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Texas Instruments SN74AHC138NSR
- Part No.:
- SN74AHC138NSR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74AHC138NSR.pdf
- Description:
- IC DECODER/DEMUX 1 X 3:8 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,900
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Product details
Overview
SN74AHC138NSR from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in SOP-16 package, operating from 2 V to 5.5 V, with propagation delays as low as 5.7 ns at 5 V and 15 pF load, designed for high-speed memory decoding and data routing in embedded control and industrial logic systems.
For engineers reviewing the SN74AHC138NSR datasheet, SN74AHC138NSR pinout, SN74AHC138NSR application, or SN74AHC138NSR equivalent, key selection criteria include enable-input architecture (two active-low, one active-high), output drive capability (±8 mA at 5 V), latch-up immunity (>250 mA), ESD robustness (2000 V HBM), and compatibility with 3.3 V/5 V mixed-signal interfaces.
Technical Context
The SN74AHC138NSR implements positive-logic binary decoding with three address inputs (A0–A2) and three enable inputs (G1, G2A, G2B), where two enables are active-low and one is active-high-enabling cascading without external inverters. Its function table defines eight mutually exclusive active-low outputs (Y0–Y7), each asserted only when all enables are satisfied and address matches.
It uses advanced CMOS AHC technology for rail-to-rail output swing, low static current (40 μA max ICC), and fast switching across supply range. Input transition rate limits (20 ns/V at 5 V) ensure reliable timing under fast-edge conditions, and thermal resistance (RθJA = 64 °C/W) supports operation up to +85 °C ambient in standard SOP layout.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2 V to 5.5 V - supports direct interface with both 3.3 V and 5 V logic families without level shifters |
| tPLH / tPHL (5 V, 15 pF) | 5.7 ns max - enables use in sub-100 MHz address decode paths with margin |
| IOL / IOH (5 V) | ±8 mA - drives standard TTL loads or multiple 74AHC inputs (fan-out ≥ 10) |
| VIH / VIL (5 V) | 3.85 V min / 1.65 V max - ensures noise margins >0.7 V in 5 V systems |
| ICC (5.5 V) | 40 μA max - enables low-power standby in battery-backed or energy-sensitive applications |
| ESD Rating (HBM) | 2000 V - meets IEC 61000-4-2 Level 2 for board-level handling robustness |
| Latch-up Immunity | >250 mA per JESD17 - prevents destructive latch-up during transient overvoltage events |
Pinout & Package
SOP-16 package (NS), body size 10.20 mm × 5.30 mm, 1.27 mm pitch, 2.00 mm max height, RoHS-compliant NiPdAu lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0, A1, A2 | Binary address inputs | Select one of eight outputs; logic levels directly map to Y0–Y7 activation per function table |
| G1 | Active-high enable | Must be HIGH for decoding; used with G2A/G2B to gate entire output bank |
| G2A, G2B | Active-low enables | Both must be LOW to activate outputs; simplifies cascading with no external inversion |
| Y0–Y7 | Active-low decoded outputs | Only one output LOW per valid address+enable combination; open-drain compatible with pull-up networks |
| VCC | Positive supply | Power rail for internal logic and output drivers; requires local 100 nF decoupling |
| GND | Ground reference | Return path for all input/output currents; must connect to low-impedance system ground plane |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables 24-line decoding without external inverters and 32-line with only one inverter - reduces BOM count and board area |
| High-speed propagation delay | 5.7 ns typical at 5 V/15 pF - minimizes added latency in memory access paths and real-time control loops |
| Rail-to-rail CMOS output swing | VOH ≥ 4.4 V and VOL ≤ 0.1 V at 5 V - ensures full logic-level compatibility with downstream 74AHC, 74LV, and microcontroller GPIOs |
| Low dynamic power consumption | Cpd = 13 pF - limits switching current and heat generation in high-frequency address bus applications |
| Robust input structure | Clamp diodes rated for ±20 mA - protects against overshoot/undershoot during hot-plug or signal integrity faults |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
Use Scenario: Selecting one of eight SRAM or flash memory chips in a microcontroller-based data acquisition system. IC Role / Device Role / Timing Role: 3-bit address decoder that asserts chip-select lines based on upper address bits and system enable signals. Use Value: Eliminates need for discrete gates or CPLDs, reducing latency by 5.7 ns versus alternative logic and enabling deterministic <100 ns memory access timing. | Use Scenario: Routing UART, SPI, or I²C peripherals to a shared bus in an industrial PLC backplane. IC Role / Device Role / Timing Role: Demultiplexer converting 3-bit peripheral ID into individual enable signals for isolated communication channels. Use Value: Enables hot-swappable peripheral modules with glitch-free selection via synchronized enable inputs, supporting modular firmware updates. |
| Bus Expansion Interface | Test Pattern Generator |
Use Scenario: Expanding a 16-bit data bus to control 8 independent LED driver ICs in an automotive lighting controller. IC Role / Device Role / Timing Role: Address-driven demux that activates one driver's OE pin while holding others inactive. Use Value: Provides deterministic, non-overlapping enable sequencing with <10 ns skew between outputs - prevents bus contention during state transitions. | Use Scenario: Generating 8-phase clock enables for boundary-scan test logic in FPGA-based prototyping platforms. IC Role / Device Role / Timing Role: Synchronized decoder triggered by JTAG TAP controller to assert test mode signals in rotating sequence. Use Value: Delivers precise, jitter-free phase alignment (≤1 ns inter-output skew) critical for IEEE 1149.1 compliance testing. |
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 |
|---|---|---|---|
| SN74HC138N | Slower propagation delay (21 ns @ 5 V), higher ICC (80 μA), HC logic family | Lower speed margin; suitable for <10 MHz systems with relaxed timing budgets | Choose when cost sensitivity outweighs performance needs and legacy HC footprint is required |
| 74LVC138AD,118 | Wider VCC range (1.65–5.5 V), lower tPD (4.2 ns @ 3.3 V), 3.3 V optimized | Better for mixed-voltage 1.8 V/3.3 V systems; not recommended for pure 5 V designs due to absolute max VI limit | Prefer for modern low-voltage embedded designs where 5 V tolerance is unnecessary |
Compared with SN74HC138N and 74LVC138AD,118, the SN74AHC138NSR delivers optimal balance of 5 V compatibility, sub-6 ns speed, and low-power AHC characteristics - making it the preferred choice for industrial control and legacy-compatible high-speed decoding where 5 V operation and timing margin are critical.
Availability
SN74AHC138NSR is available at Aetrix Electronics and suitable for industrial automation, embedded control, and test equipment requiring stable component supply with long-term manufacturability and RoHS-compliant packaging.
Supply support for SN74AHC138NSR 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 delivering analog, embedded processing, and logic solutions with emphasis on reliability, precision, and industrial-grade qualification.
The SN74AHC138NSR belongs to TI's AHC logic family, engineered for high-speed, low-power decoding in memory and data-routing applications where propagation delay, noise immunity, and supply voltage flexibility are design-critical.
FAQ
What is the maximum operating temperature for the SN74AHC138NSR?
The SN74AHC138NSR is rated for operation from −40 °C to +85 °C ambient temperature. This industrial temperature range ensures reliable performance in programmable logic controllers, motor drives, and factory automation equipment where thermal management is constrained. The SOP-16 package exhibits RθJA = 64 °C/W, allowing safe operation at full speed within this envelope when PCB copper area and airflow meet minimum guidelines.
Can the SN74AHC138NSR be used with a 3.3 V microcontroller driving its inputs?
Yes, the SN74AHC138NSR accepts 3.3 V logic inputs reliably: at VCC = 3.3 V, VIH is 2.1 V min and VIL is 0.9 V max, providing >1.2 V noise margin. Its AHC inputs have high impedance and low capacitance (Ci = 10 pF), minimizing loading on MCU GPIOs. Outputs swing rail-to-rail, so 3.3 V–driven SN74AHC138NSR outputs remain fully compatible with other 3.3 V logic devices.
How does the enable-input configuration of the SN74AHC138NSR simplify cascading?
The SN74AHC138NSR features two active-low enables (G2A, G2B) and one active-high enable (G1), allowing direct connection of outputs from a master decoder to enable inputs of slave devices without inverters. For example, a single SN74AHC138NSR can enable eight others to build a 24-line decoder - eliminating four external inverters and associated layout complexity versus HC-family alternatives.
Is the SN74AHC138NSR pin-compatible with older 74LS138 or 74HC138 packages?
Yes, the SN74AHC138NSR in SOP-16 (NS) shares identical pinout and footprint with SN74HC138N (PDIP), SN74HC138DR (SOIC), and industry-standard 74LS138 - including A0–A2, G1/G2A/G2B, Y0–Y7, VCC, and GND assignments. However, electrical behavior differs: AHC offers faster speed, lower power, and higher noise immunity than LS or HC, so timing and drive strength must be re-verified in legacy designs.
Does the SN74AHC138NSR require external pull-up resistors on its outputs?
No, the SN74AHC138NSR has push-pull CMOS outputs, not open-drain - so Y0–Y7 actively drive HIGH or LOW without external pull-ups. Each output sources/sinks ±8 mA at 5 V, sufficient to drive standard logic inputs or small LEDs (with series resistor). Pull-ups are only needed if interfacing with legacy TTL loads requiring stronger HIGH-side current, which is uncommon in modern AHC designs.
SN74AHC138NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHC
- Package/Case:
- 16-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- 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-SO
SN74AHC138NSR FAQ
1.How can I place an order for SN74AHC138NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHC138NSR 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 SN74AHC138NSR reliable?
The price and inventory of SN74AHC138NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHC138NSR is usually 5 days.
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SN74AHC138NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHC138NSR 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 SN74AHC138NSR?
For technical support, including SN74AHC138NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHC138NSR requirements.
6.How does Aetrix verify that SN74AHC138NSR is sourced from the original manufacturer or authorized distributors?
All SN74AHC138NSR 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 SN74AHC138NSR meets industry standards.
7.What is the process for return or replacement of SN74AHC138NSR?
All SN74AHC138NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHC138NSR, 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 SN74AHC138NSR part is unused and in its original packaging.
Return procedure for SN74AHC138NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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