Texas Instruments SN74LV221AD

Overview

SN74LV221AD from Texas Instruments is a dual monostable multivibrator IC with Schmitt-trigger inputs, designed for 2V–5.5V operation, 11ns max propagation delay at 5V, and programmable output pulse duration via external R/C networks. It serves as a precision timing generator in digital control systems requiring edge-triggered one-shot pulses with glitch-free power-up reset.

For engineers reviewing the SN74LV221AD datasheet, SN74LV221AD pinout, SN74LV221AD application, or SN74LV221AD equivalent, this page delivers verified functional identity, SOIC-16 package mapping, confirmed Schmitt-trigger input behavior, overriding clear functionality, and real-world timing design constraints for reliable implementation in industrial logic interfaces and pulse-shaping circuits.

Technical Context

The SN74LV221AD implements two independent edge-triggered monostable multivibrators per channel, each supporting three trigger modes: negative-edge on A (with B high), positive-edge on B (with A low), or simultaneous A-low/B-high with rising CLR. Each channel features separate external timing terminals (Rext/Cext and Cext) enabling independent pulse-width configuration.

Schmitt-trigger inputs on A, B, and CLR ensure noise-immune triggering across slow input transitions; Ioff circuitry enables partial-power-down mode; and outputs are TTL-compatible with guaranteed VOH/VOL over full VCC range. Glitch-free power-up reset forces Q low and Q high without external initialization.

Key Specifications

Pinout & Package

SN74LV221AD is packaged in a 16-pin SOIC (D) package measuring 9.9mm × 6mm (body: 9.9mm × 3.90mm), with standard 1.27mm pitch and surface-mount compatibility.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74AHC123ADR and SN74LVC1G123DBVR, the SN74LV221AD uniquely combines dual-channel operation, Schmitt-trigger inputs, overriding clear, and Ioff in a single SOIC-16 package - making it the only option for robust, industrial-grade pulse generation with hardware-level fault response.

Availability

SN74LV221AD is available at Aetrix Electronics and suitable for industrial control sequencing, switch debouncing, digital signal edge detection, and asynchronous event synchronization requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SN74LV221AD 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 and embedded processing technologies, with decades of expertise in logic IC design and industrial-grade reliability validation.

The SN74LV221AD belongs to TI's LV family of low-voltage, high-speed logic devices engineered for robust operation across 2V–5.5V supply rails in industrial automation, test equipment, and automotive body electronics.

FAQ

What is the minimum external timing capacitance supported by the SN74LV221AD?

The SN74LV221AD imposes no lower limit on external timing capacitance (Cext); the device functions correctly with values as low as 28pF. However, for accurate pulse-width prediction using the tw = K × RT × CT formula, Cext ≥ 1000pF yields K = 1.0. At smaller values, K must be interpolated from Figure 7-5 in the datasheet. The SN74LV221AD maintains stable triggering and output waveform integrity down to 28pF under 5V operation with 2kΩ Rext.

Does the SN74LV221AD support retriggering during an active output pulse?

No, the SN74LV221AD does not support retriggering during an active output pulse. Once triggered, the output pulse duration is determined solely by the external R/C network and cannot be extended by subsequent A or B input transitions. This non-retriggerable behavior is inherent to the 'LV221A architecture and differs from retriggerable multivibrators like the 'AHC123A. The SN74LV221AD can only terminate an active pulse early via the overriding clear (CLR) input.

Can the SN74LV221AD operate reliably at 2.3V supply voltage?

Yes, the SN74LV221AD is fully specified for operation at 2.3V. Per Section 4.3 of the datasheet, VCC = 2.3V falls within the recommended operating range (2V–5.5V), and electrical characteristics including VOH (min 2.0V), VOL (max 0.4V), and tpd (max 31.4ns at CL = 15pF) are guaranteed at this voltage. The SN74LV221AD maintains Schmitt-trigger hysteresis and Ioff functionality across the entire 2V–5.5V range.

What is the maximum allowable external timing resistance for the SN74LV221AD at 5V operation?

At VCC = 5V, the SN74LV221AD supports external timing resistances up to 100kΩ, as validated by timing characterization data showing stable pulse generation with Rext = 10kΩ and Cext = 0.1µF (yielding ~1ms pulse). While the datasheet specifies a minimum Rext of 1kΩ, no upper limit is defined - however, resistances above 100kΩ increase sensitivity to leakage currents and noise, potentially degrading pulse-width accuracy. The SN74LV221AD remains functional but less precise beyond this value.

Is the SN74LV221AD pin-compatible with the SN74AHC123A?

Yes, the SN74LV221AD has identical pin assignments to the SN74AHC123A and SN74AHCT123A, as explicitly stated in Section 6.1 of the datasheet. This allows direct PCB-level substitution in existing designs - provided the application does not rely on the retriggerable feature of the 'AHC123A, since the SN74LV221AD is non-retriggerable. All 16 pins retain identical electrical roles and physical placement in SOIC packages.