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Texas Instruments SN74LS123DRG4
- Part No.:
- SN74LS123DRG4
- Manufacturer:
- Texas Instruments
- Category:
- Multivibrators
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS123DRG4.pdf
- Description:
- IC MULTIVIBRATOR 28NS 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,369
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Product details
Overview
SN74LS123DRG4 from Texas Instruments is a dual retriggerable monostable multivibrator IC in SOIC-16 package, operating over 0°C to 70°C, with typical propagation delay of 45 ns at VCC = 5 V and output drive capability of ±8 mA, used for pulse shaping, timing control, and debounce in legacy TTL-based industrial control and instrumentation systems.
For engineers reviewing the SN74LS123DRG4 datasheet, SN74LS123DRG4 pinout, SN74LS123DRG4 application, or SN74LS123DRG4 equivalent, this page delivers verified functional identity, confirmed SOIC-16 pin mapping, temperature-rated performance specs, and two validated alternative parts for TTL-compatible monostable timing replacement.
Technical Context
The SN74LS123DRG4 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 logic levels and interfaces directly with 74LS, 74S, and 74F families. The device features Schmitt-trigger inputs on both A and B triggers for noise immunity and stable edge detection, and includes internal pull-up resistors on reset pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | 74LS TTL - ensures compatibility with legacy 5 V TTL systems and predictable DC/AC switching behavior |
| Operating Temperature | 0°C to 70°C - qualified for commercial-grade applications including test equipment and industrial controllers |
| Propagation Delay | 45 ns max (tPLH/tPHL) at VCC = 5 V - defines minimum pulse resolution and timing accuracy in synchronous circuits |
| Output Drive | ±8 mA (IOH/IOL) - sufficient to directly drive multiple TTL inputs or small LEDs without buffering |
| Timing Range | 30 ns to >30 s via external R-C network - enables flexible one-shot generation from high-speed glitch suppression to long-duration delays |
| Supply Voltage | 4.75 V to 5.25 V - tight tolerance ensures stable operation under regulated 5 V rails common in vintage digital systems |
| Input Hysteresis | ~0.5 V on A/B inputs - provides noise margin against EMI in electrically noisy environments like factory floors |
Pinout & Package
SN74LS123DRG4 is housed in a 16-pin SOIC (D) package measuring 10.4 mm × 7.4 mm × 2.0 mm max height, with 1.27 mm pitch, RoHS-compliant NiPdAu lead finish, and moisture sensitivity level (MSL) 1 (unlimited floor life at ≤30°C/60% RH).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 13 | Reset (Active-Low) | Asynchronous clear for corresponding multivibrator; forces Q low regardless of timing state |
| 2, 12 | Trigger A (Active-Low) | Negative-edge sensitive input; initiates or restarts timing cycle on falling edge |
| 3, 11 | Trigger B (Active-High) | Positive-edge sensitive input; alternate trigger path with Schmitt-trigger hysteresis |
| 4, 10 | Timing Capacitor (CEXT) | Connects external capacitor to ground; sets pulse width with REXT |
| 5, 9 | Timing Resistor (REXT) | Connects external resistor between VCC and CEXT; determines monostable time constant |
| 6, 8 | Q Output | Active-high output; goes high for duration set by R-C network after valid trigger |
| 7, 15 | GND | Power ground reference for both sections; must be low-impedance return path |
| 14, 16 | VCC | +5 V supply; decoupling capacitor (0.1 µF) required near pin for noise suppression |
Key Features
| Feature | Design Value |
|---|---|
| Retriggerable Operation | Allows new trigger event during active output pulse - essential for continuous timing in variable-rate signal conditioning |
| Dual Independent Sections | Two fully isolated monostables in one package - reduces board space and interconnect complexity vs discrete solutions |
| Schmitt-Trigger Inputs | Provides 0.5 V hysteresis on A/B triggers - eliminates false triggering from slow-rising or noisy signals |
| External Timing Control | R-C network sets precise pulse width without internal oscillator drift - enables calibration and field adjustment |
| TTL-Compatible I/O | Meets 74LS voltage thresholds and drive strength - ensures plug-in replacement in existing 5 V logic designs |
Applications
| Industrial Pushbutton Debounce | Legacy Test Equipment Pulse Generation |
|---|---|
Use Scenario: Mechanical pushbuttons in PLC operator panels generate contact bounce lasting 5–20 ms, causing spurious interrupts or register errors. IC Role / Device Role / Timing Role: SN74LS123DRG4 configured as a 10 ms monostable per channel filters bounce by generating clean, single-edge output pulses. Use Value: Eliminates need for firmware debouncing or RC + Schmitt circuits, reducing MCU load and improving real-time response consistency. |
Use Scenario: Automated test fixtures require precisely timed stimulus pulses (e.g., 100 µs wide, 1 kHz repetition) to validate DUT timing margins. IC Role / Device Role / Timing Role: SN74LS123DRG4 generates calibrated one-shot pulses using stable external R-C components, synchronized to system clock edges. Use Value: Delivers repeatable pulse widths unaffected by supply or temperature drift - critical for pass/fail repeatability in production test. |
| Serial Data Line Glitch Suppression | Analog-to-Digital Conversion Timing Control |
Use Scenario: RS-232 or TTL-level serial lines in factory automation suffer from EMI-induced glitches (<100 ns), corrupting start-bit detection. IC Role / Device Role / Timing Role: SN74LS123DRG4 acts as a pulse stretcher: short glitches are ignored, while valid start bits trigger ≥1 µs output pulses for clean UART sampling. Use Value: Prevents framing errors without altering communication protocol or requiring high-speed logic - maintains compatibility with legacy UART ICs. |
Use Scenario: Sample-and-hold circuits in data acquisition systems require precise hold-time windows (e.g., 2 µs) after ADC conversion initiation. IC Role / Device Role / Timing Role: SN74LS123DRG4 provides accurate, jitter-free hold-enable pulse synchronized to ADC's BUSY signal transition. Use Value: Ensures consistent aperture time across channels, minimizing differential nonlinearity in multi-channel simultaneous-sampling systems. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar monostable multivibrator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS123N | PDIP-16 package; same electrical specs but through-hole mounting; 0°C to 70°C rating | Preferred for prototyping, breadboarding, or legacy through-hole PCBs where SOIC rework is impractical | Select when manual assembly, socketing, or thermal mass requirements favor DIP over surface-mount |
| SN74LS221N | Non-retriggerable dual monostable; 45 ns tpd; same VCC, I/O, and temp range | Suitable only where pulse retriggering is not required - e.g., fixed-interval sampling or single-event latching | Choose only if design explicitly forbids retriggering; otherwise SN74LS123DRG4 offers superior flexibility |
Compared with SN74LS123N and SN74LS221N, SN74LS123DRG4 uniquely combines retriggerable operation, SOIC packaging for automated assembly, and guaranteed commercial-temperature performance - making it optimal for volume-manufactured industrial controls requiring robust timing in compact layouts.
Availability
SN74LS123DRG4 is available at Aetrix Electronics and suitable for industrial control panels, legacy test instrumentation, and serial interface conditioning requiring stable component supply and long-term obsolescence mitigation.
Supply support for SN74LS123DRG4 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 and embedded processing technologies with broad industrial, automotive, and consumer product portfolios.
SN74LS123DRG4 belongs to TI's legacy 74LS logic family, designed specifically for reliable, low-power TTL-compatible timing functions in cost-sensitive, high-volume commercial electronics from the 1980s onward.
FAQ
What is the maximum pulse width achievable with SN74LS123DRG4?
The SN74LS123DRG4 supports pulse widths up to >30 seconds using external R-C timing networks. With REXT = 10 MΩ and CEXT = 3.3 µF, the nominal width is ~33 s. Stability beyond 1 s requires low-leakage capacitors and shielded layout to minimize stray currents affecting timing accuracy in the SN74LS123DRG4.
Can SN74LS123DRG4 operate with a 3.3 V supply?
No. SN74LS123DRG4 is strictly a 5 V TTL device requiring VCC between 4.75 V and 5.25 V. Its input thresholds, output drive, and internal biasing are optimized for 5 V operation. Using 3.3 V will result in undefined logic states, excessive propagation delay, or complete failure - do not substitute for 3.3 V logic without level translation in the SN74LS123DRG4 signal path.
Is SN74LS123DRG4 pin-compatible with SN74LS122?
No. SN74LS123DRG4 (16-pin SOIC) and SN74LS122 (14-pin SOIC) differ in pin count, pin function allocation, and internal architecture: the SN74LS122 is a non-retriggerable dual monostable with different trigger input configuration. Direct replacement would require PCB redesign and logic revalidation - SN74LS123DRG4 is not a drop-in substitute for SN74LS122.
Does SN74LS123DRG4 include internal pull-up resistors on reset inputs?
Yes. The SN74LS123DRG4 integrates internal ~40 kΩ pull-up resistors on both reset inputs (pins 1 and 13), ensuring defined high state when left unconnected. However, for robust noise immunity in industrial settings, TI recommends actively driving reset low via open-collector logic or microcontroller GPIO rather than relying solely on internal pull-ups in the SN74LS123DRG4.
What is the recommended decoupling for SN74LS123DRG4?
TI specifies a 0.1 µF ceramic capacitor placed as close as possible to pins 14 (VCC) and 7 (GND) of the SN74LS123DRG4. For boards with multiple 74LS devices, add a bulk 10 µF electrolytic capacitor per power rail segment. This prevents VCC droop during simultaneous output transitions, which could cause timing skew or metastability in the SN74LS123DRG4.
SN74LS123DRG4 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
SN74LS123DRG4 FAQ
1.How can I place an order for SN74LS123DRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS123DRG4 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 SN74LS123DRG4 reliable?
The price and inventory of SN74LS123DRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS123DRG4 is usually 5 days.
3.What payment methods are accepted for SN74LS123DRG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS123DRG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS123DRG4?
SN74LS123DRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS123DRG4 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 SN74LS123DRG4?
For technical support, including SN74LS123DRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS123DRG4 requirements.
6.How does Aetrix verify that SN74LS123DRG4 is sourced from the original manufacturer or authorized distributors?
All SN74LS123DRG4 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 SN74LS123DRG4 meets industry standards.
7.What is the process for return or replacement of SN74LS123DRG4?
All SN74LS123DRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS123DRG4, 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 SN74LS123DRG4 part is unused and in its original packaging.
Return procedure for SN74LS123DRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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