Texas Instruments SN74AC564NSR

Overview

SN74AC564 from Texas Instruments is an octal D-type edge-triggered flip-flop with inverting 3-state outputs, designed for bus-oriented applications requiring high-speed data latching and bidirectional bus driving. It operates from 2V to 6V V_CC, supports 5V and 3.3V logic systems, delivers ≤9ns propagation delay at 5V, and features flow-through pinout for optimized PCB layout.

For engineers reviewing the SN74AC564 datasheet, SN74AC564 pinout, SN74AC564 application, or SN74AC564 equivalent, key selection criteria include its rising-edge clock trigger, active-low 3-state output enable (OE), inverting output polarity, wide supply range compatibility, and suitability for I/O port buffering and register file implementation in industrial control and legacy computing interfaces.

Technical Context

The SN74AC564 implements eight independent D-type flip-flops sharing a common rising-edge-triggered clock (CLK) and a global active-low output enable (OE). Each Q output is the logical inverse of its corresponding D input on CLK's positive transition. OE controls all eight outputs simultaneously, placing them in high-impedance state without affecting internal latch operation.

Its AC logic family ensures TTL-compatible input thresholds and CMOS-level drive strength, with inputs tolerant up to 6V regardless of V_CC. The device supports bus-hold-free operation when unused inputs are tied to V_CC or GND, and its flow-through architecture-D inputs on one side, Q outputs on the opposite-minimizes trace crossovers in dense layouts.

Key Specifications

Pinout & Package

SN74AC564NSR uses the NS (SOIC-20) package: 12.80mm × 10.3mm body size, 20-pin narrow-body surface-mount outline with 0.635mm lead pitch. Pin 1 index is marked by a beveled corner or notch.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74ACT564DW and SN74LVC574APW, the SN74AC564 offers unique 2V–6V operation with inverting outputs and 6V-tolerant inputs - making it the only option among the three suitable for mixed-voltage 5V/3.3V bus bridging with guaranteed signal inversion and robust hot-swap capability.

Availability

SN74AC564NSR is available at Aetrix Electronics and suitable for industrial I/O expansion, legacy bus interface, memory address latching, and test equipment signal conditioning requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74AC564NSR 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 SN74AC564 belongs to TI's advanced CMOS (AC) logic family, engineered for high-speed, low-power, mixed-voltage digital interfacing in mission-critical industrial and computing infrastructure applications.

FAQ

What logic family does the SN74AC564 belong to, and how does it differ from standard TTL or CMOS?

The SN74AC564 belongs to Texas Instruments' Advanced CMOS (AC) logic family. Unlike standard TTL, it features CMOS-level power consumption (ICC < 40µA) while maintaining TTL-compatible input thresholds and 6V-tolerant inputs. Compared to standard CMOS, it delivers faster propagation delays (≤9ns at 5V) and stronger output drive (±24mA), making SN74AC564 ideal for high-speed bus interfacing where both speed and robustness are required.

Does the SN74AC564NSR support 3.3V operation, and what are the timing implications?

Yes, SN74AC564NSR fully supports 3.3V operation within its 2V–6V V_CC range. At V_CC = 3.3V ± 0.3V, it guarantees f_clock ≥ 60MHz, t_su ≤ 3ns, and t_pd ≤ 15.5ns (max). These specifications ensure reliable operation in modern 3.3V systems such as FPGA configuration interfaces or ARM-based peripheral buses, with sufficient timing margin for PCB trace delays.

What is the function of the OE pin on the SN74AC564, and how should it be handled during power-up?

The OE (Output Enable) pin on SN74AC564 is an active-low control that places all eight Q outputs in high-impedance state when asserted (OE = high). During power-up or power-down, TI recommends tying OE to V_CC via a pullup resistor (value determined by driver sink capability) to ensure outputs remain in high-Z until system initialization completes - preventing bus contention. This behavior is explicitly defined in the SN74AC564 functional description and applies to all variants including SN74AC564NSR.

Is the SN74AC564NSR pin-compatible with other members of the '564 family, such as SN74AC564DBR or SN74AC564PWR?

Yes, SN74AC564NSR is pin-compatible with all standard-package variants of the '564 family - including SN74AC564DBR (SSOP-20), SN74AC564DW (SOIC-20), and SN74AC564PWR (TSSOP-20) - because they share identical pin numbering, pin functions, and electrical behavior per TI's mechanical packaging documentation. The NSR suffix denotes the SOIC-20 package variant, and all '564 devices implement the same logic diagram, timing, and DC characteristics regardless of package type.

Can unused inputs on the SN74AC564NSR be left floating, or must they be terminated?

No, unused inputs on SN74AC564NSR must not be left floating. TI specifies in Section 4.2 that all unused inputs must be held at V_CC or GND to ensure proper device operation and prevent increased ICC or erratic behavior. Floating CMOS inputs can cause shoot-through current and oscillation; this requirement applies universally across all SN74AC564 variants, including SN74AC564NSR, and is documented in TI's application report SCBA004.