\n| \u0627\u0644\u062d\u0632\u0645\u0629<\/td>\n | PDIP-16 (19.3 x 6.35mm, through-hole)<\/td>\n<\/tr>\n<\/table>\n\u0627\u0644\u0645\u064a\u0632\u0627\u062a<\/h2>\n\n- Three enable inputs for flexible cascading and demultiplexing<\/li>\n
- Active-low outputs simplify chip-select generation<\/li>\n
- Demultiplexing capability with data input on enable<\/li>\n
- Full decoding of input combinations (no don’t-care states)<\/li>\n
- Standard 74LS Schottky TTL technology<\/li>\n
- Multiple devices easily cascaded for larger decoding<\/li>\n
- Industry-standard pinout and function<\/li>\n
- Low 6.1mA typical supply current<\/li>\n<\/ul>\n
\u0627\u0644\u062a\u0637\u0628\u064a\u0642\u0627\u062a<\/h2>\n\n- Memory address decoding<\/li>\n
- I\/O port selection in microprocessor systems<\/li>\n
- Data demultiplexing and routing<\/li>\n
- Chip-select generation for multiple peripherals<\/li>\n
- Display digit selection<\/li>\n<\/ul>","protected":false},"excerpt":{"rendered":"
Product Overview The SN74LS138N is a 3-line to 8-line decoder\/demultiplexer from Texas Instruments with active-low outputs, three enable inputs, and 22ns typical propagation delay in a 16-pin PDIP through-hole package. Key Specifications Function 3-to-8 line decoder\/demultiplexer Select Inputs 3 (A, B, C) Outputs 8 (active low) Enable Inputs 3 (G1 active high, G2A and G2B […]<\/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-7845","post","type-post","status-publish","format-standard","hentry","category-integrated-circuits-ics","category-interface-ics","chip_brand-ti"],"acf":{"brief_explanation":"3-to-8 decoder\/demux, active-low outputs, 3 enable inputs, 22ns, PDIP-16","date_code":"","package_case":"PDIP-16 (19.3 x 6.35 x 4.57mm, 2.54mm pitch)","in_stock":15600,"datasheet":"https:\/\/www.ti.com\/lit\/ds\/symlink\/sn74ls138.pdf","price":"$0.68 @ 1ku","product_introduction":"The SN74LS138N is a 3-line to 8-line decoder\/demultiplexer from Texas Instruments in the 74LS Low-power Schottky TTL family. It decodes a 3-bit binary input (A, B, C) into one of eight mutually exclusive active-low outputs (Y0-Y7). Three enable inputs (G1 active high, G2A and G2B active low) provide flexible cascading for larger decoding functions and allow the device to be used as a 1-to-8 demultiplexer by applying data to an enable input. The 22ns typical propagation delay supports microprocessor clock rates up to tens of MHz. The PDIP-16 through-hole package is ideal for prototyping and educational applications.","working_principle":"The SN74LS138N uses AND-OR-INVERT logic to implement the 3-to-8 decoding function. The three select inputs (A, B, C) are decoded by eight 3-input AND gates, each producing one of the eight minterms. Each AND gate also includes the enable conditions: G1 must be high, and both G2A and G2B must be low for any output to be active. When enabled, exactly one of the eight outputs is driven low (active) corresponding to the binary value on the select inputs, while all other outputs remain high. When disabled (any enable condition not met), all outputs are forced high regardless of the select inputs. For demultiplexer operation, the data signal is applied to one of the enable inputs (typically G1), while the other enables are held in the active state. The data signal is then routed to the output selected by the A, B, C inputs. The 74LS Schottky TTL technology uses Schottky-clamped transistors to prevent saturation, reducing propagation delay to 22ns typical while maintaining reasonable power consumption at 6.1mA ICC.","pin_description":" \n| Pin<\/th> | Name<\/th> | Type<\/th> | Description<\/th><\/tr>\n |
|---|
| 1-3<\/td> | A, B, C<\/td> | Input<\/td> | Select inputs (A=LSB, C=MSB)<\/td><\/tr>\n | | 4-6<\/td> | G2A, G2B, G1<\/td> | Input<\/td> | Enable inputs (G2A, G2B active low; G1 active high)<\/td><\/tr>\n | | 7<\/td> | Y7<\/td> | Output<\/td> | Decoded output 7 (active low)<\/td><\/tr>\n | | 8<\/td> | GND<\/td> | Power<\/td> | Ground<\/td><\/tr>\n | | 9-11<\/td> | Y6-Y4<\/td> | Output<\/td> | Decoded outputs 6, 5, 4 (active low)<\/td><\/tr>\n | | 12-14<\/td> | Y3-Y1<\/td> | Output<\/td> | Decoded outputs 3, 2, 1 (active low)<\/td><\/tr>\n | | 15<\/td> | Y0<\/td> | Output<\/td> | Decoded output 0 (active low)<\/td><\/tr>\n | | 16<\/td> | VCC<\/td> | Power<\/td> | Supply voltage (5V)<\/td><\/tr>\n<\/table>","application_scenarios":"\n- Memory Decoding:<\/strong> 3 select inputs decode 8 memory banks; active-low outputs directly drive chip-enable pins on SRAM and EPROM<\/li>\n
- I\/O Port Selection:<\/strong> Decodes microprocessor address lines to select one of eight I\/O ports or peripheral chips<\/li>\n
- Data Demultiplexing:<\/strong> Data applied to G1 is routed to the output selected by A, B, C for serial-to-parallel distribution<\/li>\n
- Cascaded Decoding:<\/strong> Two 74LS138 devices cascade to form a 4-to-16 decoder using enable inputs for the MSB<\/li>\n
- Display Multiplexing:<\/strong> Active-low outputs select one of eight digit drivers in multiplexed LED displays<\/li>\n<\/ul>","alternative_models":"
\n| Model<\/th> | Manufacturer<\/th> | Key Difference<\/th> | Package<\/th> | Supply<\/th><\/tr>\n |
|---|
| 74LS138N<\/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 | | 74LS138D<\/td> | TI\/Nexperia<\/td> | Surface-mount SOIC version of LS with identical logic function<\/td> | SOIC-16<\/td> | 5V TTL<\/td><\/tr>\n | | 74HC138D<\/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 | | 74HC138N<\/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 | | 74HCT138D<\/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 | | 74HCT138N<\/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 | | 74AC138D<\/td> | TI\/Nexperia<\/td> | Advanced CMOS with 2-6V supply and higher output drive current (24mA vs 6mA for HC)<\/td> | SOIC-16<\/td> | 2-6V CMOS<\/td><\/tr>\n | | 74AC138N<\/td> | TI\/Nexperia<\/td> | Through-hole DIP version of AC family for prototyping and repair<\/td> | DIP-16<\/td> | 2-6V CMOS<\/td><\/tr>\n | | 74LVC138D<\/td> | TI\/Nexperia<\/td> | Low-voltage CMOS for 1.65-3.6V modern logic with 24mA output drive and bus-hold inputs<\/td> | SOIC-16<\/td> | 1.65-3.6V CMOS<\/td><\/tr>\n | | 74LVC138N<\/td> | TI\/Nexperia<\/td> | Through-hole DIP version of LVC family for prototyping and repair<\/td> | DIP-16<\/td> | 1.65-3.6V CMOS<\/td><\/tr>\n<\/table>\n The 74138 is a 3-Line to 8-Line Decoder\/Demultiplexer. 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\/7845","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=7845"}],"version-history":[{"count":1,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/posts\/7845\/revisions"}],"predecessor-version":[{"id":8211,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/posts\/7845\/revisions\/8211"}],"wp:attachment":[{"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/media?parent=7845"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/categories?post=7845"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/tags?post=7845"},{"taxonomy":"chip_brand","embeddable":true,"href":"https:\/\/materialparts.com\/ar\/wp-json\/wp\/v2\/chip_brand?post=7845"}],"curies":[{"name":"\u062f\u0628\u0644\u064a\u0648 \u0628\u064a","href":"https:\/\/api.w.org\/{rel}","templated":true}]}} | | |