STMicroelectronics M74HC138RM13TR

Overview

M74HC138RM13TR from STMicroelectronics is a high-speed CMOS 3-to-8 line decoder with inverting outputs, designed for address decoding and data routing in memory systems and digital logic control. It operates from 2V to 6V, delivers typical propagation delay of 13ns at 6V, supports ±4mA output drive, and features three enable inputs (G1, G2A, G2B) for cascading. Used in microcontroller peripheral selection and FPGA I/O expansion.

For engineers reviewing the M74HC138RM13TR datasheet, M74HC138RM13TR pinout, M74HC138RM13TR application, or M74HC138RM13TR equivalent, key selection criteria include supply voltage range (2–6V), inverting 3-to-8 decode function, TSSOP-16 package compatibility, and guaranteed 4mA output sink/source capability across industrial temperature range (−55°C to +125°C).

Technical Context

The M74HC138RM13TR implements a fully decoded 3-bit binary input (A, B, C) to eight active-low outputs (Y0–Y7), with three independent enable controls enabling hierarchical addressing. Its silicon gate C2MOS process ensures low static current (≤4µA at 25°C) and high noise immunity (≥28% VCC).

Propagation delays are balanced (tPLH ≅ tPHL), and output transition times remain consistent across VCC (7–30ns typ. at 4.5–6V). All inputs include ESD protection diodes, and outputs meet symmetrical |IOH| = |IOL| ≥ 4mA (min) under defined load conditions.

Key Specifications

Pinout & Package

TSSOP-16 package: 4.9 × 6.4 mm body, 0.65 mm pitch, exposed pad not present, JEDEC MO-153 compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 decoder applications.

Compared with SN74HC138PWR and 74AHC138T, the M74HC138RM13TR uniquely balances extended temperature operation (−55°C to +125°C), robust 28% VCC noise immunity, and proven reliability in safety-critical automotive and industrial control systems - making it the preferred choice where environmental ruggedness and long-term stability are non-negotiable.

Availability

M74HC138RM13TR is available at Aetrix Electronics and suitable for memory address decoding, peripheral selection logic, FPGA I/O expansion, and automotive body control modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for M74HC138RM13TR 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, designing and manufacturing analog, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The M74HC138 belongs to ST's high-speed CMOS logic family, engineered specifically for low-power, high-noise-immunity digital interfacing in harsh environments - including engine control units, programmable logic controllers, and medical diagnostic equipment.

FAQ

What is the maximum operating frequency supported by M74HC138RM13TR?

The M74HC138RM13TR does not specify a maximum clock frequency, as it is a combinational logic device. Its usable switching rate is determined by propagation delay (13ns typ. at 6V) and system-level timing margins. In practice, it reliably supports address decode operations up to 33 MHz bus cycles when paired with compatible drivers and loads, assuming CL ≤ 50 pF and proper PCB layout.

Can M74HC138RM13TR drive LEDs directly?

No - M74HC138RM13TR outputs are rated for ±4mA (min) at VCC = 4.5V, insufficient for most indicator LEDs requiring 5–20mA. It can drive LED cathodes only with external current-limiting resistors and series transistors or MOSFETs. Direct LED connection risks violating VOL/VOL specs and degrading output rise/fall times due to excessive capacitive and resistive loading.

Is M74HC138RM13TR pin-compatible with 74LS138 in TSSOP-16?

Yes - M74HC138RM13TR uses identical TSSOP-16 pinout and logic function as 74LS138, but operates at higher voltage (2–6V vs. 4.75–5.25V) and delivers CMOS-level noise immunity and fanout. No level-shifting is required, though timing behavior differs due to lower propagation delay and absence of TTL input thresholds.

Does M74HC138RM13TR require external pull-up resistors on outputs?

No - outputs are actively driven high or low; pull-ups are unnecessary and would conflict with the inverting logic function. Each Yx output sources current when inactive (high) and sinks current when active (low). Adding pull-ups increases power dissipation, slows rise time, and may violate VOH/VOL specifications under load.