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NXP Semiconductors 74HCT123D/AUJ
- Part No.:
- 74HCT123D/AUJ
- Manufacturer:
- NXP Semiconductors
- Category:
- Multivibrators
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
74HCT123D/AUJ.pdf
- Description:
- IC MULTIVIBRATOR 26NS 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,951
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Product details
Overview
74HCT123D/AUJ from Nexperia is a dual retriggerable monostable multivibrator with independent reset inputs, designed for precise pulse generation and timing control in digital systems. It operates from 4.5 V to 5.5 V, delivers propagation delays as low as 23 ns at 5 V, supports external timing components (REXT up to 1000 kΩ, CEXT up to 100 nF), and features Schmitt-trigger inputs on A/B pins for noise immunity-used in debounce circuits, event stretching, and programmable delay generators.
For engineers reviewing the 74HCT123D/AUJ datasheet, 74HCT123D/AUJ pinout, 74HCT123D/AUJ application, or 74HCT123D/AUJ equivalent, key selection considerations include TTL-compatible input thresholds (VIH = 2.0 V min, VIL = 0.8 V max), dual independent monostables with retriggerable output pulses up to 100% duty factor, direct asynchronous reset capability, and SO16 package compatibility with industrial temperature range (-40 °C to +125 °C).
Technical Context
The 74HCT123D/AUJ implements two independent edge-triggered monostable circuits, each with separate negative-edge (nA) and positive-edge (nB) trigger inputs, active-low direct reset (nRD), and complementary outputs (nQ, nQ). Pulse width is externally set via REXT and CEXT on pins nREXT/CEXT and nCEXT, with typical tW = 450 μs at REXT = 10 kΩ and CEXT = 100 nF.
Schmitt-trigger action on nA/nB inputs ensures robust operation with slow-rising signals, while clamp diodes enable safe interfacing to voltages beyond VCC using current-limiting resistors. The device complies with JEDEC JESD7A (2.0–6.0 V) and JESD8C (2.7–3.6 V), and exhibits latch-up immunity exceeding 100 mA per JESD78 Class II Level B.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - Ensures compatibility with standard 5 V TTL logic systems and stable operation across industrial voltage tolerances. |
| Propagation Delay | 23 ns (tPHL/tPLH, CL = 15 pF, VCC = 5 V) - Enables high-speed timing control in sub-25 ns critical paths. |
| Input Thresholds | VIH = 2.0 V min, VIL = 0.8 V max - Guarantees reliable recognition of standard TTL logic levels without level-shifting. |
| Timing Range | REXT = 2–1000 kΩ, CEXT = up to 100 nF - Supports pulse widths from ~75 ns to >1 ms, configurable per channel. |
| Operating Temperature | -40 °C to +125 °C - Validated for under-hood automotive, industrial PLC, and harsh-environment embedded applications. |
| Output Drive | ±4 mA (VOH/VOL at VCC = 4.5 V) - Sufficient to directly drive multiple 74-series inputs or small capacitive loads without buffering. |
| Power Dissipation | CPD = 56 pF per monostable - Enables accurate dynamic power estimation (PD = CPD × VCC² × fi + Σ(CL × VCC² × fo)) during system-level thermal analysis. |
Pinout & Package
74HCT123D/AUJ is housed in a plastic small outline package (SO16), SOT109-1, with 16 leads and 3.9 mm body width. Pin 1 is index-marked; pin 8 is GND; pin 16 is VCC.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A | Negative-edge triggered input 1 | Triggers monostable 1 on falling edge; enables precise event capture from open-collector or slow-decay signals. |
| 1B | Positive-edge triggered input 1 | Triggers monostable 1 on rising edge; used with clean clock or microcontroller GPIO outputs. |
| 1RD | Direct reset LOW input 1 | Asynchronously forces 1Q LOW and terminates ongoing pulse; no setup/hold required. |
| 1Q / 1Q | Complementary active-HIGH / active-LOW outputs 1 | Provides both logic polarities for driving different load types (e.g., 1Q to enable logic, 1Q to assert reset). |
| 1REXT/CEXT & 1CEXT | External timing node 1 | Connects to REXT and CEXT to set base pulse width; internal circuitry uses these to define tW = K × REXT × CEXT. |
| 2A / 2B / 2RD / 2Q / 2Q / 2REXT/CEXT / 2CEXT | Dual counterpart for monostable 2 | Functionally identical to channel 1, enabling independent timing control for two events (e.g., dual-channel sensor debouncing). |
| VCC (16) & GND (8) | Power supply terminals | Decoupling capacitor (100 nF ceramic) must be placed within 5 mm of pin 16 and pin 8 to suppress switching noise. |
Key Features
| Feature | Design Value |
|---|---|
| Retriggerable operation | Extends output pulse indefinitely by successive triggers-enables variable-duration strobes for motor run-time control or LED fade timing. |
| TTL-compatible inputs | Accepts standard 5 V TTL logic levels (VIH ≥ 2.0 V, VIL ≤ 0.8 V), eliminating need for level translators in mixed-logic systems. |
| Schmitt-trigger inputs on A/B | Provides hysteresis (typ. 0.5 V at VCC = 5 V), rejecting noise on mechanical switch inputs or long PCB traces without external RC filtering. |
| Independent reset per channel | Allows asynchronous termination of one monostable without affecting the other-critical for fault recovery in dual-sensor monitoring systems. |
| Wide temperature range | Specified from -40 °C to +125 °C ensures reliable timing accuracy in automotive engine control units and industrial motor drives. |
Applications
| Switch Debounce | Pulse Width Modulation (PWM) Edge Control |
|---|---|
Use Scenario: Mechanical push-button or rotary encoder interfaced to a microcontroller GPIO. IC Role / Device Role / Timing Role: Monostable 1 filters contact bounce by generating a clean, fixed-duration HIGH pulse on each press; Schmitt-trigger inputs reject EMI-induced glitches. Use Value: Eliminates software polling or timer-based debounce routines, reducing MCU firmware complexity and interrupt latency. | Use Scenario: Generating synchronized gate drive pulses for half-bridge MOSFETs in DC-DC converters. IC Role / Device Role / Timing Role: Monostable 1 shapes rising edge of PWM signal; monostable 2 shapes falling edge-creating precise dead-time insertion between high-side and low-side drivers. Use Value: Prevents shoot-through current without requiring dedicated PWM generator ICs or complex FPGA logic. |
| Event Stretching | Programmable Delay Generator |
Use Scenario: Extending short logic pulses from sensors (e.g., photointerrupter) to meet minimum enable duration requirements of downstream logic. IC Role / Device Role / Timing Role: Retriggerable monostable extends output pulse width each time a new trigger arrives-maintaining HIGH output as long as input events occur within trtrig window (110 ns min). Use Value: Converts burst-mode sensor output into sustained enable signal for analog-to-digital conversion windows or actuator hold periods. | Use Scenario: Introducing calibrated delays in test equipment or communication interface handshaking (e.g., UART RTS/CTS timing). IC Role / Device Role / Timing Role: Uses external REXT/CEXT to set precise delay (e.g., 100 μs to 10 ms); reset input allows early termination if handshake condition changes before timeout. Use Value: Provides hardware-level timing independence from processor clock jitter or OS scheduling delays-improving system determinism. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar monostable multivibrator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 74HC123D | CMOS-level inputs (VIH = 3.15 V min at VCC = 4.5 V), wider supply range (2.0–6.0 V), higher propagation delay (30 ns typ at 5 V). | Requires level translation when driven by TTL sources; better suited for mixed-voltage systems with 3.3 V or 2.5 V logic domains. | Select 74HC123D only when interfacing to CMOS logic families or operating below 4.5 V supply. |
| SN74LV123AD | Lower voltage operation (2.0–5.5 V), LV-CMOS inputs (VIH = 1.7 V min), faster tpd = 19 ns (VCC = 5 V), but no Schmitt-trigger inputs on A/B pins. | Lacks inherent noise immunity on trigger inputs-requires external RC filtering for switch debounce; optimized for speed-critical 3.3 V systems. | Choose SN74LV123AD when maximum speed and 3.3 V compatibility are prioritized over built-in Schmitt-trigger robustness. |
Compared with 74HC123D and SN74LV123AD, the 74HCT123D/AUJ uniquely combines TTL-level compatibility, Schmitt-trigger noise rejection, and industrial temperature support-making it optimal for legacy 5 V designs where reliability under EMI and mechanical noise is critical.
Availability
74HCT123D/AUJ is available at Aetrix Electronics and suitable for industrial control systems, automotive body electronics, test instrumentation, and embedded timing modules requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for 74HCT123D/AUJ 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
Nexperia is a global semiconductor expert delivering high-performance, reliable discrete, logic, and MOSFET solutions with focus on efficiency and sustainability.
The 74HCT123D/AUJ belongs to Nexperia's 74HCT logic family, engineered for seamless integration with legacy TTL systems while delivering CMOS power efficiency and robust industrial-grade performance.
FAQ
What is the recommended power supply decoupling for 74HCT123D/AUJ?
Place a 100 nF ceramic capacitor between VCC (pin 16) and GND (pin 8), located within 5 mm of the package. For systems with high-frequency switching or shared power rails, add a 10 μF tantalum or aluminum electrolytic capacitor near the board's main 5 V rail. This prevents supply droop during simultaneous output transitions and maintains stable VIH/VIL margins.
Can 74HCT123D/AUJ generate asymmetric pulse widths on the same channel?
Yes-the 74HCT123D/AUJ supports asymmetric pulse shaping via retriggering: an initial trigger sets the base pulse width (tW), and subsequent triggers on nA or nB extend the HIGH period of nQ. The LOW period remains fixed unless reset by nRD. This enables variable-duty-cycle generation without external counters or microcontrollers.
Does 74HCT123D/AUJ require external pull-up or pull-down resistors on its inputs?
No-74HCT123D/AUJ inputs have no internal pull resistors and must be actively driven. Floating nA, nB, or nRD pins may cause erratic triggering or increased ICC due to input leakage. Use microcontroller GPIOs, logic gates, or switches with defined HIGH/LOW states; avoid unterminated traces longer than 2 cm to prevent noise coupling.
How does the Schmitt-trigger action benefit 74HCT123D/AUJ in switch debounce applications?
The Schmitt-trigger inputs on nA and nB provide hysteresis (~0.5 V at VCC = 5 V), meaning the threshold for detecting a rising edge (~1.5 V) differs from that for a falling edge (~1.0 V). This prevents multiple false triggers during slow, noisy switch transitions-eliminating the need for external RC filters and ensuring single, clean output pulses per mechanical actuation.
What is the maximum safe value for CEXT when using 74HCT123D/AUJ at 5 V?
The datasheet specifies CEXT up to 100 nF for reliable operation at VCC = 5.0 V. Larger values increase pulse width but also raise risk of power-down damage due to stored energy discharge through input protection diodes. If CEXT > 10 nF, use the damping diode (DEXT) circuit shown in Figure 13 to protect against rapid VCC collapse during system shutdown.
74HCT123D/AUJ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- NXP Semiconductors
- Series:
- 74HCT
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Logic Type:
- Monostable
- Independent Circuits:
- 2
- Schmitt Trigger Input:
- Yes
- Propagation Delay:
- 26 ns
- Current - Output High, Low:
- 4mA, 4mA
- Voltage - Supply:
- 4.5 V ~ 5.5 V
- Operating Temperature:
- -40°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
74HCT123D/AUJ FAQ
1.How can I place an order for 74HCT123D/AUJ through Aetrix?
Please submit a Request for Quotation (RFQ) for 74HCT123D/AUJ 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 74HCT123D/AUJ reliable?
The price and inventory of 74HCT123D/AUJ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74HCT123D/AUJ is usually 5 days.
3.What payment methods are accepted for 74HCT123D/AUJ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74HCT123D/AUJ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74HCT123D/AUJ?
74HCT123D/AUJ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74HCT123D/AUJ 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 74HCT123D/AUJ?
For technical support, including 74HCT123D/AUJ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74HCT123D/AUJ requirements.
6.How does Aetrix verify that 74HCT123D/AUJ is sourced from the original manufacturer or authorized distributors?
All 74HCT123D/AUJ 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 74HCT123D/AUJ meets industry standards.
7.What is the process for return or replacement of 74HCT123D/AUJ?
All 74HCT123D/AUJ units undergo pre-shipment inspection (PSI). If there is an issue with 74HCT123D/AUJ, 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 74HCT123D/AUJ part is unused and in its original packaging.
Return procedure for 74HCT123D/AUJ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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