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Home > Products > Integrated Circuits (ICs) > Logic > Multivibrators

Texas Instruments SN74LS123NS

Name: SN74LS123NS
Brand: Texas Instruments
SKU: SN74LS123NS
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LS123NS

Manufacturer:: Texas Instruments

Category:: Multivibrators

Package:: 16-SOIC (0.209", 5.30mm Width)

Datasheet:: SN74LS123NS.pdf

Description:: IC MULTIVIBRATOR 34NS 16SO

Quantity:: RFQ Add To RFQ list

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Product details

Overview

SN74LS123NS from Texas Instruments is a dual retriggerable monostable multivibrator IC in 16-pin SOP (NS) package, operating over 0°C to 70°C, with typical output pulse width of 11 ns at V_CC = 5 V and I_OL = 8 mA, used for precise timing control in digital logic interfacing and pulse shaping circuits.

For engineers reviewing the SN74LS123NS datasheet, SN74LS123NS pinout, SN74LS123NS application, or SN74LS123NS equivalent, this page delivers verified functional identity, confirmed SOP-16 pin mapping, temperature-rated performance data, and validated drop-in alternatives for legacy TTL timing design continuity.

Technical Context

The SN74LS123NS implements two independent retriggerable monostable multivibrators per package, each with separate A and B trigger inputs, clear (CLR) control, Q and Q̅ outputs, and external RC timing networks. Its LS-TTL input thresholds and output drive capability (I_OH = −0.4 mA, I_OL = 8 mA) ensure compatibility with standard 74LS logic families.

Each monostable supports both negative-edge triggering (via A input) and positive-edge triggering (via B input), with retriggering enabled during the output pulse period-allowing pulse extension without requiring full timeout completion before new triggers are accepted.

Key Specifications

Parameter	Value and Actual Design Meaning
Logic Family	74LS (Low-power Schottky TTL), compatible with standard TTL and CMOS inputs at V_CC = 5 V.
Operating Temperature	0°C to 70°C - suitable for commercial-grade industrial and instrumentation applications.
Package Type	SOP (NS) - 16-pin surface-mount small-outline package, 1.27 mm pitch, 2.00 mm max height.
Output Drive	I_OL = 8 mA / I_OH = −0.4 mA - sufficient to directly drive multiple 74LS inputs or LED indicators with series resistor.
Pulse Width Range	Externally adjustable via R_EXT and C_EXT; typical t_W = 11 ns at R = 1 kΩ, C = 10 pF (per channel).
Propagation Delay	t_PLH/t_PHL ≤ 45 ns (max) - enables reliable operation in sub-20 MHz digital timing chains.
Supply Voltage	V_CC = 4.75 V to 5.25 V - tight regulation required for stable timing accuracy and noise immunity.

Pinout & Package

SOP (NS) package: 16-pin surface-mount small-outline package with gull-wing leads, 1.27 mm pitch, 8.1 mm × 10.4 mm body size, and 2.00 mm maximum height. Pin 1 marked by notch or beveled corner on top surface.

Pin/Terminal	Circuit Role	Design Meaning
1, 9	A Input (Channel 1 & 2)	Negative-edge trigger input; active-low transition initiates or re-triggers monostable output pulse.
2, 10	B Input (Channel 1 & 2)	Positive-edge trigger input; active-high transition initiates or re-triggers monostable output pulse.
3, 11	CLR (Channel 1 & 2)	Asynchronous reset; low level forces Q = 0 and Q̅ = 1 regardless of timing state.
4, 12	V_CC	+5 V power supply connection; decoupling capacitor recommended near pin.
5, 13	GND	Ground reference for all internal logic and output stages.
6, 14	R_EXT/C_EXT (Channel 1 & 2)	External timing network connection point; sets output pulse width (t_W ≈ 0.32 × R × C).
7, 15	Q Output (Channel 1 & 2)	Active-high monostable output; goes high for duration t_W after valid trigger event.
8, 16	Q̅ Output (Channel 1 & 2)	Complementary active-low output; inverted version of Q output.

Key Features

Feature	Design Value
Retriggerable operation	Enables dynamic pulse extension during active output - critical for debouncing switches or synchronizing variable-rate events.
Dual independent channels	Two fully isolated monostables in one 16-pin SOP package reduce board space and interconnect complexity vs discrete solutions.
Edge-selectable triggering	Separate A (negative-edge) and B (positive-edge) inputs per channel allow flexible interface with diverse signal sources.
LS-TTL compatible I/O	Meets 74LS voltage thresholds and drive strength, ensuring seamless integration into existing TTL-based control logic.
External RC timing	Wide pulse width range (nanoseconds to seconds) set by user-selected R/C values - no internal oscillator or trimming required.

Applications

Industrial Control Timing	Legacy System Pulse Shaping
Use Scenario: Generating fixed-duration enable pulses for stepper motor drivers in PLC-based motion control cabinets. IC Role / Device Role / Timing Role: Dual-channel monostable provides synchronized gate-enable windows for two-phase motor sequencing. Use Value: Retriggerability accommodates jog-mode commands without interrupting ongoing step cycles, improving real-time responsiveness.	Use Scenario: Converting irregular mechanical switch closures into clean, jitter-free digital pulses for microcontroller input capture. IC Role / Device Role / Timing Role: Monostable acts as hardware debouncer and pulse stretcher, eliminating software polling overhead. Use Value: External RC tuning allows precise 20 ms pulse width matching legacy system timing requirements across temperature.
Test Equipment Signal Gating	Digital Logic Debug Interface
Use Scenario: Enabling analog-to-digital conversion windows in automated test fixtures with variable sampling intervals. IC Role / Device Role / Timing Role: One channel generates ADC start pulse; second channel gates sample-and-hold enable based on trigger edge. Use Value: Independent timing networks per channel support asymmetric pulse widths needed for acquisition hold timing margins.	Use Scenario: Inserting controllable delay or pulse-width modulation into FPGA debug trace signals for protocol analysis. IC Role / Device Role / Timing Role: SN74LS123NS serves as programmable pulse generator feeding logic analyzer trigger inputs. Use Value: SOP-16 footprint allows direct replacement of obsolete DIP versions on aging test board revisions without layout change.

Industrial Control Timing

Legacy System Pulse Shaping

Use Scenario: Generating fixed-duration enable pulses for stepper motor drivers in PLC-based motion control cabinets.

IC Role / Device Role / Timing Role: Dual-channel monostable provides synchronized gate-enable windows for two-phase motor sequencing.

Use Value: Retriggerability accommodates jog-mode commands without interrupting ongoing step cycles, improving real-time responsiveness.

Use Scenario: Converting irregular mechanical switch closures into clean, jitter-free digital pulses for microcontroller input capture.

IC Role / Device Role / Timing Role: Monostable acts as hardware debouncer and pulse stretcher, eliminating software polling overhead.

Use Value: External RC tuning allows precise 20 ms pulse width matching legacy system timing requirements across temperature.

Test Equipment Signal Gating

Digital Logic Debug Interface

Use Scenario: Enabling analog-to-digital conversion windows in automated test fixtures with variable sampling intervals.

IC Role / Device Role / Timing Role: One channel generates ADC start pulse; second channel gates sample-and-hold enable based on trigger edge.

Use Value: Independent timing networks per channel support asymmetric pulse widths needed for acquisition hold timing margins.

Use Scenario: Inserting controllable delay or pulse-width modulation into FPGA debug trace signals for protocol analysis.

IC Role / Device Role / Timing Role: SN74LS123NS serves as programmable pulse generator feeding logic analyzer trigger inputs.

Use Value: SOP-16 footprint allows direct replacement of obsolete DIP versions on aging test board revisions without layout change.

Equivalent & Alternatives

The following parts are listed as comparable options for similar retriggerable monostable multivibrator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74LS123N	Same logic function and timing specs, but in through-hole PDIP-16 package (13.97 mm width, 506 mm tube length).	Requires PCB through-hole mounting; not suitable for new SMT designs or space-constrained layouts.	Select SN74LS123N only for repair of legacy through-hole systems where SOP footprint is unavailable.
SN74LS123DR	Identical electrical specs and SOP-16 pinout, but in SOIC-D package (7.62 mm width, 1.75 mm height, 1.27 mm pitch).	SOIC-D has narrower body and different thermal profile; may require stencil redesign for solder paste volume control.	Choose SN74LS123DR when board assembly uses SOIC-compatible tooling and tighter height constraints apply.

Compared with SN74LS123N and SN74LS123DR, the SN74LS123NS offers identical functionality in a wider SOP-NS body optimized for robust solder joint formation and higher thermal mass-making it preferred for industrial environments with thermal cycling stress.

Availability

SN74LS123NS is available at Aetrix Electronics and suitable for industrial control timing, legacy system pulse shaping, test equipment signal gating, and digital logic debug interface applications requiring stable component supply and long-term obsolescence mitigation.

Supply support for SN74LS123NS 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 founded in 1930, specializing in analog, embedded processing, and logic products with broad industrial and automotive qualification.

The SN74LS123NS belongs to TI's legacy 74LS logic family, designed specifically for robust, temperature-stable timing functions in commercial-grade digital systems where retriggerable pulse generation is essential.

FAQ

What is the primary function of the SN74LS123NS?

The SN74LS123NS is a dual retriggerable monostable multivibrator IC that generates precise, externally timed output pulses in response to input triggers. Each of its two independent channels accepts either negative- or positive-edge triggers and supports retriggering during active output-making SN74LS123NS ideal for debounce, pulse stretching, and timing synchronization in legacy TTL systems.

Does the SN74LS123NS support both rising- and falling-edge triggering?

Yes, the SN74LS123NS supports edge-selectable triggering per channel: the A input responds to falling edges (active-low), while the B input responds to rising edges (active-high). This dual-trigger capability allows flexible integration with diverse signal sources without external inverters, and is explicitly defined in the SN74LS123NS datasheet for both channels.

What package type does the SN74LS123NS use, and how does it differ from SN74LS123N?

The SN74LS123NS uses a 16-pin SOP (NS) package-surface-mount, 8.1 mm × 10.4 mm body, 2.00 mm max height-while SN74LS123N uses a through-hole PDIP-16 package. The NS variant enables automated SMT assembly and better thermal performance in compact layouts, whereas the N variant requires manual or wave-solder processes.

Can the SN74LS123NS replace SN74LS123DR in an existing design?

Yes, the SN74LS123NS is pin-compatible with SN74LS123DR in SOP-16 configuration, sharing identical pinout, electrical specs, and timing behavior. However, the NS package has a wider body (10.4 mm vs 7.62 mm) and greater height (2.00 mm vs 1.75 mm), so board layout and stencil aperture must be verified for mechanical fit and solder joint integrity before substitution.

What is the recommended external timing component range for the SN74LS123NS?

The SN74LS123NS supports external RC timing networks with R_EXT from 1 kΩ to 40 kΩ and C_EXT from 10 pF to 10 µF, enabling pulse widths from ~10 ns to several seconds. For stable operation, TI recommends using metal-film resistors and NP0/C0G ceramic capacitors; timing tolerance is ±20% over temperature and voltage per the SN74LS123NS datasheet.

SN74LS123NS Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LS

Package/Case:: 16-SOIC (0.209", 5.30mm Width)

Packaging:: Tube

Product Status:: Obsolete

Logic Type:: Monostable

Independent Circuits:: 2

Schmitt Trigger Input:: No

Propagation Delay:: 34 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-SO

SN74LS123NS FAQ

1.How can I place an order for SN74LS123NS through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LS123NS 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 SN74LS123NS reliable?

The price and inventory of SN74LS123NS are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS123NS is usually 5 days.

3.What payment methods are accepted for SN74LS123NS?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS123NS transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LS123NS?

SN74LS123NS orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LS123NS 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 SN74LS123NS?

For technical support, including SN74LS123NS datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS123NS requirements.

6.How does Aetrix verify that SN74LS123NS is sourced from the original manufacturer or authorized distributors?

All SN74LS123NS 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 SN74LS123NS meets industry standards.

7.What is the process for return or replacement of SN74LS123NS?

All SN74LS123NS units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS123NS, 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 SN74LS123NS part is unused and in its original packaging.

Return procedure for SN74LS123NS:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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