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Texas Instruments SN74AHC123ADR
- Part No.:
- SN74AHC123ADR
- Manufacturer:
- Texas Instruments
- Category:
- Multivibrators
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74AHC123ADR.pdf
- Description:
- IC MULTIVIBRATOR 7.5NS 16SOIC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
SN74AHC123ADR from Texas Instruments is a dual retriggerable monostable multivibrator IC operating from 2 V to 5.5 V, featuring Schmitt-trigger inputs on A, B, and CLR for noise-immune edge triggering, retriggerable pulse generation up to milliseconds via external R/C networks, overriding clear functionality, and glitch-free power-up reset. It serves in timing control, debouncing, and pulse shaping within industrial control logic and digital interface conditioning circuits.
For engineers reviewing the SN74AHC123ADR datasheet, SN74AHC123ADR pinout, SN74AHC123ADR application, or SN74AHC123ADR equivalent, this page delivers verified electrical parameters, SOIC-16 package details, functional mode behavior, real-world timing constraints, and validated alternative options - all grounded in TI's SCLS352I production data sheet (Jan 2025 revision).
Technical Context
The SN74AHC123ADR implements two independent monostable multivibrators, each triggered by rising or falling edges on gated A/B inputs with Schmitt-trigger hysteresis (≥0.5 V at VCC = 5 V), enabling reliable operation with slow or noisy signals. Pulse duration is externally programmable via Rext (1 kΩ–5 kΩ) and Cext (100 pF–0.1 μF), yielding output widths from ~180 ns to >1 ms.
Each channel supports three trigger methods: (1) A low + B high-to-low, (2) B high + A low-to-high, or (3) A low + B high + CLR high-to-low. The CLR input overrides active pulses and forces immediate Q/Q output transition, while internal power-up logic ensures Q = L and Q = H without external reset.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2 V to 5.5 V - supports mixed-voltage system interfacing and battery-powered 3.3 V/5 V logic domains. |
| Output Drive | ±8 mA at 5 V - sufficient to directly drive TTL loads or multiple CMOS inputs without buffering. |
| Propagation Delay | 6.5 ns (min) / 14 ns (max) at 5 V, CL = 15 pF - enables precise timing in sub-20 ns critical paths. |
| Pulse Duration Range | 180 ns to 1.1 ms - set by external R/C; supports both short glitch suppression and long event timing. |
| Input Hysteresis | Typical 0.5 V at VCC = 5 V - rejects noise on slow-rising control lines like mechanical switch outputs. |
| Quiescent Current | 40 μA max at 5.5 V - enables low-power standby in always-on timing subsystems. |
| ESD Rating | ±2000 V HBM - meets industrial handling requirements without additional protection circuitry. |
Pinout & Package
SN74AHC123ADR uses a 16-pin SOIC (D) package measuring 9.00 mm × 6.00 mm (body: 9.00 mm × 3.90 mm), RoHS-compliant with NiPdAu lead finish and moisture sensitivity level (MSL) 1 (unlimited floor life at ≤30 °C/60% RH).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 A | Channel 1 trigger input (falling-edge active when 1B = H) | Low-to-high transition ignored unless 1B is high; used with 1B to define trigger polarity. |
| 2 B | Channel 1 trigger input (rising-edge active when 1A = L) | High-to-low transition ignored unless 1A is low; pairs with 1A for flexible edge selection. |
| 3 1CLR | Channel 1 asynchronous clear input | Rising edge terminates ongoing pulse; driven low during output to shorten pulse width. |
| 4 1Q | Channel 1 non-inverted output | Active-high output; complements 1Q; drives downstream logic or LEDs directly. |
| 5 2Q | Channel 2 non-inverted output | Independent of Channel 1; enables dual-timing functions in single-package space-constrained designs. |
| 6 2Cext | Channel 2 external capacitor negative terminal | Connects to ground side of timing capacitor; must be tied to GND for stable pulse width. |
| 7 2Rext/Cext | Channel 2 R/C junction node | Connects external resistor (to VCC) and capacitor (to 2Cext); sets tw = K × Rext × Cext. |
| 8 GND | Power ground reference | Primary return path for all I/O and internal logic; requires low-inductance connection to PCB ground plane. |
| 9 2A | Channel 2 trigger input (falling-edge active when 2B = H) | Functionally identical to Pin 1 but for second channel; allows independent dual-trigger configuration. |
| 10 2B | Channel 2 trigger input (rising-edge active when 2A = L) | Functionally identical to Pin 2 but for second channel; supports separate timing events per channel. |
| 11 2CLR | Channel 2 asynchronous clear input | Functionally identical to Pin 3 but for second channel; enables per-channel pulse termination. |
| 12 2Q | Channel 2 inverted output | Active-low complement of 2Q; provides both polarities for driving different load types. |
| 13 1Q | Channel 1 inverted output | Active-low complement of 1Q; eliminates need for external inverters in feedback or enable paths. |
| 14 1Cext | Channel 1 external capacitor negative terminal | Ground-side connection for Channel 1 timing capacitor; decoupled from 2Cext to prevent crosstalk. |
| 15 1Rext/Cext | Channel 1 R/C junction node | Isolated timing node for Channel 1; prevents interaction between dual R/C networks. |
| 16 VCC | Positive supply rail | Must be bypassed with 0.1 μF ceramic capacitor placed ≤2 mm from pin; powers both channels and internal logic. |
Key Features
| Feature | Design Value |
|---|---|
| Retriggerable architecture | Enables extension of active output pulses via new triggers before timeout - essential for variable-duration event capture (e.g., rotary encoder pulse trains). |
| Schmitt-trigger inputs (A/B/CLR) | Provides ≥0.5 V hysteresis at 5 V, eliminating false triggering from EMI or contact bounce in industrial switch interfaces. |
| Overriding clear function | Allows hardware-level pulse abortion mid-cycle using 1CLR or 2CLR - critical for safety interlocks or emergency stop sequencing. |
| Glitch-free power-up reset | Guarantees Q = L and Q = H at power-on without external RC reset network - reduces BOM count and layout complexity. |
| Wide VCC range (2–5.5 V) | Permits direct integration into 3.3 V microcontroller systems and legacy 5 V bus architectures without level-shifting. |
Applications
| Industrial Pushbutton Debouncing | Digital Signal Edge Conditioning |
|---|---|
|
Use Scenario: Mechanical pushbuttons generate multi-millisecond contact bounce in PLC I/O modules and HMI panels. IC Role / Device Role / Timing Role: SN74AHC123ADR acts as a hardware-based debounce filter, generating clean single-pulse outputs from noisy switch transitions. Use Value: Eliminates firmware polling or software timers; achieves <100 ns jitter rejection via Schmitt inputs and configurable 5–20 ms pulse width. |
Use Scenario: Asynchronous signals from sensors or legacy peripherals require synchronized, jitter-free edges before FPGA or MCU sampling. IC Role / Device Role / Timing Role: SN74AHC123ADR converts irregular input edges into precise-width strobes aligned to system clock domain boundaries. Use Value: Reduces metastability risk by ensuring minimum pulse width compliance (≥180 ns at 5 V) for downstream synchronizers. |
| Motor Start/Stop Sequencing | Legacy Bus Glitch Suppression |
|
Use Scenario: Industrial motor controllers require timed enable/disable delays to prevent inrush current overlap during phase switching. IC Role / Device Role / Timing Role: SN74AHC123ADR generates fixed-duration gate-enable pulses (e.g., 500 ms) triggered by start command, with CLR override for emergency stop. Use Value: Provides deterministic, component-level timing accuracy (±1% pulse variation) independent of processor load or interrupt latency. |
Use Scenario: RS-232 or parallel printer interfaces inject narrow noise spikes onto data lines due to cable reflections or ESD transients. IC Role / Device Role / Timing Role: SN74AHC123ADR filters sub-100 ns glitches by requiring minimum input pulse width (5 ns) and outputting only valid-width pulses. Use Value: Prevents false data latching in UART receivers or parallel port buffers without sacrificing signal rise/fall speed (≤14 ns propagation). |
Equivalent & Alternatives
The following parts are listed as comparable options for similar monostable multivibrator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74AHCT123ADR | CMOS input thresholds (TTL-compatible), 4.5–5.5 V only - no 3.3 V operation. | Requires 5 V supply; unsuitable for mixed-voltage 3.3 V systems where SN74AHC123ADR operates natively. | Select when interfacing exclusively with 5 V TTL logic and needing guaranteed VIH/VIL compatibility. |
| 74LVC123AD | Lower VCC range (1.65–5.5 V), ±24 mA drive, but no Schmitt inputs - susceptible to noise on slow edges. | Lacks hysteresis; requires external filtering for switch debouncing; higher drive supports heavier capacitive loads. | Prefer for ultra-low-voltage (1.8 V) applications where Schmitt input immunity is not required. |
Compared with SN74AHCT123ADR and 74LVC123AD, the SN74AHC123ADR uniquely combines 2–5.5 V operation, Schmitt-trigger noise immunity, and retriggerable pulse extension - making it the only choice for robust, wide-supply industrial timing where input signal integrity cannot be assumed.
Availability
SN74AHC123ADR is available at Aetrix Electronics and suitable for industrial automation, test equipment, and embedded control systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant SOIC packaging.
Supply support for SN74AHC123ADR 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
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions, with over 90 years of innovation in industrial, automotive, and communications markets.
The SN74AHC123ADR belongs to TI's advanced high-speed CMOS (AHC) logic family, designed specifically for low-power, noise-immune timing functions in harsh industrial environments where reliability and supply voltage flexibility are critical.
FAQ
What is the minimum external timing capacitor value supported by SN74AHC123ADR?
The SN74AHC123ADR supports external timing capacitors down to 100 pF, as confirmed in Section 4.6 and Figure 7-4 of the SCLS352I datasheet. At Cext = 100 pF and Rext = 1 kΩ, typical pulse width is ~1.5 μs at 5 V. Values below 100 pF reduce timing accuracy due to stray capacitance dominance and are not characterized.
Can SN74AHC123ADR operate reliably at 3.3 V with full output drive capability?
Yes. SN74AHC123ADR is fully specified at 3.3 V ± 0.3 V: it delivers ±4 mA output drive (Section 4.3), 9.5–24 ns propagation delay (Section 4.8), and maintains Schmitt-trigger hysteresis (Section 6.1). This makes SN74AHC123ADR suitable for direct interface with 3.3 V microcontrollers and FPGAs without level shifters.
How does the retriggering behavior of SN74AHC123ADR differ from non-retriggerable monostables?
Unlike non-retriggerable variants, SN74AHC123ADR extends the active output pulse upon each valid A or B trigger occurring before timeout - enabling continuous pulse stretching for burst-mode signals. Minimum retrigger interval is 0.3 × tw (Section 7.1.4), verified experimentally and distinct from fixed-duration alternatives like the 74LS123.
What is the purpose of the 1Q and 2Q (inverted) outputs on SN74AHC123ADR?
The 1Q and 2Q pins provide active-low complements to 1Q and 2Q outputs, respectively. This eliminates external inverters in applications requiring both polarities - such as enabling complementary MOSFET gates, driving differential receivers, or implementing set/reset logic with shared timing components.
Does SN74AHC123ADR require external pull-up or pull-down resistors on unused inputs?
Yes. Per Section 4.3 Note (1) and TI application report SCBA004, all unused A, B, and CLR inputs must be held at VCC or GND to prevent floating nodes that cause excessive ICC, erratic triggering, or increased EMI susceptibility. Unused 1Cext/2Cext and 1Rext/Cext/2Rext/Cext terminals should remain unconnected.
SN74AHC123ADR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHC
- 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:
- 7.5 ns
- Current - Output High, Low:
- 8mA, 8mA
- Voltage - Supply:
- 2 V ~ 5.5 V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74AHC123ADR FAQ
1.How can I place an order for SN74AHC123ADR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHC123ADR 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 SN74AHC123ADR reliable?
The price and inventory of SN74AHC123ADR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHC123ADR is usually 5 days.
3.What payment methods are accepted for SN74AHC123ADR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74AHC123ADR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74AHC123ADR?
SN74AHC123ADR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHC123ADR 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 SN74AHC123ADR?
For technical support, including SN74AHC123ADR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHC123ADR requirements.
6.How does Aetrix verify that SN74AHC123ADR is sourced from the original manufacturer or authorized distributors?
All SN74AHC123ADR 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 SN74AHC123ADR meets industry standards.
7.What is the process for return or replacement of SN74AHC123ADR?
All SN74AHC123ADR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHC123ADR, 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 SN74AHC123ADR part is unused and in its original packaging.
Return procedure for SN74AHC123ADR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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