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STMicroelectronics 74AC161MTR
- Part No.:
- 74AC161MTR
- Manufacturer:
- STMicroelectronics
- Category:
- Counters, Dividers
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
74AC161MTR.pdf
- Description:
- IC BINARY COUNTER 4-BIT 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,661
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Product details
Overview
74AC161MTR from STMicroelectronics is a high-speed CMOS synchronous presettable 4-bit binary counter with asynchronous clear, operating from 2V to 6V supply, featuring 125MHz max clock frequency (at 5V), 24mA output drive, and pin/function compatibility with standard 74-series 161 counters - used in digital timing control, address sequencing, and state machine logic in industrial control panels.
For engineers reviewing the 74AC161MTR datasheet, 74AC161MTR pinout, 74AC161MTR application, or 74AC161MTR equivalent, key selection criteria include synchronous preset capability, low-power quiescent current (8µA max), balanced propagation delays (tPLH ≅ tPHL), 50Ω transmission line driving, and ESD immunity (2kV).
Technical Context
The 74AC161 implements four operational modes-synchronous reset, parallel load, count-up, and hold-controlled by CLEAR, LOAD, PE (count enable), and TE (carry enable) inputs. Its master reset is asynchronous, overriding all other functions to force QA–QD low.
Counting occurs on the rising edge of CLOCK only when both PE and TE are HIGH; CARRY OUT goes HIGH at state 15 (1111) when TE is HIGH. All inputs/outputs include protection circuits for 2kV HBM ESD immunity and transient voltage tolerance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Max Clock Frequency | 125 MHz (typ.) at VCC = 5V - enables high-speed counting in real-time control loops |
| Supply Voltage Range | 2V to 6V - supports mixed-voltage system interfacing (e.g., 3.3V logic with 5V legacy buses) |
| Output Drive Strength | ±24 mA (min) - drives 50Ω transmission lines directly without external buffers |
| Quiescent Current | 8 µA (max) at TA = 25°C - suitable for battery-backed or low-power standby states |
| Propagation Delay (CLOCK→Q) | 5.0 ns (typ.) at 5V - ensures tight timing margins in synchronous pipelines |
| Input Noise Immunity | 28% VCC (min) - rejects noise spikes on control lines in electrically noisy environments |
| CARRY Output Logic | TE × QA × QB × QC × QD - enables seamless cascading of multiple counters for wider bit-width counting |
Pinout & Package
74AC161MTR is supplied in a 16-pin SOP (Small Outline Package) with 1.27 mm pitch, JEDEC MS-012 compliant, body dimensions 9.8 × 5.8 mm, and gull-wing leads.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (CLEAR) | Asynchronous Master Reset | Forces all outputs QA–QD LOW regardless of clock or enable state |
| 2 (CLOCK) | Rising-Edge Trigger Input | Counts or loads on each LOW→HIGH transition; synchronizes all internal flip-flops |
| 3–6 (A–D) | Parallel Data Inputs | Load preset value into counter on next clock edge when LOAD = LOW |
| 7 (PE) | Count Enable (Primary) | Must be HIGH with TE HIGH to permit counting; LOW inhibits count |
| 9 (LOAD) | Parallel Load Enable | LOW enables synchronous loading of A–D data on next clock edge |
| 10 (TE) | Carry Enable / Cascade Input | Enables CARRY OUT generation and controls cascade chaining with upstream counters |
| 11–14 (QA–QD) | 4-Bit Binary Counter Outputs | State outputs (LSB to MSB); QA toggles on every clock, QD changes every 16 clocks |
| 15 (CARRY OUT) | Terminal Count Signal | HIGH only when counter = 15 (1111) AND TE = HIGH - used for ripple-carry chaining |
| 8 (GND) | Ground Reference | 0V return path for all internal logic and I/O; requires low-impedance PCB connection |
| 16 (VCC) | Positive Supply | Power rail for entire device; decoupling capacitor (0.1 µF) required near pin |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous Preset + Asynchronous Clear | Enables deterministic initialization and mid-cycle reload without clock dependency |
| Balanced Propagation Delays (tPLH ≅ tPHL) | Minimizes duty cycle distortion in clock-derived waveforms for reliable downstream sampling |
| 50Ω Transmission Line Driving | Eliminates need for external series termination resistors in high-speed interconnects |
| 2kV HBM ESD Protection | Reduces risk of field failure during handling or operation in unshielded industrial enclosures |
| Wide Operating Voltage (2V–6V) | Permits direct interface with both 3.3V microcontrollers and legacy 5V TTL systems |
Applications
| Industrial PLC Timing Modules | Digital Panel Meter Address Sequencing |
|---|---|
Use Scenario: Generating precise time bases for scan cycles and watchdog timeouts in programmable logic controllers. IC Role / Device Role / Timing Role: Synchronous 4-bit counter providing stable, glitch-free clock division and event gating signals. Use Value: 125MHz max clock and balanced delays ensure sub-microsecond timing resolution across temperature ranges. | Use Scenario: Stepping through multi-digit LED display segments and ADC channel selections in portable meters. IC Role / Device Role / Timing Role: Parallel-load counter generating sequential address codes synchronized to system clock. Use Value: Pin-compatible 74-series replacement allows drop-in upgrade of legacy designs with lower power and higher speed. |
| Test Equipment Pulse Generators | Legacy Bus Interface Controllers |
Use Scenario: Creating programmable delay intervals and trigger patterns in automated test fixtures. IC Role / Device Role / Timing Role: Cascadable counter generating precise multi-cycle timing windows via CARRY OUT chaining. Use Value: TE-controlled CARRY OUT enables modular expansion to 8-, 12-, or 16-bit timing without redesign. | Use Scenario: Managing handshake timing and address decoding in ISA or proprietary parallel bus interfaces. IC Role / Device Role / Timing Role: Synchronous counter generating strobe and select signals aligned to bus clock edges. Use Value: 2V–6V operation supports direct integration with both 3.3V FPGAs and 5V bus transceivers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous counter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AC161N | DIP-16 package; higher ICC (160 µA max at -55°C to 125°C); identical AC/DC specs | Preferred for through-hole prototyping or legacy board rework where SOP reflow is unavailable | Select when manual soldering or socket-based testing is required |
| 74HC161PW | TSSOP-16; slower fMAX (44 MHz typ. at 4.5V); lower drive (±5.2 mA) | Suitable for low-speed, low-power battery-operated devices where 125MHz capability is unnecessary | Choose for cost-sensitive, non-timing-critical applications with relaxed speed requirements |
Compared with SN74AC161N and 74HC161PW, the 74AC161MTR delivers optimal balance of speed (125MHz), drive strength (24mA), and surface-mount reliability in industrial-grade SOP packaging - making it preferred for production-grade timing-critical embedded systems.
Availability
74AC161MTR is available at Aetrix Electronics and suitable for industrial PLC timing modules, digital panel meter address sequencing, and test equipment pulse generators requiring stable component supply and long-term lifecycle support.
Supply support for 74AC161MTR 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, MCU, power, and discrete components for industrial, automotive, and consumer markets.
The 74AC logic family was engineered for high-speed, low-power, and robust noise immunity in industrial control and instrumentation - targeting applications demanding reliable TTL-compatible performance beyond commercial temperature ranges.
FAQ
What is the function of the TE pin on the 74AC161MTR?
The TE (Terminal Count Enable) pin controls whether the CARRY OUT signal is generated. When TE is HIGH and the counter reaches state 15 (1111), CARRY OUT goes HIGH - enabling cascade chaining. When TE is LOW, CARRY OUT remains LOW regardless of counter state, effectively disabling ripple carry functionality.
Can the 74AC161MTR operate reliably at 3.3V supply?
Yes - the 74AC161MTR is fully specified from 2V to 6V, including 3.3V operation. At VCC = 3.3V, it delivers 70MHz typical maximum clock frequency, 2.1V VIH minimum, and maintains full 24mA output drive capability, making it compatible with mixed-voltage 3.3V/5V system designs.
How does the asynchronous CLEAR interact with synchronous LOAD?
CLEAR has absolute priority: when asserted LOW, it forces QA–QD to LOW immediately, overriding any pending LOAD operation or clock edge. LOAD only takes effect on the next rising clock edge if CLEAR is HIGH and LOAD is LOW - ensuring deterministic reset behavior independent of clock timing.
Is the 74AC161MTR RoHS compliant and lead-free?
Yes - the 74AC161MTR (SOP-16 package) is manufactured per RoHS Directive 2011/65/EU and is lead-free, with matte tin (Sn) lead finish. STMicroelectronics confirms compliance in its official product change notices and material declarations dated July 2001 onward.
74AC161MTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- 74AC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Logic Type:
- Binary Counter
- Direction:
- Up
- Number of Elements:
- 1
- Number of Bits per Element:
- 4
- Reset:
- Asynchronous
- Timing:
- Synchronous
- Count Rate:
- 125 MHz
- Trigger Type:
- Positive Edge
- Voltage - Supply:
- 2 V ~ 6 V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
74AC161MTR FAQ
1.How can I place an order for 74AC161MTR through Aetrix?
Please submit a Request for Quotation (RFQ) for 74AC161MTR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for 74AC161MTR reliable?
The price and inventory of 74AC161MTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74AC161MTR is usually 5 days.
3.What payment methods are accepted for 74AC161MTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74AC161MTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74AC161MTR?
74AC161MTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74AC161MTR order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for 74AC161MTR?
For technical support, including 74AC161MTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74AC161MTR requirements.
6.How does Aetrix verify that 74AC161MTR is sourced from the original manufacturer or authorized distributors?
All 74AC161MTR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that 74AC161MTR meets industry standards.
7.What is the process for return or replacement of 74AC161MTR?
All 74AC161MTR units undergo pre-shipment inspection (PSI). If there is an issue with 74AC161MTR, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The 74AC161MTR part is unused and in its original packaging.
Return procedure for 74AC161MTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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