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74HC138N

3-to-8 decoder/demultiplexer, active-low outputs, 9ns, 16-PDIP

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制造商零件：

74HC138N

包装：

16-PDIP

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说明

产品概览

The 74HC138N from Texas Instruments is a 3-to-8 line decoder/demultiplexer. It decodes a 3-bit binary input to one of 8 mutually exclusive active-low outputs. With active-low enable inputs and 9ns propagation delay, it is essential for address decoding, chip-select generation, and data demultiplexing. Packaged in 16-PDIP.

主要规格

逻辑家族 74HC (High-Speed CMOS)
功能 3-to-8 line decoder/demultiplexer
Inputs 3 address (A0-A2) + 3 enable (E1, E2, E3)
Outputs 8 (active low, Y0-Y7)
传播延迟 9ns (typ at 4.5V)
电源电压 2V to 6V
包装 16-PDIP
工作温度 -40 to +85 C

特点

  • 3-to-8 line decoding
  • Active-low outputs for direct chip-select
  • Three enable inputs (2 active-low, 1 active-high)
  • Cascadable for larger decoding trees
  • 9ns propagation delay
  • Mutually exclusive outputs

应用

  • Memory address decoding
  • Chip-select generation for multiple peripherals
  • Data demultiplexing
  • I/O port expansion

The 74HC138N from Texas Instruments is a 3-to-8 line decoder/demultiplexer that takes a 3-bit binary address input and activates one of 8 active-low outputs. The three enable inputs (two active-low E1 and E2, one active-high E3) provide flexible cascading for larger decoding trees; all three must be in the enabled state for any output to be active. When enabled, the output corresponding to the binary address goes LOW while all other outputs remain HIGH. When disabled, all outputs go HIGH. This active-low output convention matches the active-low chip-select inputs of most memory and peripheral ICs, making the 74HC138 the standard address decoder in microprocessor systems. With 9ns propagation delay at 4.5V, it adds minimal delay to the address-to-chip-select path.

The 74HC138N uses internal AND-OR logic to decode the 3-bit address. The address inputs A0-A2 select one of 8 output lines. The enable logic requires E1=LOW, E2=LOW, and E3=HIGH for any output to be active. When enabled, the selected output Yn (where n = binary value of A2A1A0) goes LOW, while all other outputs remain HIGH. The three enable inputs serve different purposes in cascading: two 74HC138 devices can decode 4 bits (16 outputs) by connecting the MSB to one enable on each device. Similarly, four devices can decode 5 bits (32 outputs) using a fifth 74HC138 as a master decoder. The 9ns propagation delay is the time from address or enable input change to the corresponding output transition.

针脚 名称 功能
1 A0 Address input bit 0 (LSB)
2 A1 Address input bit 1
3 A2 Address input bit 2 (MSB)
4 E2 Enable input (active low)
5 E1 Enable input (active low)
6 E3 Enable input (active high)
7 Y7 Decoded output 7 (active low)
8 接地 地面
9 Y6 Decoded output 6
10 Y5 Decoded output 5
11 Y4 Decoded output 4
12 Y3 Decoded output 3
13 Y2 Decoded output 2
14 Y1 Decoded output 1
15 Y0 Decoded output 0
16 VCC Supply voltage (2-6V)
  • Memory address decoding with active-low chip-select for 8 peripheral devices
  • I/O port expansion using 3 MCU address lines to select 8 output channels
  • Cascaded 4-to-16 decoder using two 74HC138 devices
  • Data demultiplexing from one input to 8 output destinations
模型 制造商 主要区别
74HC139N TI Dual 2-to-4 decoder in one package
74HC154 TI 4-to-16 decoder, single device
74HCT138N TI TTL-compatible inputs (2-6V)
74LS138N TI Original TTL version, higher power
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Address: Room 2919, Guoli Building, Huaqiang North, Futian District, Shenzhen, Guangdong, China

 

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Contact Information

Email: info@materialparts.com

Tel / WhatsApp: +86 13760382860

服务与包装

Materialparts is a professional electronic component supplier based in Shenzhen, China, with over 20 years of global trading experience. We integrate component procurement, quality inspection, technical support, customized packaging, and global delivery services to provide one-stop supply chain solutions. Our business covers industrial control, automotive electronics, consumer electronics, medical devices and other industries. We always adhere to genuine sources, stable supply and considerate after-sales service.

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All products are sourced from official authorized channels and are 100% original genuine parts. Every batch of goods undergoes strict full-process quality inspection before delivery, with complete batch records and traceability documents provided. Our products comply with AEC-Q standards for automotive electronics and high-reliability specifications for medical devices. We eliminate counterfeits, refurbished parts and defective products from the source to secure your project production.

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Professional Packaging Standards

Electronic components are sensitive to static electricity, collision, moisture and dust. We adopt industry-standard anti-static packaging solutions to fully ensure the integrity of goods during transportation and storage.

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We provide value-added services including personalized packaging, custom labeling and re-reeling according to customer requirements, fully matching your production and warehouse management standards.

Contact Information

For service consultation or packaging customization, please feel free to contact us:
Email: info@materialparts.com
Tel / WhatsApp: +86 13760382860
Address: Room 2919, Guoli Building, Huaqiang North, Futian District, Shenzhen, Guangdong, China
 

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