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SN74HC42 BCD-to-Decimal Decoder

Public Made by Adom

by adom

BCD-to-decimal (1-of-10) decoder with active-low outputs, 74HC CMOS.

logicdecoderbcd74hctisoic-16
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Contents

README

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SN74HC42

Texas Instruments · Decoder / Demultiplexer · SOIC-16

The SN74HC42 is a BCD-to-decimal decoder that takes a 4-bit BCD input and drives one of ten active-low outputs low, with invalid codes (10-15) leaving all outputs high. It is the 74HC-family equivalent of the classic 7442, used for 1-of-10 selection and display scanning.

Pinout

Pin Name Type Function
1 Y0 output Active-LOW decoded output for BCD input 0000. LOW when A3:A0 = 0; otherwise HIGH. LSTTL fan-out: 10 loads.
2 Y1 output Active-LOW decoded output for BCD input 0001.
3 Y2 output Active-LOW decoded output for BCD input 0010.
4 Y3 output Active-LOW decoded output for BCD input 0011.
5 Y4 output Active-LOW decoded output for BCD input 0100.
6 Y5 output Active-LOW decoded output for BCD input 0101.
7 Y6 output Active-LOW decoded output for BCD input 0110.
8 GND power_in Ground reference (0 V).
9 Y7 output Active-LOW decoded output for BCD input 0111.
10 Y8 output Active-LOW decoded output for BCD input 1000.
11 Y9 output Active-LOW decoded output for BCD input 1001.
12 A3 input BCD address input, bit 3 (MSB). HC: VIH ≥ 3.15 V @ VCC=4.5 V; VIL ≤ 1.35 V. HCT: VIH ≥ 2 V, VIL ≤ 0.8 V @ VCC=4.5-5.5 V. Input leakage ≤ 1 µA.
13 A2 input BCD address input, bit 2.
14 A1 input BCD address input, bit 1.
15 A0 input BCD address input, bit 0 (LSB).
16 VCC power_in Positive supply. HC: 2-6 V. HCT: 4.5-5.5 V. Absolute max −0.5 V to 7 V. Quiescent ICC ≤ 8 µA typ (80 µA max over temp).

Key specifications

Parameter Value
Type BCD-to-decimal (1-of-10) decoder
Logic family 74HC (CMOS)
Outputs 10, active-low
Supply voltage 2 V to 6 V
Propagation delay 20 ns typ at 5 V
Operating temperature -40 C to 85 C

Ordering variants

Same part, different packaging or reel option.

  • SN74HC42CD74HC42M
  • SN74HC42CD74HC42M.A
  • SN74HC42CD74HC42E
  • SN74HC42CD74HC42E.A
  • SN74HC42CD74HCT42E
  • SN74HC42CD74HCT42E.A
  • SN74HC42CD54HC42F3A
  • SN74HC42CD54HC42F3A.A

CAD (KiCad official)

  • Symbol: sn74hc42.kicad_sym
  • Footprint: sn74hc42.kicad_mod
  • 3D model: SOIC-16 body from KiCad Package_SO/SOIC-16_3.9x9.9mm_P1.27mm.
  • 3D model files: sn74hc42-etched.step / sn74hc42-etched.glb carry the MPN laser-etched on the die in a toggleable Adom.LaserEtch group (Fusion-ready); sn74hc42.step / sn74hc42.glb are the bare package body.

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

  • Datasheet: Texas Instruments datasheet (12 pp, sha256 adc98c4caa771189, retrieved 2026-08-17, tier: manufacturer)
  • Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
  • CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF