Nexperia USA Inc. 74HCT238DB,112

Overview

74HCT238DB,112 from Nexperia is a 3-to-8 line decoder/demultiplexer with TTL-compatible inputs, active-HIGH mutually exclusive outputs (Y0–Y7), three enable inputs (E1, E2 active LOW; E3 active HIGH), and operation across 4.5 V to 5.5 V supply. It supports memory chip select decoding and parallel expansion to 1-of-32 via four ICs plus one inverter, with propagation delay as low as 18 ns at VCC = 4.5 V and CL = 15 pF.

For engineers reviewing the 74HCT238DB,112 datasheet, 74HCT238DB,112 pinout, 74HCT238DB,112 application, or 74HCT238DB,112 equivalent, key selection considerations include TTL-level input compatibility, 3-enable logic for hierarchical decoding, SO16 package thermal derating (12.4 mW/K above 110 °C), -40 °C to +125 °C operating range, and demultiplexing capability using E1/E2 as strobes and E3 as data input.

Technical Context

The device implements combinational logic decoding of three binary address inputs (A0–A2) into eight active-HIGH outputs, where only one output is HIGH when all enables satisfy E1 = LOW, E2 = LOW, and E3 = HIGH. Its triple-enable architecture enables cascading without external logic-E1 and E2 serve as group selects while E3 acts as global enable or data path control in demux mode.

Input clamping diodes allow interfacing to voltages exceeding VCC when used with current-limiting resistors. Static characteristics confirm VIH = 2.0 V (min) and VIL = 0.8 V (max) at VCC = 4.5–5.5 V, ensuring robust noise immunity and compatibility with standard TTL logic families.

Key Specifications

Pinout & Package

74HCT238DB,112 is supplied in SO16 (SOT109-1) plastic small outline package: 16-pin, 3.9 mm body width, 1.27 mm lead pitch, with gull-wing leads and moisture sensitivity level (MSL) 1 per JEDEC J-STD-020.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 3-to-8 decoder applications.

Compared with 74HC238DB,112 and SN74LS238N, the 74HCT238DB,112 uniquely balances TTL input compatibility with industrial temperature range and low quiescent current-making it optimal for new designs bridging legacy and modern logic families.

Availability

74HCT238DB,112 is available at Aetrix Electronics and suitable for memory decoding, microcontroller peripheral expansion, industrial PLC I/O addressing, and legacy bus interface logic requiring stable component supply across extended temperature ranges.

Supply support for 74HCT238DB,112 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

Nexperia is a leading semiconductor manufacturer specializing in high-performance, reliable logic, analog, and discrete components for industrial, automotive, and consumer applications.

The 74HCT238 belongs to Nexperia's 74HCT logic family-designed specifically to provide TTL-compatible input thresholds with CMOS power efficiency for seamless integration into mixed-technology digital systems.

FAQ

What is the maximum clock frequency supported by the 74HCT238DB,112?

The 74HCT238DB,112 is a combinational decoder-not a clocked device-so it has no defined clock frequency. Its speed is characterized by propagation delay: 18 ns typical from address input to output at VCC = 4.5 V and CL = 15 pF. This supports reliable operation in systems with address valid times ≥ 25 ns, such as 8-bit MCUs running at ≤ 20 MHz bus clocks.

Can the 74HCT238DB,112 be used as a demultiplexer, and how is it configured?

Yes-it functions as an 1-to-8 demultiplexer by using E3 as the data input (HIGH/LOW determines output state) and E1/E2 as strobe controls. When E1 and E2 are LOW, the data on E3 appears inverted on the selected Yx output (since Yx is active HIGH and enabled only when E3 is HIGH). This configuration requires no external components and maintains full timing specifications.

Does the 74HCT238DB,112 require pull-up or pull-down resistors on its enable inputs?

No-enable inputs E1 and E2 have built-in clamp diodes and TTL-compatible thresholds, allowing direct connection to MCU GPIOs or other logic outputs. However, if left unconnected, E1 and E2 must be held LOW (via MCU output or resistor) to avoid floating states that disable all outputs; E3 must be held HIGH for normal decode operation.

How does the SO16 package (SOT109-1) of the 74HCT238DB,112 handle thermal dissipation?

The SO16 package has a total power dissipation limit of 500 mW at T_amb ≤ 110 °C, derating linearly by 12.4 mW/K above that temperature. At maximum rated ambient (+125 °C), usable power drops to ~310 mW. Layout best practices include a minimum 25 mm² copper pour connected to pin 8 (GND) and pin 16 (VCC) to enhance heat spreading and stabilize switching performance.