Datasheet for the SM74HC138 3‑8 decoder, a high‑speed CMOS device with low power consumption and TTL‑compatible pins.
The SM74HC138 is a high‑speed CMOS 3‑to‑8 line decoder with three address inputs (A0‑A2) and eight active‑low outputs (Y0‑Y7). It includes three enable pins (E1‑E3) that must be set correctly for the outputs to become active. The device is intended for digital circuits and consumer‑electronics applications.
The document provides pin definitions, electrical characteristics such as supply voltage, input thresholds, output levels, and timing parameters, as well as package options (SOP16, TSSOP16, QFN16) and mechanical dimensions. This manual is written in Chinese.
| Supply voltage (absolute range) | -0.5 V to +7.0 V |
|---|---|
| Supply voltage (typical) | 3.0 V – 5.0 V |
| Power dissipation | < 400 mW |
| Operating temperature range | -40 °C to +80 °C |
| High‑level input voltage (VIH) | 3.0 V |
| Low‑level input voltage (VIL) | 2.0 V |
| High‑level output voltage (VOH) at VDD=5 V | 4.9 V |
| Low‑level output voltage (VOL) at VDD=5 V | 0.1 V |
| Static supply current (IDD) at VDD=6 V | 1 µA |
| Output high‑current drive (IOH) | -32 mA |
| Output low‑current drive (IOL) | 58 mA |
| Propagation delay (rise) tPLH | 19 ns |
| Propagation delay (fall) tPHL | 19 ns |
The device can operate with a supply voltage from –0.5 V up to +7.0 V.
A high input is recognized at 3.0 V (VIH) and a low input at 2.0 V (VIL) when VDD is 5 V.
The SM74HC138 works from –40 °C to +80 °C.
The high‑level output voltage is about 4.9 V and the low‑level output voltage is about 0.1 V.