{"id":7976,"date":"2026-06-28T06:25:33","date_gmt":"2026-06-28T06:25:33","guid":{"rendered":"https:\/\/materialparts.com\/sn74ls42n\/"},"modified":"2026-06-28T11:44:53","modified_gmt":"2026-06-28T11:44:53","slug":"sn74ls42n","status":"publish","type":"post","link":"https:\/\/materialparts.com\/ar\/sn74ls42n\/","title":{"rendered":"SN74LS42N"},"content":{"rendered":"

\u0646\u0638\u0631\u0629 \u0639\u0627\u0645\u0629 \u0639\u0644\u0649 \u0627\u0644\u0645\u0646\u062a\u062c<\/h2>\n

The SN74LS42N from Texas Instruments is a 4-line BCD to 10-line decimal decoder with active-LOW outputs. It accepts a 4-bit BCD input and drives one of ten outputs LOW, while all invalid BCD codes (10-15) produce all outputs HIGH \u2014 making it both a decoder and a code validator in a 16-pin PDIP package.<\/p>\n

\u0627\u0644\u0645\u0648\u0627\u0635\u0641\u0627\u062a \u0627\u0644\u0631\u0626\u064a\u0633\u064a\u0629<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n
\u0627\u0644\u0648\u0638\u064a\u0641\u0629<\/td>\nBCD-to-decimal decoder (4-line to 10-line)<\/td>\n<\/tr>\n
\u0639\u0627\u0626\u0644\u0629 \u0627\u0644\u0645\u0646\u0637\u0642<\/td>\nLS (Low-power Schottky)<\/td>\n<\/tr>\n
\u062c\u0647\u062f \u0627\u0644\u0625\u0645\u062f\u0627\u062f<\/td>\n4.75V to 5.25V (5V nominal)<\/td>\n<\/tr>\n
Inputs<\/td>\nA0\u2013A3 (4-bit BCD)<\/td>\n<\/tr>\n
Outputs<\/td>\n0\u20139 (active LOW, mutually exclusive)<\/td>\n<\/tr>\n
Invalid Input Handling<\/td>\nAll outputs HIGH for BCD 10\u201315<\/td>\n<\/tr>\n
\u062a\u0623\u062e\u064a\u0631 \u0627\u0644\u0627\u0646\u062a\u0634\u0627\u0631<\/td>\n15\u201325ns typical<\/td>\n<\/tr>\n
Output Drive (IOL\/IOH)<\/td>\n8mA \/ -0.4mA<\/td>\n<\/tr>\n
Supply Current<\/td>\n7\u201313mA typical<\/td>\n<\/tr>\n
\u062f\u0631\u062c\u0629 \u062d\u0631\u0627\u0631\u0629 \u0627\u0644\u062a\u0634\u063a\u064a\u0644<\/td>\n0\u00b0C to +70\u00b0C<\/td>\n<\/tr>\n
\u0627\u0644\u062d\u0632\u0645\u0629<\/td>\nPDIP-16 (19.3 x 6.35mm)<\/td>\n<\/tr>\n<\/table>\n

\u0627\u0644\u0645\u064a\u0632\u0627\u062a<\/h2>\n
    \n
  • Decodes 4-bit BCD to one-of-ten active-LOW outputs<\/li>\n
  • All outputs HIGH for invalid input codes (10-15)<\/li>\n
  • Can serve as 3-line-to-8-line decoder (using A3 as enable)<\/li>\n
  • Can serve as 1-of-8 demultiplexer (A3 as data input)<\/li>\n
  • Input clamp diodes for simplified system design<\/li>\n<\/ul>\n

    \u0627\u0644\u062a\u0637\u0628\u064a\u0642\u0627\u062a<\/h2>\n
      \n
    • BCD-to-decimal decoding for displays<\/li>\n
    • Address decoding<\/li>\n
    • Code validation (reject invalid BCD)<\/li>\n
    • Demultiplexing<\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"

      Product Overview The SN74LS42N from Texas Instruments is a 4-line BCD to 10-line decimal decoder with active-LOW outputs. It accepts a 4-bit BCD input and drives one of ten outputs LOW, while all invalid BCD codes (10-15) produce all outputs HIGH \u2014 making it both a decoder and a code validator in a 16-pin PDIP […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[13,20],"tags":[],"chip_brand":[138],"class_list":["post-7976","post","type-post","status-publish","format-standard","hentry","category-integrated-circuits-ics","category-interface-ics","chip_brand-ti"],"acf":{"brief_explanation":"BCD-to-decimal decoder, 4-in\/10-out, active-LOW, invalid rejection, PDIP-16","date_code":"","package_case":"PDIP-16 (19.3 x 6.35 x 4.57mm, 2.54mm pitch, through-hole)","in_stock":3000,"datasheet":"https:\/\/www.ti.com\/lit\/ds\/symlink\/sn74ls42.pdf","price":"$1.929 @ 1ku","product_introduction":"The SN74LS42N from Texas Instruments is a BCD-to-decimal decoder that accepts a 4-bit BCD input on pins A0-A3 and activates (drives LOW) one of ten output lines (0-9). Unlike binary decoders like the 74LS138, the 7442 only decodes the ten valid BCD codes (0000-1001); for the six invalid codes (1010-1111), all outputs remain HIGH. This built-in code validation is useful in systems where invalid BCD data must not produce spurious outputs. The active-LOW outputs are compatible with most TTL active-LOW enable inputs, making the 7442 ideal for chip-select decoding. The device can also serve as a 3-line-to-8-line decoder by using A3 as an active-HIGH enable (when A3=LOW, outputs 0-7 decode A0-A2; when A3=HIGH, outputs 0-7 are all HIGH). As a demultiplexer, A3 becomes the data input: the data on A3 is routed to the selected output (0-7) in complemented form. The N suffix denotes the PDIP-16 through-hole package.","working_principle":"The SN74LS42N consists of eight inverters and ten 4-input NAND gates. The inverters generate both true and complement of each BCD input bit (A0-A3 and their complements). Each output NAND gate corresponds to one decimal digit and is driven by the combination of inputs that represents that digit in BCD. For example, output 5 (BCD 0101) is driven by a NAND gate with inputs A0, A2', A1, and A3'. When all four inputs are HIGH (meaning A0=1, A1=0, A2=1, A3=0, i.e., BCD=0101=5), the NAND output goes LOW. For invalid codes (10-15), the NAND gate combinations required don't exist in the decoder \u2014 none of the ten NAND gates have the correct input combination, so all outputs remain HIGH. As a 3-to-8 decoder: tie A3 LOW; A0-A2 select one of outputs 0-7 (LOW); outputs 8-9 always remain HIGH. As a demultiplexer: A3 is the data input; A0-A2 select the output; the selected output follows A3 (inverted), while all other outputs are HIGH.","pin_description":"\n
      Pin<\/th>Name<\/th>Type<\/th>Description<\/th><\/tr>\n
      1<\/td>0<\/td>Output<\/td>Output 0 (active LOW, for BCD 0000)<\/td><\/tr>\n
      2<\/td>1<\/td>Output<\/td>Output 1 (active LOW, for BCD 0001)<\/td><\/tr>\n
      3<\/td>2<\/td>Output<\/td>Output 2 (active LOW, for BCD 0010)<\/td><\/tr>\n
      4<\/td>3<\/td>Output<\/td>Output 3 (active LOW, for BCD 0011)<\/td><\/tr>\n
      5<\/td>4<\/td>Output<\/td>Output 4 (active LOW, for BCD 0100)<\/td><\/tr>\n
      6<\/td>5<\/td>Output<\/td>Output 5 (active LOW, for BCD 0101)<\/td><\/tr>\n
      7<\/td>6<\/td>Output<\/td>Output 6 (active LOW, for BCD 0110)<\/td><\/tr>\n
      8<\/td>GND<\/td>Power<\/td>Ground<\/td><\/tr>\n
      9<\/td>7<\/td>Output<\/td>Output 7 (active LOW, for BCD 0111)<\/td><\/tr>\n
      10<\/td>8<\/td>Output<\/td>Output 8 (active LOW, for BCD 1000)<\/td><\/tr>\n
      11<\/td>9<\/td>Output<\/td>Output 9 (active LOW, for BCD 1001)<\/td><\/tr>\n
      12<\/td>A3<\/td>Input<\/td>BCD input MSB<\/td><\/tr>\n
      13<\/td>A2<\/td>Input<\/td>BCD input bit 2<\/td><\/tr>\n
      14<\/td>A1<\/td>Input<\/td>BCD input bit 1<\/td><\/tr>\n
      15<\/td>A0<\/td>Input<\/td>BCD input LSB<\/td><\/tr>\n
      16<\/td>VCC<\/td>Power<\/td>Supply (5V)<\/td><\/tr>\n<\/table>","application_scenarios":"
        \n
      • BCD Decoding:<\/strong> Counter output (CD4510 or 74LS90) \u2192 A0-A3; selected output goes LOW; drives indicator LEDs (active LOW) or enable inputs of other ICs<\/li>\n
      • 3-to-8 Decoder:<\/strong> A3 tied LOW; A0-A2 select one of outputs 0-7; outputs 8-9 unused; acts like 74LS138 without enable inputs<\/li>\n
      • Code Validator:<\/strong> BCD data \u2192 A0-A3; if any output is LOW, the BCD is valid; if all outputs HIGH, the BCD is invalid (10-15); OR all outputs \u2192 active-HIGH error flag<\/li>\n
      • 1-of-8 Demux:<\/strong> Serial data on A3; A0-A2 select output; data appears (inverted) on selected output<\/li>\n<\/ul>","alternative_models":"\n
        Model<\/th>Manufacturer<\/th>Key Difference<\/th>Package<\/th>Supply<\/th><\/tr>\n
        74LS42N<\/td>TI\/Nexperia<\/td>Original TTL version with 5V-only supply, typical propagation delay 10-15ns<\/td>DIP-16<\/td>5V TTL<\/td><\/tr>\n
        74LS42D<\/td>TI\/Nexperia<\/td>Surface-mount SOIC version of LS with identical logic function<\/td>SOIC-16<\/td>5V TTL<\/td><\/tr>\n
        74HC42D<\/td>TI\/Nexperia<\/td>CMOS version with wide 2-6V supply range, lower power consumption and higher noise immunity<\/td>SOIC-16<\/td>2-6V CMOS<\/td><\/tr>\n
        74HC42N<\/td>TI\/Nexperia<\/td>Through-hole DIP version of HC family for prototyping and repair<\/td>DIP-16<\/td>2-6V CMOS<\/td><\/tr>\n
        74HCT42D<\/td>TI\/Nexperia<\/td>CMOS with TTL-compatible input levels, ideal for mixing with LS devices at 5V<\/td>SOIC-16<\/td>4.5-5.5V TTL-in<\/td><\/tr>\n
        74HCT42N<\/td>TI\/Nexperia<\/td>Through-hole DIP version of HCT family for prototyping and repair<\/td>DIP-16<\/td>4.5-5.5V TTL-in<\/td><\/tr>\n<\/table>\n

        The 7442 is a BCD-to-Decimal Decoder. Family variants span from the original LS TTL (5V only) to modern LVC\/AUP (down to 0.8V). HC and HCT versions offer 2-6V CMOS operation with HCT providing TTL-compatible input thresholds for mixed 5V systems. CD4000-series equivalents offer the widest 3-18V supply range at the cost of lower switching speed. DIP packages (N suffix) are through-hole; SOIC (D suffix) and TSSOP are surface-mount.<\/p>"},"_links":{"self":[{"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/posts\/7976","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/comments?post=7976"}],"version-history":[{"count":1,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/posts\/7976\/revisions"}],"predecessor-version":[{"id":8159,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/posts\/7976\/revisions\/8159"}],"wp:attachment":[{"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/media?parent=7976"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/categories?post=7976"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/tags?post=7976"},{"taxonomy":"chip_brand","embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/chip_brand?post=7976"}],"curies":[{"name":"\u062f\u0628\u0644\u064a\u0648 \u0628\u064a","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}