad lowers θJA from 83.2°C/W to ~65°C/W in typical PCB layouts - beneficial for sustained high-frequency operation in compact enclosures.

How does the SN74HCS574 handle power-up initialization?

At power-up, the stored state of all eight flip-flops in the SN74HCS574 is unknown (Q0 undefined), and outputs remain in high-impedance until OE is asserted low. The SN74HCS574 does not include power-on reset circuitry; therefore, the first valid clock edge after OE activation determines initial output states. To ensure deterministic behavior, systems must provide a known data pattern and synchronized CLK/OE sequence during startup - a requirement explicitly documented in the SN74HCS574 functional description.