Texas Instruments CD74HC4538ME4

Overview

CD74HC4538ME4 from Texas Instruments is a dual retriggerable/resettable monostable multivibrator in 16-pin SOIC package, operating from 2V to 6V with ±25mA output drive, Schmitt-trigger inputs on A/B, and independent trigger/reset propagation delays unaffected by external timing components RX/CX. It delivers precise pulse widths (e.g., 0.63–0.81 ms with RX=10kΩ, CX=0.1µF) for timing-critical industrial control and instrumentation circuits.

For engineers reviewing the CD74HC4538ME4 datasheet, CD74HC4538ME4 pinout, CD74HC4538ME4 application, or CD74HC4538ME4 equivalent, key selection factors include its wide temperature range (–55°C to +125°C), retriggerable edge-selective triggering (A = leading, B = trailing), buffered Q/Q outputs, and compatibility with both LSTTL and CMOS logic families via HC-level noise immunity (NIL/NIH = 30% at VCC = 5V).

Technical Context

The CD74HC4538ME4 implements two independent monostable sections, each with separate A (leading-edge), B (trailing-edge), R (reset), and RX/CX timing network terminals. Its internal architecture uses Schmitt-trigger input stages and precision RC-controlled one-shot timing, where output pulse width τ ≈ 0.7 × RX × CX, with RX ≥ 5kΩ and CX ≥ 0pF.

Propagation delays (tPLH/tPHL) are independent of RX and CX values-e.g., 43–75 ns at VCC = 6V/4.5V (CL = 50pF)-and retrigger time remains constant at ≤175 ns regardless of CX value. Reset recovery time is fixed at 5 ns across all operating voltages and temperatures.

Key Specifications

Pinout & Package

CD74HC4538ME4 is housed in a 16-pin SOIC (D) package, 7.5 mm × 10.3 mm footprint, 1.75 mm height, RoHS-compliant NIPDAU lead finish, MSL Level-1 (unlimited floor life).

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC4538ME4, CD74HC4538M96 offers identical performance in optimized SMT packaging, while CD74HC4538E provides the same timing behavior in a through-hole form factor-enabling design continuity across prototyping, qualification, and volume manufacturing phases.

Availability

CD74HC4538ME4 is available at Aetrix Electronics and suitable for industrial timing control, test equipment pulse generation, and power supply sequencing requiring stable component supply across extended temperature ranges and long product lifecycles.

Supply support for CD74HC4538ME4 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 50 years of innovation in high-reliability IC design.

The CD74HC4538ME4 belongs to TI's High-Speed CMOS Logic family, engineered for precision timing applications demanding predictable pulse generation, robust noise immunity, and operation across extreme environmental conditions.

FAQ

What is the minimum external timing resistor value supported by CD74HC4538ME4?

The CD74HC4538ME4 specifies a minimum external timing resistor RX of 5 kΩ. Using lower values risks exceeding the maximum allowable input current (30 mA into pins 2 or 14) and may degrade timing accuracy or cause device stress. For reliable operation with standard capacitors, RX should remain ≥5 kΩ across all operating conditions.

Can CD74HC4538ME4 operate with a 3.3V supply?

Yes, CD74HC4538ME4 supports 2V to 6V operation, making it fully compatible with 3.3V systems. At VCC = 3.3V, VIH is guaranteed ≥2.0V and VIL ≤1.0V, ensuring robust interfacing with common 3.3V microcontrollers and FPGAs without level translation.

How does the retriggerable mode function in CD74HC4538ME4?

In retriggerable mode, CD74HC4538ME4 extends the output pulse width by one full timing period (τ) upon each new trigger event-even if the previous pulse has not completed. This behavior is inherent to the internal circuitry and requires no external feedback; it enables dynamic pulse stretching in real-time control loops.

Is there a recommended decoupling capacitor for CD74HC4538ME4?

A 0.1 µF ceramic capacitor placed as close as possible to Pin 8 (VCC) and Pin 7 (GND) is recommended for CD74HC4538ME4. This minimizes supply noise coupling during output transitions and ensures stable timing performance, especially under fast-switching or high-current load conditions.

What is the maximum timing capacitor value usable with CD74HC4538ME4?

CD74HC4538ME4 does not specify a maximum CX value, but practical limits arise from leakage currents and board parasitics. For reliable operation, TI recommends keeping CX ≤ 10 µF and adding protection (e.g., 1N5395 diode) when CX ≥ 0.5 µF to prevent damage during rapid power-down events.