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Texas Instruments SN74LS123DRE4
- Part No.:
- SN74LS123DRE4
- Manufacturer:
- Texas Instruments
- Category:
- Multivibrators
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS123DRE4.pdf
- Description:
- IC MULTIVIBRATOR 28NS 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,953
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Product details
Overview
SN74LS123DRE4 from Texas Instruments is a dual retriggerable monostable multivibrator IC in 16-pin SOIC package, operating over 0°C to 70°C, with typical propagation delay of 25 ns at VCC = 5 V and CL = 15 pF, and output drive capability of ±8 mA, used for pulse shaping, timing control, and debounce in legacy TTL-based industrial control logic.
For engineers reviewing the SN74LS123DRE4 datasheet, SN74LS123DRE4 pinout, SN74LS123DRE4 application, or SN74LS123DRE4 equivalent, this page delivers verified functional identity, confirmed SOIC-16 pin mapping, exact timing parameter ranges per SDLS043, and two validated alternative parts for TTL-compatible monostable replacement scenarios.
Technical Context
The SN74LS123DRE4 contains two independent retriggerable monostable multivibrators, each with separate A and B trigger inputs (active-low and active-high), reset input (active-low), and Q/Q̅ complementary outputs. Each section supports external RC timing networks with adjustable pulse width from 30 ns to 30 s.
It uses standard TTL circuitry with Schottky-clamped transistors, ensuring compatibility with 74LS family logic levels and fan-out of 20 LS-TTL loads. The device does not require external pull-ups on trigger inputs and features internal clamping diodes for transient protection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Function | Dual retriggerable monostable multivibrator - enables precise one-shot pulse generation that can be extended mid-cycle by new triggers. |
| Supply Voltage | 4.75 V to 5.25 V - matches standard TTL rail; operation outside this range risks invalid output states or latch-up. |
| Pulse Width Range | 30 ns to 30 s - set externally via R×C network; minimum width limited by internal propagation delay. |
| Propagation Delay | 25 ns typical (VCC = 5 V, CL = 15 pF) - defines minimum achievable pulse resolution and system timing margin. |
| Output Drive | ±8 mA (IOH/ IOL) - sufficient to directly drive LS-TTL inputs or small LEDs without buffering. |
| Operating Temperature | 0°C to 70°C - commercial-grade rating; not qualified for extended industrial or automotive temperature ranges. |
| Package | SOIC-16 (D package) - 3.9 mm body width, 1.75 mm max height, 1.27 mm pitch; compatible with standard surface-mount assembly. |
Pinout & Package
SN74LS123DRE4 is housed in a 16-pin Small Outline Integrated Circuit (SOIC) package with 1.27 mm lead pitch and JEDEC MS-012AB compliance. Pin 1 is located at the top-left corner adjacent to the index notch or dot marking.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1A, 1B | Section 1 trigger inputs | 1A active-low, 1B active-high - dual-edge triggering allows flexible edge-sensitivity configuration per section. |
| 1R̅ | Section 1 reset | Active-low asynchronous reset - forces Q1 low and terminates current output pulse immediately. |
| 1Q, 1Q̅ | Section 1 outputs | Complementary TTL-level outputs - Q1 high during monostable pulse; Q̅1 inverted. |
| 2A, 2B | Section 2 trigger inputs | Independent dual-edge trigger inputs identical in function to 1A/1B. |
| 2R̅ | Section 2 reset | Asynchronous reset for second section only; no cross-section coupling. |
| 2Q, 2Q̅ | Section 2 outputs | Complementary outputs isolated from Section 1; supports concurrent independent timing operations. |
| VCC, GND | Power terminals | VCC on Pin 16, GND on Pin 8 - standard dual-supply placement for SOIC-16; decoupling capacitor required near VCC. |
Key Features
| Feature | Design Value |
|---|---|
| Retriggerable operation | Allows extending output pulse duration dynamically during active state - critical for variable-debounce or gated timing applications. |
| No external components required for basic operation | Internal timing resistors enable fixed-width operation; external RC network optional for precision adjustment. |
| TTL-compatible input thresholds | VIL ≤ 0.8 V, VIH ≥ 2.0 V - ensures reliable interfacing with 74LS, 74S, and standard 5 V CMOS logic families. |
| Complementary outputs | Q and Q̅ available per section - eliminates need for external inverters in edge-detection or differential signaling paths. |
| Reset independence | Each section has dedicated active-low reset - enables selective termination without affecting parallel timing channels. |
Applications
| Industrial Control Panel Debounce | Legacy System Timing Synchronization |
|---|---|
|
Use Scenario: Mechanical pushbutton inputs in PLC operator panels generate contact bounce lasting 5–20 ms, causing spurious logic transitions. IC Role / Device Role / Timing Role: SN74LS123DRE4 Section 1 configured as 15 ms monostable to suppress bounce; input tied to button, output feeds clean clock or enable signal. Use Value: Eliminates need for RC + Schmitt trigger discrete solution; TTL-compatible drive ensures direct interface with downstream 74LS counters or latches. |
Use Scenario: Synchronizing asynchronous status signals (e.g., fault flags from analog modules) to a central 1 MHz system clock domain. IC Role / Device Role / Timing Role: SN74LS123DRE4 used as pulse stretcher to extend narrow fault pulses to ≥100 ns, guaranteeing capture by clocked registers. Use Value: Provides deterministic minimum pulse width independent of source jitter; dual sections allow simultaneous handling of multiple fault lines. |
| Test Equipment Pulse Generation | Legacy Bus Arbitration Timing |
|
Use Scenario: Bench test fixtures require user-triggered, repeatable 100 µs strobe pulses for DUT stimulus under manual control. IC Role / Device Role / Timing Role: SN74LS123DRE4 Section 2 triggered manually via front-panel switch; RC network sets precise 100 µs width. Use Value: Delivers stable, jitter-free TTL pulses without microcontroller firmware overhead; retriggerability allows rapid successive pulses. |
Use Scenario: Arbitrating access to shared parallel bus in vintage computer backplanes where bus grant must persist ≥200 ns after request. IC Role / Device Role / Timing Role: SN74LS123DRE4 generates fixed 250 ns grant pulse upon bus request detection, overriding shorter native logic delays. Use Value: Guarantees minimum bus grant duration required by legacy peripherals; dual-section design supports master/slave arbitration logic. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar retriggerable monostable multivibrator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS123DR | Same die, identical electrical specs; differs only in tape-and-reel packaging (2500 pcs/reel vs. 40 pcs/tube for DRE4). | No functional difference; suitable for high-volume SMT production but requires reel-handling infrastructure. | Select SN74LS123DR for automated assembly; SN74LS123DRE4 preferred for prototyping or low-volume hand-soldered builds. |
| SN74LS221N | Non-retriggerable dual monostable; 45 ns typical propagation delay; requires external resistor for timing (no internal R option). | Cannot extend pulse mid-cycle; unsuitable for debounce with variable bounce duration or dynamic timing extension. | Choose SN74LS221N only when strict non-retriggerable behavior is required and pulse width is fixed per design. |
Compared with SN74LS123DR, SN74LS123DRE4 offers identical functionality in tube packaging for flexibility in low-volume use; versus SN74LS221N, it provides essential retriggerability and tighter propagation delay for responsive timing-critical systems.
Availability
SN74LS123DRE4 is available at Aetrix Electronics and suitable for industrial control panel debounce, legacy system timing synchronization, test equipment pulse generation, and legacy bus arbitration timing requiring stable component supply across long-lifecycle embedded programs.
Supply support for SN74LS123DRE4 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic products with broad industrial and automotive qualification.
SN74LS123DRE4 belongs to TI's legacy 74LS logic family, designed specifically for robust, low-power TTL-compatible timing and waveform generation in cost-sensitive, long-lifecycle industrial and instrumentation systems.
FAQ
What is the maximum recommended RC timing capacitance for SN74LS123DRE4?
The SN74LS123DRE4 datasheet specifies a maximum external timing capacitance of 1000 pF for stable operation. Exceeding this value increases susceptibility to noise-induced false triggering and degrades pulse width accuracy due to stray capacitance effects. For values above 1000 pF, the SN74LS123DRE4 may exhibit inconsistent timeout behavior or failure to trigger reliably. Always verify timing with actual board layout parasitics included.
Does SN74LS123DRE4 support Schmitt-trigger inputs for noisy environments?
No, the SN74LS123DRE4 does not incorporate Schmitt-trigger input circuitry. Its trigger inputs (1A, 1B, 2A, 2B) follow standard TTL thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) without hysteresis. In electrically noisy environments, external RC filtering or dedicated Schmitt buffers such as SN74LS14 should precede SN74LS123DRE4 inputs to prevent multiple triggering.
Can SN74LS123DRE4 operate with a 3.3 V supply?
No, SN74LS123DRE4 is specified only for 4.75 V to 5.25 V operation. Applying 3.3 V violates its absolute maximum ratings and results in undefined output states, increased propagation delay, and potential failure to recognize valid TTL input levels. For 3.3 V systems, consider modern alternatives like SN74LVC1G123 or level-shifting interfaces.
Is there an internal pull-up on the reset pin of SN74LS123DRE4?
No, SN74LS123DRE4 reset pins (1R̅ and 2R̅) have no internal pull-up. They are active-low, TTL-compatible inputs requiring explicit external pull-up to VCC (typically 4.7 kΩ) when not actively driven. Leaving them floating risks metastable or unintended reset assertion due to noise coupling.
How does retriggering affect the output pulse width of SN74LS123DRE4?
When a new trigger occurs during an active output pulse of SN74LS123DRE4, the monostable timer resets and begins a new full-width cycle from that instant. The output remains high for exactly the programmed RC time after the latest valid trigger, enabling dynamic pulse extension - a key distinction from non-retriggerable variants like SN74LS221N.
SN74LS123DRE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- Logic Type:
- Monostable
- Independent Circuits:
- 2
- Schmitt Trigger Input:
- No
- Propagation Delay:
- 28 ns
- Current - Output High, Low:
- 400µA, 8mA
- Voltage - Supply:
- 4.75 V ~ 5.25 V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SOIC
SN74LS123DRE4 FAQ
1.How can I place an order for SN74LS123DRE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS123DRE4 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 SN74LS123DRE4 reliable?
The price and inventory of SN74LS123DRE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS123DRE4 is usually 5 days.
3.What payment methods are accepted for SN74LS123DRE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS123DRE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS123DRE4?
SN74LS123DRE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS123DRE4 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 SN74LS123DRE4?
For technical support, including SN74LS123DRE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS123DRE4 requirements.
6.How does Aetrix verify that SN74LS123DRE4 is sourced from the original manufacturer or authorized distributors?
All SN74LS123DRE4 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 SN74LS123DRE4 meets industry standards.
7.What is the process for return or replacement of SN74LS123DRE4?
All SN74LS123DRE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS123DRE4, 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 SN74LS123DRE4 part is unused and in its original packaging.
Return procedure for SN74LS123DRE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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