Texas Instruments CD74HC4538PWRG4

Overview

CD74HC4538PWRG4 from Texas Instruments is a dual retriggerable/resettable monostable multivibrator IC used for precision timing in digital systems. It delivers independent trigger/reset propagation delays (e.g., 50 ns at 4.5 V), Schmitt-trigger inputs on A/B terminals, buffered Q/Q̅ outputs, and supports external timing via RX/CX components to generate pulse widths from microseconds to milliseconds. It operates across -55°C to +125°C in industrial control and test equipment.

For engineers reviewing the CD74HC4538PWRG4 datasheet, CD74HC4538PWRG4 pinout, CD74HC4538PWRG4 application, or CD74HC4538PWRG4 equivalent, key selection criteria include retriggerable mode operation, edge-selectable triggering (A = leading, B = trailing), wide VCC range (2–6 V), LSTTL fanout capability (10 loads), and TSSOP-16 packaging for high-density PCB layouts.

Technical Context

The CD74HC4538PWRG4 implements two independent monostable circuits with separate A/B trigger inputs and R reset inputs per section. Each section uses an external resistor (RX) and capacitor (CX) to define output pulse width τ ≈ 0.7·RX·CX, with propagation delays from A/B or R to Q/Q̅ fully independent of RX/CX values.

Its Schmitt-trigger inputs provide noise immunity (NIH/NIL = 30% of VCC at 5 V), and it supports both retriggerable and non-retriggerable modes via internal feedback configuration. The device features balanced rise/fall times (15 ns typical at 4.5 V, CL = 15 pF) and operates reliably under rapid power-down conditions when protected per Figure 12/13.

Key Specifications

Pinout & Package

TSSOP-16 package (PW), 4.4 mm × 5.0 mm footprint, 1.2 mm max height, 0.65 mm lead pitch, RoHS-compliant NIPDAU finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with CD74HC4538M96 and CD74HCT4538PWR, the CD74HC4538PWRG4 provides optimal thermal performance in space-constrained TSSOP layouts while maintaining full compatibility with modern 3.3 V/5 V mixed-signal systems - making it the preferred choice for new industrial controller designs.

Availability

CD74HC4538PWRG4 is available at Aetrix Electronics and suitable for industrial automation, test instrumentation, and aerospace timing applications requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for CD74HC4538PWRG4 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 delivering analog, embedded processing, and logic solutions with emphasis on reliability, precision, and energy efficiency.

The CD74HC4538PWRG4 belongs to TI's High-Speed CMOS Logic family, designed specifically for robust, low-power timing functions in harsh-environment digital systems where deterministic pulse generation and noise immunity are critical.

FAQ

What is the minimum external timing capacitor value supported by CD74HC4538PWRG4?

The CD74HC4538PWRG4 supports CX = 0 pF minimum per datasheet Section "Operating Conditions". In practice, a small capacitor (e.g., 10–100 pF) is recommended to stabilize timing against parasitic capacitance and improve pulse width consistency across voltage and temperature.

Can CD74HC4538PWRG4 operate reliably at 2.0 V supply voltage?

Yes, CD74HC4538PWRG4 is fully specified down to 2.0 V VCC. At this voltage, propagation delay increases to 250 ns max (A/B → Q), and output drive strength reduces, but all logic thresholds, Schmitt hysteresis, and timing functionality remain guaranteed across -55°C to +125°C.

How does the retriggerable mode function differ from non-retriggerable mode in CD74HC4538PWRG4?

In retriggerable mode, each new trigger extends the output pulse by full τ from that edge; in non-retriggerable mode, only the first trigger starts the timer. CD74HC4538PWRG4 achieves non-retriggerable operation by connecting Q to B (for A-triggered) or Q to A (for B-triggered), as defined in Functional Terminal Connections.

Is CD74HC4538PWRG4 pin-compatible with CD74HC4538PWR?

Yes, CD74HC4538PWRG4 and CD74HC4538PWR share identical TSSOP-16 pinout, electrical specifications, and marking (HJ4538). The "G4" suffix denotes green/RoHS-compliant packaging and tape-and-reel packaging (2000 pcs/reel), with no functional or mechanical differences.

What protection is required for CD74HC4538PWRG4 when using CX ≥ 0.5 µF?

When CX ≥ 0.5 µF, rapid power-down may discharge stored energy into pins 2 or 14. TI recommends either a 1 A protection diode (e.g., 1N5395) between CX and ground with separate ground return, or a 51 Ω series current-limiting resistor - both detailed in Figures 12 and 13 of the CD74HC4538PWRG4 datasheet.