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Texas Instruments SN74AHC138PW
- Part No.:
- SN74AHC138PW
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
SN74AHC138PW.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,438
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Product details
Overview
SN74AHC138PW from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in TSSOP-16 package, operating from 2 V to 5.5 V, with propagation delays as low as 5.7 ns at 5 V and ±25 mA output drive capability. It features three enable inputs (two active-low, one active-high) for cascading and demultiplexing, and is designed for high-speed memory decoding and data-routing applications.
For engineers reviewing the SN74AHC138PW datasheet, SN74AHC138PW pinout, SN74AHC138PW application, or SN74AHC138PW equivalent, this page delivers verified electrical specs, functional pin mapping, real-world use cases in memory systems and address decoding, and validated alternative options for design continuity.
Technical Context
The SN74AHC138PW implements positive-logic binary decoding with three address inputs (A0–A2) and three independent enables (G1, G2A, G2B), where only one of eight outputs (Y0–Y7) goes low when all enables are asserted. Its architecture supports direct demultiplexing by using an enable input as a data line.
It operates across industrial temperature range (−40°C to +85°C), meets JESD 17 latch-up immunity (>250 mA), and exceeds JESD 22 ESD ratings (2000 V HBM, 1000 V CDM), ensuring robustness in mixed-signal PCB environments with fast switching transients.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2 V to 5.5 V - supports dual-supply systems and interoperability with 3.3 V and 5 V logic families. |
| tPLH / tPHL (5 V) | 5.7 ns max (CL = 15 pF) - enables sub-10 ns system-level address decode timing in SRAM/Flash interfaces. |
| Output Drive | ±25 mA - sufficient to directly drive multiple CMOS inputs or small LED indicators without buffering. |
| Input Thresholds | VIH = 3.85 V, VIL = 1.65 V at VCC = 5.5 V - ensures noise margins >0.7 V under worst-case supply and temperature. |
| ICC (Quiescent) | 40 μA max at 5.5 V - enables low-static-power operation in battery-backed or always-on control logic. |
| ESD Rating | 2000 V HBM - meets IEC 61000-4-2 Level 2 for handling robustness during board assembly and field service. |
Pinout & Package
TSSOP-16 package (PW), 5.00 mm × 4.40 mm body size, 16-pin surface-mount with gull-wing leads; thermal pad not present (non-VQFN variant).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A2 | Address select inputs | Binary-coded 3-bit address determining active output Y0–Y7; TTL- and CMOS-compatible thresholds. |
| G1 | Enable input (active-high) | Primary global enable; when high and G2A/G2B low, decoder activates; used as data input in demux mode. |
| G2A, G2B | Enable inputs (active-low) | Two independent active-low enables allow hierarchical decoding or selective channel gating without external inverters. |
| Y0–Y7 | Active-low decoded outputs | Only one output asserts low per valid address/enable combination; open-drain behavior not supported - standard push-pull. |
| VCC, GND | Power and ground | Dedicated supply pins placed diagonally (Pin 16/VCC, Pin 8/GND) to minimize switching noise coupling in dense layouts. |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs | Enables 24-line decoding without external inverters and 32-line with only one inverter - reduces BOM count and layout area. |
| High-speed propagation | 5.7 ns max delay at 5 V allows integration into 100+ MHz address buses without adding pipeline stages. |
| Latch-up immunity | Exceeds 250 mA per JESD 17 - prevents destructive failure during transient overvoltage or hot-insertion events. |
| Wide VCC range | 2 V to 5.5 V operation supports legacy 5 V systems and modern 3.3 V/2.5 V domains on same board. |
| Low ICC | 40 μA max quiescent current enables use in power-sensitive microcontroller peripheral decoders. |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
Use Scenario: Selecting one of eight SRAM or Flash memory chips in a microcontroller-based embedded system with limited GPIO. IC Role / Device Role / Timing Role: Translates 3-bit chip-select bus into individual /CS lines; operates synchronously with address strobe to meet memory access setup/hold windows. Use Value: Eliminates need for discrete NAND gates or CPLD glue logic, reducing component count and routing complexity. | Use Scenario: Enabling specific UART, SPI, or ADC peripherals in a multi-interface IoT node based on processor address mapping. IC Role / Device Role / Timing Role: Acts as address-space router - A0–A2 map to peripheral ID, enables route data/control signals only to active device. Use Value: Ensures mutual exclusivity between peripherals sharing data bus, preventing contention and signal corruption. |
| LED Segment Driver Enable | Test Pattern Generator |
Use Scenario: Driving common-cathode 7-segment displays in multiplexed digital panel meters or industrial HMI units. IC Role / Device Role / Timing Role: Provides time-multiplexed segment activation via Y0–Y7 outputs; G1 accepts PWM-modulated enable for brightness control. Use Value: Delivers precise, glitch-free digit selection with <10 ns skew between outputs - critical for flicker-free display rendering. | Use Scenario: Generating deterministic 3-bit test vectors for boundary-scan or functional validation of FPGA I/O banks. IC Role / Device Role / Timing Role: Converts static control bits into parallel 8-channel stimulus patterns; enables/disable sequencing via G2A/G2B for state-controlled test phases. Use Value: Supports repeatable, synchronized assertion of up to eight DUT signals without software overhead or clock-domain crossing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 3-to-8 decoder applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LV138APWR | Lower VCC range (1.65–5.5 V); 10 ns max tPD at 3.3 V; higher input capacitance (4.5 pF vs. 2 pF). | Better suited for ultra-low-voltage 1.8 V systems; slightly slower but more noise-immune in noisy industrial settings. | Select when operating below 2 V or requiring enhanced noise rejection at cost of speed. |
| 74HC138D,653 | Same pinout and function; 12 ns max tPD at 4.5 V; wider industrial temp range (−40°C to +125°C); no JESD 22 CDM rating specified. | Preferred for automotive under-hood modules or extended-temp industrial controllers where reliability at high ambient dominates speed needs. | Choose for extended temperature operation where SN74AHC138PW's 85°C upper limit is insufficient. |
Compared with SN74LV138APWR and 74HC138D,653, the SN74AHC138PW delivers optimal balance of speed (5.7 ns), supply flexibility (2–5.5 V), and industrial-grade ESD/latch-up protection - making it the default choice for general-purpose high-speed decoding where 85°C operation suffices.
Availability
SN74AHC138PW is available at Aetrix Electronics and suitable for memory decoding, peripheral selection, LED multiplexing, and test pattern generation requiring stable component supply and guaranteed long-term sourcing.
Supply support for SN74AHC138PW includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and logic solutions with over 90 years of innovation in reliable, high-performance ICs.
The SNx4AHC138 product line was engineered for high-speed memory-decoding and data-routing applications demanding minimal propagation delay and robust cascading capability - targeting industrial control, communications infrastructure, and instrumentation systems.
FAQ
What is the maximum operating frequency supported by SN74AHC138PW?
The SN74AHC138PW does not specify a maximum clock frequency, as it is a combinational logic device. Its usable switching rate is determined by propagation delay: at 5 V and CL = 15 pF, tPLH/tPHL is 5.7 ns max, supporting effective address decode rates up to ~175 MHz in ideal conditions. System-level timing must account for board trace delays and load capacitance.
Can SN74AHC138PW be used as a demultiplexer?
Yes - the SN74AHC138PW functions as a 1-to-8 demultiplexer when one enable input (e.g., G1) is used as the data input while A0–A2 serve as select lines. With G2A and G2B held low, the selected Yx output mirrors the G1 logic state (active-low), enabling clean data distribution across eight channels.
Is SN74AHC138PW pin-compatible with older 74LS138 or 74HC138 devices?
Yes - SN74AHC138PW uses the industry-standard 16-pin TSSOP (PW) footprint and identical pinout to 74HC138 and 74LS138 in SOIC and TSSOP packages. However, voltage thresholds and drive strength differ: SN74AHC138PW supports 2–5.5 V operation and ±25 mA drive, unlike LS (5 V only, 8 mA) or HC (2–6 V, ±5.2 mA).
Does SN74AHC138PW require external pull-up resistors on its outputs?
No - SN74AHC138PW features push-pull outputs, not open-drain. Its Y0–Y7 outputs actively drive both high and low states. Pull-ups are unnecessary and would cause contention if connected, as the device sources/sinks current directly per its ±25 mA rating.
What is the thermal resistance (RθJA) of SN74AHC138PW in TSSOP package?
The junction-to-ambient thermal resistance (RθJA) for SN74AHC138PW in TSSOP-16 (PW) package is 135.9 °C/W, measured under standard JEDEC conditions (single-layer copper, 1-in² pad). This value assumes no thermal vias or enhanced PCB copper; actual performance improves with proper thermal land design per TI's layout guidelines.
SN74AHC138PW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHC
- Package/Case:
- 16-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- Decoder/Demultiplexer
- Circuit:
- 1 x 3:8
- Independent Circuits:
- 1
- Current - Output High, Low:
- 8mA, 8mA
- Voltage Supply Source:
- Single Supply
- Voltage - Supply:
- 2V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
SN74AHC138PW FAQ
1.How can I place an order for SN74AHC138PW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHC138PW on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for SN74AHC138PW reliable?
The price and inventory of SN74AHC138PW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHC138PW is usually 5 days.
3.What payment methods are accepted for SN74AHC138PW?
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4.How is shipping managed for SN74AHC138PW?
SN74AHC138PW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHC138PW order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for SN74AHC138PW?
For technical support, including SN74AHC138PW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHC138PW requirements.
6.How does Aetrix verify that SN74AHC138PW is sourced from the original manufacturer or authorized distributors?
All SN74AHC138PW products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SN74AHC138PW meets industry standards.
7.What is the process for return or replacement of SN74AHC138PW?
All SN74AHC138PW units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHC138PW, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The SN74AHC138PW part is unused and in its original packaging.
Return procedure for SN74AHC138PW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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