onsemi MM74HC594M

Overview

MM74HC594M from Fairchild Semiconductor is an 8-bit serial-in, parallel-out shift register with separate output storage registers, featuring dual positive-edge-triggered clocks (SCK for shift register, RCK for storage register), direct asynchronous clears (SCLR and RCLR), and cascading capability via Q'H serial output. It operates from 2V to 6V, supports up to 30 MHz shift frequency at 4.5V, and drives 15 LS-TTL loads - used in LED matrix drivers, display controllers, and I/O expansion circuits.

For engineers reviewing the MM74HC594M datasheet, pinout, applications, or equivalent options, key selection considerations include its dual-clock architecture, independent clear functions, guaranteed AC timing across voltage range, cascading support, and SOIC-16 packaging for space-constrained PCB layouts.

Technical Context

The MM74HC594M integrates two synchronized but independently controlled register stages: a serial-input shift register feeding an 8-bit D-type output latch. Its SCK and RCK inputs accept positive-edge-triggered clocks, enabling precise separation of data shifting and output latching - critical for glitch-free display updates. The SCLR and RCLR pins provide asynchronous reset for each stage, allowing independent initialization without affecting the other.

Designed for compatibility with the 74LS family, the MM74HC594M uses silicon-gate CMOS technology to deliver LS-TTL drive strength (±35 mA per output) with HC-level quiescent current (≤80 µA). Input clamping diodes protect against ESD, and operation is specified from −40°C to +85°C with VCC = 2V–6V.

Key Specifications

Pinout & Package

MM74HC594M is housed in a 16-lead SOIC package (JEDEC MS-012, 0.150" narrow body), with standard 1.27 mm pitch and gull-wing leads compatible with reflow soldering.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit shift-and-latch register applications.

Compared with SN74HC595N and 74AHC594PW, the MM74HC594M uniquely balances strong output drive, independent clear control, and wide-voltage operation - making it optimal for industrial displays and I/O expanders requiring reliability over raw speed or minimal drive.

Availability

MM74HC594M is available at Aetrix Electronics and suitable for LED matrix display drivers, microcontroller I/O expansion, and industrial control panels requiring stable component supply and long-term manufacturability.

Supply support for MM74HC594M 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 and supported.

The MM74HC594M belongs to Fairchild's 74HC high-speed CMOS logic family, designed specifically for drop-in replacement of 74LS devices while delivering lower power, higher noise immunity, and broader supply voltage tolerance.

FAQ

What is the function of the Q'H pin on the MM74HC594M?

The Q'H pin on the MM74HC594M is the inverted serial output of the shift register, providing the complement of the most-recently-shifted bit. It enables cascading by connecting to the SER input of a downstream MM74HC594M device. This allows multiple MM74HC594M units to be linked for extended parallel output widths without additional MCU GPIOs or timing complexity.

Can the MM74HC594M operate reliably at 3.3V?

Yes, the MM74HC594M is fully specified for operation from 2V to 6V, including 3.3V nominal supply. At VCC = 3.3V, it maintains guaranteed logic thresholds (VIH ≥ 2.1V, VIL ≤ 1.2V), supports >15 MHz shift frequency, and delivers ≥24 mA output drive - making it interoperable with modern 3.3V microcontrollers and FPGA I/O banks without level-shifting circuitry.

How does the MM74HC594M differ from the SN74HC595 in terms of control logic?

The MM74HC594M features separate SCLR (shift register clear) and RCLR (storage register clear) inputs, enabling independent reset of each register stage. In contrast, the SN74HC595 uses a single SRCLR that clears both shift and storage registers simultaneously. This distinction makes the MM74HC594M preferable in applications requiring output latches to retain state while reloading the shift register - such as flicker-free display updates.

What is the maximum capacitive load the MM74HC594M can drive on its QA–QH outputs?

The MM74HC594M is characterized for CL = 50 pF and CL = 150 pF in its AC Electrical Characteristics table. Propagation delays remain within specification up to 150 pF per output. For reliable signal integrity beyond this, external series termination or buffer isolation is recommended - especially in high-speed or noise-sensitive environments where the MM74HC594M drives long traces or multiple gate inputs.

Is the MM74HC594M RoHS compliant and lead-free?

Yes, the MM74HC594M manufactured under Fairchild's post-2006 production lines meets RoHS Directive 2011/65/EU requirements and is lead-free. The SOIC package (M16A) uses matte tin lead finish, and the device carries appropriate marking (e.g., "Pb-Free" or "RoHS Compliant") on reel labels and datasheet revision pages - consistent with ON Semiconductor's continued support of the legacy Fairchild logic portfolio.