Renesas 74HC4538P-E

Overview

74HC4538P-E from Renesas Electronics is a dual precision retriggerable/resettable monostable multivibrator in 16-pin DIP package, delivering 22 ns typical propagation delay (A/B to Q), 2–6 V operating voltage range, and pulse width programmability via external R/C networks. It serves as a timing generator in digital control systems requiring precise, repeatable one-shot pulses.

For engineers reviewing the 74HC4538P-E datasheet, 74HC4538P-E pinout, 74HC4538P-E application, or 74HC4538P-E equivalent, key selection criteria include retriggerable operation mode, dual independent monostable channels, clear-input reset capability, and compatibility with 74HC logic families across industrial temperature range (–40°C to +85°C).

Technical Context

The 74HC4538P-E implements two independent CMOS monostable multivibrators, each with separate A (rising-edge) and B (falling-edge) trigger inputs plus a dedicated active-low clear (CD) input. Its internal reference circuitry uses 1/3 VCC and 2/3 VCC thresholds to define discharge and charge phases of the external timing capacitor CX.

Each channel operates in retriggerable mode by default: a new trigger during an active output pulse extends the total pulse width. Pulse duration follows tw ≈ 0.7 × RX × CX, with stability maintained over –40°C to +85°C and supply voltages from 2 V to 6 V.

Key Specifications

Pinout & Package

Dual-in-line package (DILP-16), 7.62 mm pitch, 19.2 mm × 6.3 mm body size, through-hole mounting. RoHS-compliant Ni/Pd/Au plating.

Key Features

Applications

Equivalent & Alternatives

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

Compared with 74HC4538P-E, SN74HC4538N offers identical functionality and timing performance with seamless pin-to-pin compatibility, while MC74HC4538N provides functional equivalence at the cost of ~2 ns added propagation delay and ~20 µA higher standby current - both require no PCB changes but differ in manufacturer-specific reliability testing and qualification scope.

Availability

74HC4538P-E is available at Aetrix Electronics and suitable for industrial control panels, test instrumentation, power supply sequencing, and embedded timing modules requiring stable component supply and long-term manufacturability.

Supply support for 74HC4538P-E 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

Renesas Electronics Corporation is a global semiconductor leader specializing in microcontrollers, analog, power, and timing solutions for industrial, automotive, and infrastructure markets.

The HD74HC4538 product line delivers precision, retriggerable monostable timing for digital systems where predictable pulse generation, noise immunity, and wide supply voltage operation are essential - targeting legacy-compatible upgrades and cost-sensitive industrial controls.

FAQ

What is the maximum recommended timing capacitor value for stable operation of the 74HC4538P-E?

The 74HC4538P-E supports timing capacitors up to 1000000 pF (1 µF) with appropriate resistor selection. For reliable operation above 100 nF, use low-leakage film or ceramic capacitors and keep CX traces short with local VCC/GND decoupling. At 1 µF and 1 MΩ, pulse widths reach ~700 ms; verify timing accuracy against temperature drift and capacitor tolerance in final design.

Does the 74HC4538P-E support non-retriggerable mode, and how is it configured?

Yes, the 74HC4538P-E can operate in non-retriggerable mode by connecting the Q output back to the B input of the same channel. This configuration disables retriggering during an active pulse, causing subsequent triggers to be ignored until the current pulse completes. The datasheet Figure 4 shows this wiring; ensure external pull-up/pull-down resistors maintain valid logic levels on unused A/B inputs.

How does the clear (CD) input interact with ongoing timing cycles in the 74HC4538P-E?

The CD input is asynchronous and overrides all timing states: asserting CD low immediately forces QA and QB low, terminates any active pulse, and resets internal latches. CX rapidly charges to VCC via internal transistor M1, preparing the channel for the next trigger. This behavior is guaranteed across the full operating voltage and temperature range, making CD ideal for emergency stop or system reset functions.

Can the 74HC4538P-E drive LED loads directly, and what are the current limitations?

The 74HC4538P-E outputs can source/sink up to ±25 mA per pin (absolute max), but recommended steady-state drive is ≤4 mA for reliable fanout and thermal safety. Direct LED driving is feasible only with series resistors ≥1 kΩ at 5 V supply. For higher-current LEDs, use external buffer transistors or dedicated LED drivers - the 74HC4538P-E is optimized for logic-level timing, not power switching.

What is the impact of supply voltage variation on pulse width accuracy in the 74HC4538P-E?

Pulse width accuracy depends primarily on external R and C values, not VCC - the 0.7·R·C formula holds across 2–6 V due to internal threshold ratios fixed at ~1/3 and ~2/3 VCC. However, propagation delay varies with VCC (e.g., 47 ns max at 2 V vs. 40 ns at 6 V), so system-level timing budgets must account for voltage-dependent delays while pulse width remains stable.