Texas Instruments CD74HC123PWRE4

Overview

CD74HC123PWRE4 from Texas Instruments is a dual retriggerable monostable multivibrator with independent resets, Schmitt-trigger inputs on both A and B trigger lines, buffered Q and Q̅ outputs, and external RC timing control (t_W = 0.45·R_XC_X at V_CC = 5V). It operates from 2V to 6V, supports -55°C to +125°C industrial/military temperature range, and delivers precise pulse widths from microseconds to seconds in timing-critical digital systems such as debounce circuits and event synchronization.

For engineers reviewing the CD74HC123PWRE4 datasheet, CD74HC123PWRE4 pinout, CD74HC123PWRE4 application, or CD74HC123PWRE4 equivalent, this page provides verified functional identity, validated TSSOP-16 pin mapping, confirmed retriggerable monostable behavior, exact timing equation and tolerance data, and two industry-validated alternative parts for design flexibility.

Technical Context

The CD74HC123PWRE4 implements two independent monostable multivibrators, each with separate A (trailing-edge), B (leading-edge), and R (active-low reset) inputs. Triggering is edge-sensitive and retriggerable - a new input edge during an active output pulse extends t_W, while a LOW on R terminates it immediately. Each mono features Schmitt-trigger inputs for noise immunity and hysteresis of ~1.2V at V_CC = 5V.

Timing is set externally via R_X (≥5 kΩ min) and C_X (0 pF min); pulse width accuracy depends on component tolerances and V_CC-dependent K-factor (0.45 typ. at 5V). Propagation delays (e.g., 64 ns max A→Q at V_CC = 4.5V, -55°C to +125°C) and pulse-width match (±2% between monos) are specified across full temperature range.

Key Specifications

Pinout & Package

CD74HC123PWRE4 is housed in a 16-pin TSSOP package (PW), 4.4 mm × 5.0 mm footprint, 1.2 mm max height, with 0.65 mm pitch and exposed pad not electrically connected. Pin 1 marked by index area; pinout follows JEDEC MO-153 standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC123M96, CD74HC123PWRE4 offers 30% smaller PCB area and better high-temp performance but requires tighter thermal management; versus SN74LV123AIPWR, it trades 10× higher noise immunity and military-grade temperature range for modest speed reduction - making CD74HC123PWRE4 optimal for ruggedized embedded timing.

Availability

CD74HC123PWRE4 is available at Aetrix Electronics and suitable for industrial control panels, aerospace avionics interfaces, and automotive body electronics requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC123PWRE4 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 solutions, with over 90 years of innovation in high-reliability components.

The CD74HC123PWRE4 belongs to TI's legacy HC logic family, designed specifically for robust, low-power, wide-temperature digital timing applications where precision, noise immunity, and field reliability are critical.

FAQ

What is the minimum external resistor value supported by CD74HC123PWRE4?

The CD74HC123PWRE4 specifies a typical minimum external timing resistor R_X of 5 kΩ. Using values below this may cause timing inaccuracies or unstable output due to internal leakage and comparator threshold limitations. For designs requiring shorter pulses, reduce C_X instead - down to 0 pF - while maintaining R_X ≥ 5 kΩ to ensure CD74HC123PWRE4 reliability across -55°C to +125°C.

Can CD74HC123PWRE4 be used with a 3.3V supply?

Yes, CD74HC123PWRE4 is fully specified for 2V to 6V operation, including 3.3V. At V_CC = 3.3V, input thresholds scale proportionally (VIH ≈ 2.3V, VIL ≈ 1.0V), and output drive remains compliant with LVTTL and 3.3V CMOS logic families. The 0.45·R_XC_X timing equation holds, though the K-factor decreases slightly - consult TI's "K Factor vs. V_CC" curve in the CD74HC123PWRE4 datasheet Figure 5 for precise calibration.

Does CD74HC123PWRE4 require pull-up or pull-down resistors on unused inputs?

Yes. Per the CD74HC123PWRE4 datasheet, all unused inputs - including A, B, and R on either mono - must be terminated to a defined logic level (V_CC or GND) to prevent floating nodes, unintended triggering, or excessive ICC current. Leaving them open risks erratic behavior, especially at temperature extremes. Use 10 kΩ pull-up for R (to keep mono disabled) or pull-down for A/B (to disable triggering), depending on desired default state.

How does the reset function interact with retriggering in CD74HC123PWRE4?

In CD74HC123PWRE4, the active-low reset (R) input has absolute priority: asserting R LOW terminates the output pulse immediately, regardless of whether the mono is idle, triggered, or actively retriggered. This override behavior is asynchronous and does not depend on clock edges or timing conditions. Once R returns HIGH, the mono resumes normal operation - if a trigger occurred during reset, it will initiate a new pulse; otherwise, it waits for next valid edge.

Is CD74HC123PWRE4 RoHS-compliant and lead-free?

Yes, CD74HC123PWRE4 is RoHS-compliant and lead-free. Its package uses NiPdAu (NIPDAU) lead finish with Sn (tin) over NiPdAu plating, meeting JEDEC J-STD-609 Category 1 requirements. The device carries "G4" suffix in some variants indicating green packaging, and TI's official packaging addendum confirms RoHS status for CD74HC123PWRE4 with MSL Level-1 rating and peak reflow tolerance up to 260°C.