NXP Semiconductors N74F138N,602

Overview

N74F138N,602 from Philips Semiconductors is a 1-of-8 active-low decoder/demultiplexer in a 16-pin plastic DIP package, operating at 5V supply with typical propagation delay of 5.8 ns and supply current of 13 mA. It accepts three binary address inputs (A0–A2) and three enable inputs (E0, E1 low-active; E2 high-active), delivering eight mutually exclusive low-active outputs (Q0–Q7) for memory chip select decoding in industrial control systems.

For engineers reviewing the N74F138N,602 datasheet, N74F138N,602 pinout, N74F138N,602 application, or N74F138N,602 equivalent, key selection criteria include its TTL-compatible input thresholds (VIL = 0.8 V, VIH = 2.0 V), fan-out capability (50/33 high/low), industrial temperature range (–40°C to +85°C), and parallel expansion support for 1-of-32 decoding using four units and one inverter.

Technical Context

The N74F138N,602 implements combinational logic decoding with strict enable hierarchy: all outputs remain high unless E0 and E1 are simultaneously low and E2 is high. Its output structure is open-collector compatible with TTL loads, supporting up to 20 mA sink per output (IOL = 20 mA) and –1 mA source (IOH = –1 mA).

Propagation delays vary by signal path: 3.5–8.0 ns from address inputs (A0–A2) to outputs, 3.0–7.5 ns from E0/E1, and 3.5–9.5 ns from E2 - reflecting asymmetric internal gate structures optimized for enable-controlled demux operation rather than symmetric bidirectional switching.

Key Specifications

Pinout & Package

Package: 16-pin plastic dual in-line package (DIP), SOT38-4 footprint, 300 mil width, through-hole mount.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar decoder/demultiplexer applications.

Compared with SN74F138N and 74ACT138PC, the N74F138N,602 offers guaranteed industrial temperature operation and exact TTL interface compatibility - making it optimal for maintaining legacy 5 V systems, whereas SN74F138N provides second-source assurance, and 74ACT138PC introduces voltage flexibility at the cost of redesign effort.

Availability

N74F138N,602 is available at Aetrix Electronics and suitable for memory subsystem design, industrial I/O expansion, and legacy system repair requiring stable component supply and long-term industrial temperature qualification.

Supply support for N74F138N,602 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

Philips Semiconductors (now NXP Semiconductors) is a European semiconductor pioneer known for high-reliability logic families and industrial-grade analog products.

The 74F logic series - including the N74F138N,602 - was engineered for high-speed, low-power TTL-compatible operation in demanding industrial and telecom infrastructure applications.

FAQ

What is the maximum clock frequency supported by the N74F138N,602 in address decoding applications?

The N74F138N,602 does not operate on a clock; it is a combinational logic device. Its usable frequency limit is determined by propagation delay: with a typical tPD of 5.8 ns and worst-case 9.5 ns, it supports reliable decoding in systems with address setup/hold windows exceeding 10 ns - effectively enabling use in 50–100 MHz bus domains when paired with appropriate timing margins.

Can the N74F138N,602 be used as a demultiplexer, and how is the data input configured?

Yes, the N74F138N,602 can function as an 8-output demultiplexer. To do so, apply the data signal to one of the enable inputs (e.g., E0), hold the other two enables in their active states (E1 = low, E2 = high), and use A0–A2 as the 3-bit channel select. Each output Q0–Q7 then mirrors the data input in active-low form, synchronized to the address.

Is the N74F138N,602 pin-compatible with the 74LS138 and 74HC138?

The N74F138N,602 shares identical pinout and logic function with the 74LS138, enabling direct replacement in most 5 V TTL systems. However, it is not pin-compatible with the 74HC138 due to differing input thresholds (74HC requires VIL ≤ 1.5 V, VIH ≥ 3.5 V) and output drive strength - mixing them risks logic misstates or excessive loading.

What is the recommended decoupling for the N74F138N,602 in high-noise industrial environments?

Place a 100 nF ceramic capacitor between VCC (pin 16) and GND (pin 8), located within 5 mm of the package. For systems with multiple N74F138N,602 units, add a bulk 10 µF tantalum capacitor per power rail segment. This suppresses switching noise from simultaneous output transitions and maintains stable 5 V regulation during IOL surges up to 20 mA per output.

Does the N74F138N,602 support 3.3 V operation?

No, the N74F138N,602 is specified only for 4.5 V to 5.5 V operation. Applying 3.3 V violates the minimum VCC requirement and results in undefined output states, increased propagation delay, and potential failure to meet VIH/VIL thresholds. For 3.3 V systems, consider 74LVC138 or 74AHC138 instead.