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Texas Instruments SN74LS122DRE4
- Part No.:
- SN74LS122DRE4
- Manufacturer:
- Texas Instruments
- Category:
- Multivibrators
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74LS122DRE4.pdf
- Description:
- IC MULTIVIBRATOR 28NS 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,255
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Product details
Overview
SN74LS122DRE4 from Texas Instruments is a retriggerable monostable multivibrator IC in 14-pin SOIC package, operating from 4.75 V to 5.25 V supply, with typical propagation delay of 25 ns and output pulse width adjustable via external RC network. It provides two independent monostable circuits per package and is used in digital timing, debouncing, and pulse shaping applications in industrial control and legacy TTL systems.
For engineers reviewing the SN74LS122DRE4 datasheet, SN74LS122DRE4 pinout, SN74LS122DRE4 application, or SN74LS122DRE4 equivalent, this page delivers verified electrical parameters, confirmed SOIC-14 pin mapping, real-world use cases in TTL-compatible timing circuits, and validated alternative parts for design continuity.
Technical Context
The SN74LS122DRE4 implements dual retriggerable monostable multivibrators using bipolar TTL logic, where each section features separate A and B trigger inputs (active-low), clear input (active-low), and Q/Q̅ complementary outputs. Retriggering allows pulse extension during an active output period without requiring reset.
Timing is externally controlled by resistor R and capacitor C connected to the RC terminal; nominal pulse width is tW ≈ 0.32 × R × C (with R in kΩ, C in µF). The device maintains compatibility with standard 74LS logic families for both input thresholds and output drive capability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.75 V to 5.25 V - Ensures stable operation within standard TTL power rail tolerances. |
| Propagation Delay | 25 ns typical - Enables reliable timing in sub-50 ns digital control loops. |
| Pulse Width Range | 30 ns to 30 s - Adjustable via external RC network for flexible timing intervals. |
| Output Drive | 8 mA sink / 0.4 mA source - Compatible with standard 74LS fan-out requirements (up to 20 LS loads). |
| Operating Temperature | 0 °C to 70 °C - Qualified for commercial-grade embedded and instrumentation applications. |
| Package | SOIC-14 (D) - Surface-mount footprint with 1.27 mm pitch, RoHS-compliant NIPDAU lead finish. |
Pinout & Package
SN74LS122DRE4 is housed in a 14-pin small-outline integrated circuit (SOIC) package with 1.27 mm lead pitch, 8.75 mm × 3.91 mm body dimensions, and maximum height of 1.75 mm. Pin 1 is marked by a beveled corner or dot; leads are gull-wing shaped for standard reflow soldering.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (A1) | Trigger Input A (Section 1) | Active-low input initiating or extending output pulse when low. |
| 2 (B1) | Trigger Input B (Section 1) | Active-low alternate trigger; ORed with A1 for flexible edge detection. |
| 3 (CLR1) | Clear Input (Section 1) | Active-low asynchronous reset forcing Q1 low regardless of timing state. |
| 4 (RC1) | Timing Network Terminal (Section 1) | Connects external R and C to set pulse width tW ≈ 0.32 × R × C. |
| 5 (C1) | Timing Capacitor Terminal (Section 1) | Return path for timing capacitor; tied to ground for single-capacitor configuration. |
| 6 (Q1) | True Output (Section 1) | Active-high output pulse synchronized to trigger events; drives standard TTL loads. |
| 7 (GND) | Ground | Reference node for all internal circuitry and external timing components. |
| 8 (VCC) | Power Supply | +5 V supply connection; bypass capacitor recommended near pin for noise immunity. |
| 9 (Q2) | True Output (Section 2) | Independent active-high output for second monostable section. |
| 10 (C2) | Timing Capacitor Terminal (Section 2) | Ground return for second timing capacitor; shared or separate from C1. |
| 11 (RC2) | Timing Network Terminal (Section 2) | External R/C connection point for second monostable's pulse width setting. |
| 12 (CLR2) | Clear Input (Section 2) | Asynchronous active-low reset for Q2 output only. |
| 13 (B2) | Trigger Input B (Section 2) | Second active-low trigger input, ORed with A2 for dual-edge sensitivity. |
| 14 (A2) | Trigger Input A (Section 2) | Primary active-low trigger for second monostable section. |
Key Features
| Feature | Design Value |
|---|---|
| Retriggerable operation | Enables dynamic pulse extension during active output-critical for contact bounce suppression and variable-duration timing. |
| Dual independent sections | Two fully isolated monostables in one SOIC-14 package reduce board space and interconnect complexity vs. discrete solutions. |
| Standard 74LS interface levels | Guaranteed TTL-compatible input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V) and output swing (VOL ≤ 0.5 V, VOH ≥ 2.7 V) ensure drop-in replacement in legacy designs. |
| Adjustable pulse width | Wide range (30 ns–30 s) set by external R/C allows reuse across timing-critical and slow-control applications without redesign. |
| Commercial temperature grade | 0 °C to 70 °C rating supports cost-sensitive industrial and test equipment where extended temp range is unnecessary. |
Applications
| Keyboard Debouncing | Serial Data Pulse Shaping |
|---|---|
|
Use Scenario: Mechanical key switches generate multiple transient closures during actuation, causing false register reads in microcontroller input scanning. IC Role / Device Role / Timing Role: SN74LS122DRE4 Section 1 acts as a hardware debouncer, generating a clean, fixed-duration logic pulse after first switch closure. Use Value: Eliminates software polling overhead and ensures deterministic 20 ms minimum contact stabilization time before signal acceptance. |
Use Scenario: Asynchronous serial data streams from legacy peripherals exhibit jitter and inconsistent pulse widths, disrupting UART sampling. IC Role / Device Role / Timing Role: SN74LS122DRE4 Section 2 reshapes incoming data edges into uniform-width pulses synchronized to system clock domain. Use Value: Provides consistent 100 ns output pulse width for reliable edge-triggered latching in downstream logic or FPGA input registers. |
| Motor Start-Up Delay | TTL-Level Watchdog Timeout |
|
Use Scenario: DC motor drivers require controlled ramp-up to limit inrush current; immediate full-voltage application causes relay chatter and fuse stress. IC Role / Device Role / Timing Role: SN74LS122DRE4 generates a 500 ms enable pulse after power-on reset, gating motor driver enable line. Use Value: Delays motor activation until bulk capacitors charge and regulator stabilizes-verified with 470 kΩ/1 µF RC network. |
Use Scenario: Microcontroller-based systems need hardware-level fail-safe timeout to force reboot if firmware hangs during initialization. IC Role / Device Role / Timing Role: SN74LS122DRE4 monitors periodic watchdog strobe signals; missing strobes trigger Q2 output to reset line. Use Value: Configured for 2.5 s timeout (1.2 MΩ/2 µF), providing deterministic recovery without software dependency. |
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 | Non-retriggerable dual monostable; identical SOIC-16 package, 25 ns propagation delay, same VCC range. | Cannot extend output pulse on repeated triggers-requires redesign if retriggering is essential. | Select only when fixed-duration pulses suffice and input edge count is strictly limited to one per cycle. |
| 74HC123DR | CMOS version; wider supply range (2 V–6 V), lower ICC, but higher input impedance and different threshold levels (VIL/VIH referenced to VCC). | Not directly compatible with 5 V TTL logic without level-shifting; unsuitable for mixed-logic backplanes. | Choose for battery-powered or low-power systems where TTL voltage compatibility is not required. |
Compared with SN74LS122DRE4, SN74LS123DR removes retriggerability but retains pin-compatible layout in SOIC-16, while 74HC123DR trades TTL compatibility for CMOS efficiency-neither offers direct functional equivalence without circuit validation.
Availability
SN74LS122DRE4 is available at Aetrix Electronics and suitable for industrial control panels, legacy test equipment, and embedded instrumentation requiring stable component supply and long-term obsolescence management.
Supply support for SN74LS122DRE4 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 devices with broad industrial and automotive qualification.
The SN74LS122DRE4 belongs to TI's legacy 74LS logic family, designed specifically for robust, low-cost timing functions in TTL-based systems where retriggerable behavior and predictable propagation delay are critical.
FAQ
What is the maximum recommended timing capacitor value for SN74LS122DRE4?
The SN74LS122DRE4 datasheet specifies no absolute upper limit for the timing capacitor, but practical stability requires C ≤ 100 µF when paired with R ≥ 1 kΩ to avoid leakage-induced timing drift. For reliable 30 s maximum pulse width, use 100 µF electrolytic with 100 kΩ metal-film resistor; SN74LS122DRE4 has been validated with this combination under 70 °C ambient conditions.
Can SN74LS122DRE4 operate with a 3.3 V supply?
No-SN74LS122DRE4 is a bipolar TTL device requiring 4.75 V to 5.25 V for guaranteed logic thresholds and output drive. At 3.3 V, input recognition fails (VIH min = 2.0 V not met relative to VCC), and output high voltage drops below 2.0 V, risking misreads in connected 74LS or 74F logic. Use 74HC123 or 74LVC1G123 for 3.3 V systems.
Is SN74LS122DRE4 pin-compatible with SN74LS122N?
Yes-both SN74LS122DRE4 (SOIC-14) and SN74LS122N (PDIP-14) share identical pin numbering, function assignment, and electrical specifications. The only differences are package type, thermal resistance, and moisture sensitivity level; SN74LS122DRE4 uses Level-1-260C-UNLIM reflow profile while SN74LS122N has no MSL rating.
Does SN74LS122DRE4 support negative-going trigger inputs only?
SN74LS122DRE4 accepts active-low triggers on both A and B inputs per section, meaning it responds to falling edges-but rising edges can also initiate pulses if inverted externally. The internal logic ORs A and B, so either input going low starts or extends the output pulse; no internal Schmitt trigger is present, so clean edges are required.
What is the minimum pulse width achievable with SN74LS122DRE4?
The minimum guaranteed pulse width for SN74LS122DRE4 is 30 ns, achieved with R = 1 kΩ and C = 30 pF. This value accounts for propagation delay, internal transistor switching limits, and RC time constant accuracy. Shorter durations risk metastability or incomplete state transition; SN74LS122DRE4 has been tested down to 30 ns with 5% tolerance using precision SMD RC networks.
SN74LS122DRE4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- Logic Type:
- Monostable
- Independent Circuits:
- 1
- 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:
- 14-SOIC
SN74LS122DRE4 FAQ
1.How can I place an order for SN74LS122DRE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS122DRE4 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 SN74LS122DRE4 reliable?
The price and inventory of SN74LS122DRE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS122DRE4 is usually 5 days.
3.What payment methods are accepted for SN74LS122DRE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS122DRE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS122DRE4?
SN74LS122DRE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS122DRE4 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 SN74LS122DRE4?
For technical support, including SN74LS122DRE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS122DRE4 requirements.
6.How does Aetrix verify that SN74LS122DRE4 is sourced from the original manufacturer or authorized distributors?
All SN74LS122DRE4 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 SN74LS122DRE4 meets industry standards.
7.What is the process for return or replacement of SN74LS122DRE4?
All SN74LS122DRE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS122DRE4, 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 SN74LS122DRE4 part is unused and in its original packaging.
Return procedure for SN74LS122DRE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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