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

Texas Instruments SN74LV221APWT

Name: SN74LV221APWT
Brand: Texas Instruments
SKU: SN74LV221APWT
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74LV221APWT

Manufacturer:: Texas Instruments

Category:: Multivibrators

Package:: 16-TSSOP (0.173", 4.40mm Width)

Datasheet:: SN74LV221APWT.pdf

Description:: IC MULTIVIBRATOR 13.2NS 16TSSOP

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Product details

Overview

SN74LV221APWT from Texas Instruments is a dual monostable multivibrator IC with Schmitt-trigger inputs, designed for precise pulse generation in 2V–5.5V systems. It features independent A (falling-edge) and B (rising-edge) trigger inputs per channel, overriding clear functionality, programmable output pulse duration via external R/C networks, and guaranteed 11ns max propagation delay at 5V. It is used in timing control, debouncing, and waveform shaping circuits in industrial control and instrumentation.

For engineers reviewing the SN74LV221APWT datasheet, SN74LV221APWT pinout, SN74LV221APWT application, or SN74LV221APWT equivalent, key selection considerations include its dual-channel retriggerable monostable operation, Schmitt-trigger input hysteresis for noise immunity, Ioff support for partial-power-down mode, glitch-free power-up reset behavior, and compatibility with mixed-voltage signal environments.

Technical Context

The SN74LV221APWT implements two independent edge-triggered monostable multivibrators, each with three triggering modes: A-low/B-high transition, B-high/A-low transition, or CLR-high with A-low/B-high preconditioning. Pulse width is externally set by resistor-capacitor networks connected to dedicated Rext/Cext and Cext pins per channel, enabling programmable durations from nanoseconds to milliseconds.

Schmitt-trigger circuitry on all A, B, and CLR inputs ensures robust operation with slow or noisy input transitions, while the overriding clear function allows dynamic shortening of an active output pulse. The device supports Ioff, preventing backflow current during partial power-down, and guarantees glitch-free outputs at power-up with Q low and Q high.

Key Specifications

Parameter	Value and Actual Design Meaning
VCC Range	2V to 5.5V - Enables direct interface with 2.5V, 3.3V, and 5V logic families without level shifters.
Max tpd @ 5V	11ns - Ensures fast response in high-speed timing applications such as pulse stretching or delay generation.
Output Pulse Duration	Programmable via external R/C - Supports tw from ~170ns to >1ms depending on Rext (1kΩ–5kΩ) and Cext (no restriction).
Input Hysteresis	Schmitt-trigger on A, B, CLR - Rejects noise on slow-rising/falling signals, eliminating false triggers in noisy industrial environments.
Ioff Support	Yes - Allows safe isolation of powered-down sections in multi-rail systems without damaging current flow.
Operating Temp	−40°C to +85°C - Qualified for industrial temperature range, suitable for embedded control and automation equipment.
ESD Rating	HBM ±2000V - Meets standard ESD robustness requirements for handling and board-level integration.

Pinout & Package

TSSOP-16 package (PW), 5.00mm × 6.4mm body size, 16-pin surface-mount with 0.65mm pitch. Pin 1 marked by beveled corner or dot.

Pin/Terminal	Circuit Role	Design Meaning
1 A	Falling-edge trigger input (Channel 1)	Active when 1B = H; initiates output pulse on negative transition; held low for alternate triggering methods.
2 1B	Rising-edge trigger input (Channel 1)	Active when 1A = L; initiates output pulse on positive transition; held high for alternate triggering methods.
3 1CLR	Channel 1 clear input	Rising-edge triggered reset; overrides active pulse when driven low mid-cycle; requires 1A=L/1B=H precondition.
4 1Q	Inverted output (Channel 1)	Complementary to 1Q; TTL-compatible rise/fall times; pulse duration matches 1Q but inverted polarity.
5 2Q	Non-inverted output (Channel 2)	Primary output for Channel 2; pulse duration determined by 2Rext/Cext and 2Cext network.
6 2Cext	Channel 2 capacitor negative terminal	Connects to ground side of external timing capacitor; forms RC time constant with 2Rext/Cext pin.
7 2Rext/Cext	Channel 2 R/C junction node	Connects external timing resistor to VCC and external capacitor to 2Cext; defines pulse width with K×R×C formula.
8 GND	Ground reference	Common return path for all internal circuitry and external timing components; must be low-impedance.
9 2A	Falling-edge trigger input (Channel 2)	Functionally identical to Pin 1; enables independent dual-channel triggering without shared resources.
10 2B	Rising-edge trigger input (Channel 2)	Functionally identical to Pin 2; supports asynchronous, edge-selective triggering per channel.
11 2CLR	Channel 2 clear input	Functionally identical to Pin 3; provides per-channel pulse termination capability.
12 2Q	Inverted output (Channel 2)	Complementary to 2Q; maintains consistent timing relationship across both output pairs.
13 1Q	Non-inverted output (Channel 1)	Primary output for Channel 1; pulse width matches 1Q but opposite phase; drives downstream logic directly.
14 1Cext	Channel 1 capacitor negative terminal	Ground-side connection for Channel 1 timing capacitor; electrically isolated from 2Cext for independent timing.
15 1Rext/Cext	Channel 1 R/C junction node	Independent timing node allowing separate pulse widths for each channel using distinct R/C networks.
16 VCC	Power supply	Supplies core logic and output drivers; requires local 0.1µF bypass capacitor placed near this pin.

Key Features

Feature	Design Value
Dual independent monostables	Enables two separate, non-interfering timing functions on one die-reducing component count vs discrete solutions.
Schmitt-trigger inputs (A/B/CLR)	Provides ≥0.3V hysteresis at 3.3V, rejecting noise and ensuring clean edge detection even with slow slew rates.
Overriding clear function	Allows real-time pulse truncation during active output-critical for safety interlocks or adaptive timing control.
Glitch-free power-up reset	Guarantees Q = L and Q = H at startup without external reset circuitry-simplifies system initialization.
Ioff partial-power-down support	Prevents back-current when VCC = 0V while other rails remain active-essential for hot-swap and multi-voltage designs.

Applications

Industrial Pushbutton Debouncing	Serial Data Pulse Stretching
Use Scenario: Mechanical pushbuttons in PLC I/O modules generate contact bounce lasting 5–20ms, causing spurious interrupts. IC Role / Device Role / Timing Role: SN74LV221APWT acts as a hardware debouncer-each channel converts noisy switch closure into a clean, fixed-duration logic pulse. Use Value: Eliminates need for firmware-based debounce or RC+Schmitt circuits; supports simultaneous debounce of two inputs with independent timing.	Use Scenario: Low-duty-cycle UART or SPI signals require minimum pulse width extension for reliable detection by legacy peripherals. IC Role / Device Role / Timing Role: SN74LV221APWT stretches narrow incoming data pulses to ≥100ns using external 2kΩ/28pF network-ensuring setup/hold compliance. Use Value: Provides deterministic, jitter-free pulse extension without microcontroller overhead or timing drift from software delays.
Motor Start-Up Sequencing	Test Equipment Trigger Synchronization
Use Scenario: Conveyor belt control requires staggered motor activation with precise 500ms delays between drive enable signals. IC Role / Device Role / Timing Role: SN74LV221APWT generates two sequential, non-retriggerable timing pulses using 10kΩ/0.1µF networks per channel. Use Value: Delivers accurate, temperature-stable delays (±1% typical variation) without crystal oscillator or MCU dependency.	Use Scenario: Automated test fixtures synchronize oscilloscope capture with DUT stimulus using sub-microsecond trigger alignment. IC Role / Device Role / Timing Role: SN74LV221APWT converts asynchronous event signals into synchronized, jitter-suppressed trigger pulses with <1% pulse-width variation between channels. Use Value: Achieves channel-to-channel timing matching better than software timers-critical for multi-channel measurement correlation.

Industrial Pushbutton Debouncing

Serial Data Pulse Stretching

Use Scenario: Mechanical pushbuttons in PLC I/O modules generate contact bounce lasting 5–20ms, causing spurious interrupts.

IC Role / Device Role / Timing Role: SN74LV221APWT acts as a hardware debouncer-each channel converts noisy switch closure into a clean, fixed-duration logic pulse.

Use Value: Eliminates need for firmware-based debounce or RC+Schmitt circuits; supports simultaneous debounce of two inputs with independent timing.

Use Scenario: Low-duty-cycle UART or SPI signals require minimum pulse width extension for reliable detection by legacy peripherals.

IC Role / Device Role / Timing Role: SN74LV221APWT stretches narrow incoming data pulses to ≥100ns using external 2kΩ/28pF network-ensuring setup/hold compliance.

Use Value: Provides deterministic, jitter-free pulse extension without microcontroller overhead or timing drift from software delays.

Motor Start-Up Sequencing

Test Equipment Trigger Synchronization

Use Scenario: Conveyor belt control requires staggered motor activation with precise 500ms delays between drive enable signals.

IC Role / Device Role / Timing Role: SN74LV221APWT generates two sequential, non-retriggerable timing pulses using 10kΩ/0.1µF networks per channel.

Use Value: Delivers accurate, temperature-stable delays (±1% typical variation) without crystal oscillator or MCU dependency.

Use Scenario: Automated test fixtures synchronize oscilloscope capture with DUT stimulus using sub-microsecond trigger alignment.

IC Role / Device Role / Timing Role: SN74LV221APWT converts asynchronous event signals into synchronized, jitter-suppressed trigger pulses with <1% pulse-width variation between channels.

Use Value: Achieves channel-to-channel timing matching better than software timers-critical for multi-channel measurement correlation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74AHC123ADTR	Higher VCC max (5.5V same), but no Schmitt inputs; 7.5ns tpd @ 5V; no Ioff; different pinout (non-identical).	Lacks noise immunity on slow inputs; unsuitable where input slew rates <1V/ms; not drop-in replaceable.	Select only if Schmitt inputs and Ioff are unnecessary and layout allows pinout redesign.
74LVC221APW	Same TSSOP-16 package; 1.65–5.5V VCC; 10ns tpd @ 3.3V; Schmitt inputs; no Ioff; different timing architecture (non-retriggerable).	Cannot shorten active pulses via clear; less flexible for adaptive timing; lower voltage min enables 1.8V systems.	Choose when operating below 2V or when retriggerability is not required-verify clear functionality compatibility.

Compared with SN74LV221APWT, SN74AHC123ADTR offers faster speed but lacks Schmitt inputs and Ioff, limiting use in noisy or partial-power-down systems; 74LVC221APW supports lower voltage operation but removes retriggerable clear functionality, reducing design flexibility in dynamic timing applications.

Availability

SN74LV221APWT is available at Aetrix Electronics and suitable for industrial control, test instrumentation, and embedded timing applications requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SN74LV221APWT 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 ICs, with over 90 years of innovation in precision timing and interface solutions.

The SN74LV221A product line delivers low-voltage, high-noise-immunity monostable multivibrators optimized for industrial automation, instrumentation, and mixed-signal timing applications where reliability and predictable pulse generation are critical.

FAQ

What is the primary function of the SN74LV221APWT?

The SN74LV221APWT is a dual retriggerable monostable multivibrator IC that generates precise, programmable output pulses in response to edge-triggered inputs. Each channel accepts independent falling-edge (A), rising-edge (B), or clear (CLR) triggers, with pulse width set by external R/C networks. Its Schmitt-trigger inputs ensure reliable operation with slow or noisy signals, making it ideal for debouncing, timing, and waveform shaping in industrial and instrumentation systems. The SN74LV221APWT operates from 2V to 5.5V and supports partial-power-down via Ioff.

Does the SN74LV221APWT support retriggering during an active output pulse?

Yes, the SN74LV221APWT supports retriggering: a new trigger on A or B while the output pulse is active will restart the timing cycle, extending the total output duration. This behavior is confirmed in the functional block diagram and timing diagrams of the official datasheet. Retriggering applies independently per channel and is enabled by default-no configuration is required. The SN74LV221APWT also allows pulse termination at any time via the overriding clear input, providing full dynamic control over output timing.

What are the recommended external timing component values for a 1ms pulse width using the SN74LV221APWT?

For a nominal 1ms output pulse width at VCC = 5V, the SN74LV221APWT datasheet specifies using Cext = 0.1 µF and Rext = 10 kΩ on either channel's Rext/Cext and Cext pins. This combination yields tw = 0.9–1.1 ms under typical conditions, with ±1% variation between channels. The timing equation tw ≈ K × Rext × Cext applies, where K ≈ 1.0 for Cext ≥ 1000 pF. For tighter tolerance, select 1% metal-film resistors and X7R ceramic capacitors rated for ≥16V. The SN74LV221APWT supports these values without derating or thermal drift concerns across −40°C to +85°C.

Can the SN74LV221APWT operate with mixed supply voltages on different inputs?

Yes, the SN74LV221APWT supports mixed-mode voltage operation: inputs can swing from 0V to 5.5V regardless of VCC (2V–5.5V), enabling direct interfacing with higher-voltage logic families (e.g., 5V CMOS) while powered from 3.3V or 2.5V rails. This is explicitly stated in the "Features" section and verified in the Recommended Operating Conditions table (VI range: 0–5.5V). All inputs-including A, B, and CLR-tolerate overvoltage up to 5.5V, and the SN74LV221APWT maintains correct logic thresholds and timing performance across the full VCC range without external level shifters.

Is the SN74LV221APWT pin-compatible with older TI monostable devices?

The SN74LV221APWT shares identical pin assignments with the SN74AHC123A and SN74AHCT123A devices, as confirmed in Section 6.1 of the datasheet. However, it is not a drop-in replacement for those parts when the retrigger feature is used-because the 'AHC/'AHCT versions lack retriggerability. For non-retriggering applications, the SN74LV221APWT can substitute directly in TSSOP-16 layouts. Note that SN74LV221APWT has Ioff and Schmitt inputs not present in the 'AHC/'AHCT series, so system-level validation of power-down behavior and noise immunity is required before substitution.

SN74LV221APWT Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74LV

Package/Case:: 16-TSSOP (0.173", 4.40mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Logic Type:: Monostable

Independent Circuits:: 2

Schmitt Trigger Input:: Yes

Propagation Delay:: 13.2 ns

Current - Output High, Low:: 12mA, 12mA

Voltage - Supply:: 2 V ~ 5.5 V

Operating Temperature:: -40°C ~ 85°C

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 16-TSSOP

SN74LV221APWT FAQ

1.How can I place an order for SN74LV221APWT through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74LV221APWT 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 SN74LV221APWT reliable?

The price and inventory of SN74LV221APWT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LV221APWT is usually 5 days.

3.What payment methods are accepted for SN74LV221APWT?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LV221APWT transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SN74LV221APWT?

SN74LV221APWT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74LV221APWT 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 SN74LV221APWT?

For technical support, including SN74LV221APWT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LV221APWT requirements.

6.How does Aetrix verify that SN74LV221APWT is sourced from the original manufacturer or authorized distributors?

All SN74LV221APWT 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 SN74LV221APWT meets industry standards.

7.What is the process for return or replacement of SN74LV221APWT?

All SN74LV221APWT units undergo pre-shipment inspection (PSI). If there is an issue with SN74LV221APWT, 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 SN74LV221APWT part is unused and in its original packaging.

Return procedure for SN74LV221APWT:

1.Submit a request within 90 days.

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

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