STMicroelectronics M74HC161TTR

Overview

M74HC161TTR from STMicroelectronics is a high-speed CMOS synchronous 4-bit binary presettable counter with asynchronous clear, synchronous parallel load, and cascading enable logic (TE/PE) for N-bit counter expansion. It operates from 2V to 6V, delivers 62 MHz max clock frequency at 6V, features symmetrical 4 mA output drive, and is pin- and function-compatible with standard 74-series 161 counters. It is used in digital timing control, address sequencing, and event counting circuits in industrial PLC modules and instrumentation.

For engineers reviewing the M74HC161TTR datasheet, M74HC161TTR pinout, M74HC161TTR application, or M74HC161TTR equivalent, key selection criteria include its synchronous preset capability, asynchronous clear behavior, carry-out propagation delay (≤38 ns at 4.5V), and TSSOP-16 package compatibility with space-constrained PCB layouts.

Technical Context

The M74HC161TTR implements a 4-bit synchronous binary counter using silicon gate C2MOS technology. Its rising-edge-triggered clock input controls all state transitions, while asynchronous CLEAR (active-low) forces QA–QD to 0 regardless of clock phase. Preset data A–D loads synchronously on the next rising clock edge when LOAD is low.

Cascading is enabled via TE (count-enable carry input) and PE (count-enable parallel input), with CARRY output asserted only when TE = HIGH and QA–QD = 1111. All inputs include ESD protection diodes, and propagation delays are balanced (tPLH ≈ tPHL) across voltage ranges.

Key Specifications

Pinout & Package

TSSOP-16 package: 4.9 × 6.4 mm body, 0.65 mm pitch, 1.2 mm max height, lead-free and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous 4-bit counter applications.

Compared with SN74HC161PWR and 74HC161D,653, the M74HC161TTR offers identical counter functionality and timing performance but differs in package mechanicals (TSSOP-16) and manufacturer-specific reliability testing - making it optimal for space-constrained, high-density industrial PCBs requiring STMicroelectronics' automotive-grade process traceability.

Availability

M74HC161TTR is available at Aetrix Electronics and suitable for industrial timer modules, PLC I/O sequencing, and digital panel meter address generation requiring stable component supply and long-term lifecycle support.

Supply support for M74HC161TTR 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 industrial, automotive, and consumer applications.

The M74HC161TTR belongs to ST's high-speed HC logic product line, engineered for robust operation across extended temperature ranges (−55°C to +125°C) in harsh industrial control environments.

FAQ

Is M74HC161TTR pin-compatible with older 74LS161 devices?

No - while functionally equivalent, M74HC161TTR uses CMOS input thresholds (VIH ≥ 3.15 V at 4.5 V VCC) versus TTL thresholds in 74LS161. Direct replacement requires verifying input drive strength and voltage levels; level-shifting may be needed in mixed-logic systems.

What is the minimum pulse width required for the CLEAR input?

The minimum CLEAR pulse width is 13 ns (max.) at VCC = 6 V and TA = −55°C to +125°C. At 4.5 V, it is 22 ns. This ensures reliable asynchronous reset even under worst-case voltage and temperature conditions.

Can M74HC161TTR operate reliably at 2.0 V supply?

Yes - it is fully specified down to 2.0 V, with fMAX = 6.2 MHz (min.), VIH = 1.5 V (min.), and VOL ≤ 0.1 V at 20 µA load. However, propagation delays increase significantly (e.g., tPLH up to 190 ns), so timing-critical paths must be re-verified.

Does the CARRY output drive standard TTL loads?

No - CARRY is a CMOS output with VOH ≥ 4.4 V and VOL ≤ 0.26 V at 4 mA load (VCC = 4.5 V), meeting HC logic levels but not TTL's 2.4 V VIH requirement. Interfacing to TTL inputs requires a pull-up resistor or buffer stage.