STMicroelectronics M74HC595TTR

Overview

M74HC595TTR from STMicroelectronics is an 8-bit serial-in, parallel-out shift register with output latches and 3-state outputs, designed for digital control expansion in microcontroller-based systems. It features dual independent clocks (SCK for shift register, RCK for storage register), asynchronous clear (SCLR), and cascading capability via QH' serial output. Operating from 2 V to 6 V, it delivers 59 MHz max clock frequency at 6 V and supports industrial temperature range (–55 °C to +125 °C) in TSSOP16 package.

For engineers reviewing the M74HC595TTR datasheet, M74HC595TTR pinout, M74HC595TTR application, or M74HC595TTR equivalent, key selection considerations include its 3-state output enable (G), separate shift/storage clocks enabling precise timing control, QH' cascade support, high noise immunity (28% VCC), and automotive-qualified variants for harsh environments.

Technical Context

The device implements a two-stage pipeline: an 8-bit shift register accepting serial data on SI with positive-edge-triggered SCK, followed by an 8-bit D-type storage register clocked by positive-edge RCK. Outputs QA–QH are latched and individually 3-state controlled by active-low G, while QH' provides non-inverted serial output for daisy-chaining.

All inputs include ESD protection (HBM 2 kV, MM 200 V, CDM 1 kV), and the silicon gate C2MOS process ensures low ICC (4 μA max at 25 °C) and symmetrical drive strength: |IOH| = IOL = 6 mA min for QA–QH at VCC = 4.5 V, and 4 mA min for QH'.

Key Specifications

Pinout & Package

TSSOP16 package: 4.9 mm × 6.4 mm × 1.05 mm body, 0.65 mm pitch, lead-free and RoHS-compliant per ECOPACK® specifications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74HC595DR and 74LV595PW, M74HC595TTR uniquely combines extended temperature operation (–55 °C to +125 °C), integrated QH' cascade path, and documented MM/CDM ESD ratings - making it optimal for industrial and automotive-adjacent applications demanding reliability and chainability.

Availability

M74HC595TTR is available at Aetrix Electronics and suitable for industrial control panels, automotive dashboard modules, and consumer appliance UIs requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for M74HC595TTR 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, delivering intelligent power, analog, MEMS, and microcontroller solutions for industrial, automotive, and consumer markets.

M74HC595 belongs to ST's legacy HC logic product line, engineered for robust, drop-in replacement of 74-series TTL functions with CMOS efficiency, low power, and enhanced noise immunity in harsh environments.

FAQ

What is the purpose of the separate SCK and RCK clocks?

The SCK clock controls data shifting into the 8-bit shift register, while RCK transfers the accumulated data to the output latches. This separation prevents output glitches during serial loading - data appears only after RCK asserts, enabling synchronous, deterministic updates across all QA–QH pins without disturbing ongoing system operation.

Can M74HC595TTR drive LEDs directly?

Yes - QA–QH deliver ±6 mA minimum sink/source at VCC = 4.5 V, sufficient to drive standard 2 mA LEDs with series resistors. For higher-current LEDs or multiplexed arrays, verify VOL/VOH margins at target current and ambient temperature; QH' output is limited to ±4 mA and should not be used for LED drive.

How does the SCLR pin behave during normal operation?

SCLR is an asynchronous, active-high clear that resets only the shift register (not the storage register). When asserted, it forces all internal shift stages to logic 0 regardless of SCK or SI state. It must be held low during normal serial loading; pulling high mid-sequence discards pending bits and requires reinitialization of the entire 8-bit stream.

Is M74HC595TTR pin-compatible with older 74LS595 devices?

No - while functionally equivalent and pinout-identical to 74HC595 and 74LS595, M74HC595TTR uses CMOS input thresholds (VIH ≈ 3.15 V at VCC = 4.5 V) versus TTL thresholds (VIH ≈ 2.0 V). Driving it directly from LS outputs may cause marginal high-level recognition; level-shifting or HC-family source devices are recommended for guaranteed compatibility.