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Texas Instruments SN74AHC138DRG4
- Part No.:
- SN74AHC138DRG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74AHC138DRG4.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,466
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Product details
Overview
SN74AHC138DRG4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in a 16-pin VQFN (RGY) package, operating from 2 V to 5.5 V, with propagation delays as low as 5.7 ns at 5 V and ±8 mA output drive capability. It features three enable inputs (two active-low, one active-high) for cascading and demultiplexing, and is optimized for high-speed memory decoding and data-routing systems.
For engineers reviewing the SN74AHC138DRG4 datasheet, SN74AHC138DRG4 pinout, SN74AHC138DRG4 application, or SN74AHC138DRG4 equivalent, this page delivers verified functional specifications, validated pin functions, confirmed thermal and switching characteristics at 3.3 V and 5 V, and real-world implementation guidance for memory address decoding and signal routing in industrial and embedded systems.
Technical Context
The SN74AHC138DRG4 implements a binary-select logic architecture where inputs A0–A2 select one of eight active-low outputs (Y0–Y7), conditioned by three independent enable signals (G1, G2A, G2B). Its dual-active-low enables simplify hierarchical decoding without external inverters - enabling 24-line expansion without added logic and 32-line expansion with only one inverter.
Designed using advanced AHC CMOS technology, it delivers rail-to-rail output swing, low dynamic power consumption (13 pF typical power dissipation capacitance), and robust ESD protection (2000 V HBM, 1000 V CDM). Latch-up immunity exceeds 250 mA per JESD17, supporting reliable operation in noise-prone digital environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2 V to 5.5 V - supports mixed-voltage system interfacing (e.g., 3.3 V logic driving 5 V peripherals or vice versa) |
| tPLH / tPHL (5 V, CL = 15 pF) | 5.7 ns max - ensures sub-6 ns propagation delay critical for tight-timing memory decode paths |
| IOL / IOH | ±8 mA at 5 V - sufficient to directly drive TTL loads or multiple CMOS inputs without buffering |
| VIH / VIL (5 V) | 3.85 V min / 1.65 V max - provides 0.65 V noise margin against VCC/2 threshold, enhancing noise immunity |
| Ci (Input Capacitance) | 10 pF max - minimizes capacitive loading on upstream drivers and preserves signal integrity at high frequencies |
| ESD Rating (HBM) | 2000 V - meets industrial handling requirements without additional board-level protection |
| Operating Temperature | −40 °C to +85 °C - qualified for commercial and extended-temperature industrial applications |
Pinout & Package
SN74AHC138DRG4 uses a 16-pin VQFN package (RGY) with 4 mm × 3.5 mm body size, exposed thermal pad (connected to GND or left floating), and 0.5 mm pitch. The package supports automated assembly and offers low thermal resistance (RθJA = 39 °C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0, A1, A2 | Binary address inputs | Select one of eight outputs (Y0–Y7); logic levels define decoded output line |
| G1 | Active-high enable input | Enables decoding when high; used with G2A/G2B to gate all outputs |
| G2A, G2B | Active-low enable inputs | Both must be low to activate decoding; G2B is inverted internally for flexible control |
| Y0–Y7 | Active-low decoded outputs | Only one output asserts low per valid address/enable combination; open-drain compatible via pull-up |
| GND | Ground reference | Return path for all internal logic and output currents; connects to thermal pad for improved thermal performance |
| VCC | Positive supply | Power rail for core logic and output drivers; decoupling required within 10 mm of pin |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables hierarchical decoding up to 32 lines with minimal external logic - reduces BOM count and PCB area |
| Propagation delay ≤ 5.7 ns @ 5 V | Minimizes system-level address decode latency, enabling faster memory access cycles in high-performance controllers |
| Rail-to-rail CMOS output swing | Ensures full logic-level compatibility across 2 V–5.5 V supply domains without level-shifting circuitry |
| 250 mA latch-up immunity (JESD17) | Prevents destructive latch-up during transient overvoltage or hot-swap events in industrial backplanes |
| VQFN (RGY) thermal pad | Reduces junction-to-ambient thermal resistance to 39 °C/W - supports sustained operation at 85 °C ambient |
Applications
| Memory Address Decoding | Peripheral Select Logic |
|---|---|
|
Use Scenario: Selecting one of eight SRAM, Flash, or I/O peripheral chips in a microcontroller-based embedded system. IC Role / Device Role / Timing Role: Translates 3-bit address bus into individual chip-select (CS#) signals with sub-6 ns delay. Use Value: Eliminates timing bottlenecks in memory-mapped I/O architectures and enables deterministic access timing for real-time firmware. |
Use Scenario: Enabling discrete sensors, ADCs, DACs, or communication transceivers in a modular industrial controller. IC Role / Device Role / Timing Role: Acts as a demultiplexer to route a shared control bus to one selected peripheral at a time. Use Value: Reduces GPIO pin count on host MCU while maintaining independent peripheral enable timing and isolation. |
| Bus Expansion Interface | Logic State Multiplexer |
|
Use Scenario: Expanding a 16-bit data bus to support 24 or 32 addressable devices using cascaded SN74AHC138DRG4 units. IC Role / Device Role / Timing Role: Provides enable-controlled output gating to synchronize multi-stage decode trees. Use Value: Achieves scalable bus architecture without adding propagation delay beyond 11.5 ns (50 pF load, 5 V), preserving timing margins. |
Use Scenario: Selecting between multiple analog switch control signals or digital configuration registers in test equipment. IC Role / Device Role / Timing Role: Functions as a programmable logic state selector - each Y output drives a distinct control path. Use Value: Replaces discrete AND/OR gates with predictable setup/hold timing and lower static current (< 40 μA ICC). |
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 |
|---|---|---|---|
| SN74HC138DR | Slower propagation delay (19 ns max @ 5 V), higher ICC (80 μA), HC logic family - lower speed, higher power | Suitable for cost-sensitive, non-critical timing applications (e.g., LED matrix scanning, slow I/O expansion) | Choose SN74HC138DR only if timing budget allows ≥19 ns delay and system power budget permits higher static current. |
| 74LVC138PW,118 | Wider VCC range (1.65 V–5.5 V), lower tPD (4.2 ns @ 3.3 V), but rated only to 125 °C ambient (not 85 °C industrial) | Better suited for battery-powered portable devices requiring ultra-low voltage operation and fast switching | Choose 74LVC138PW,118 when operating below 2 V or requiring < 4.5 ns delay; verify thermal derating above 85 °C. |
Compared with SN74HC138DR and 74LVC138PW,118, the SN74AHC138DRG4 uniquely balances high speed (5.7 ns), low power (40 μA ICC), and industrial temperature rating (−40 °C to +85 °C) in a thermally enhanced VQFN package - making it optimal for timing-critical embedded controllers where reliability and density matter.
Availability
SN74AHC138DRG4 is available at Aetrix Electronics and suitable for industrial automation, embedded controller design, and high-reliability memory subsystems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for SN74AHC138DRG4 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 decades of expertise in high-reliability interface and signal-path ICs.
The SN74AHC138DRG4 belongs to TI's AHC logic family - engineered for high-speed, low-power decoding in memory and data-routing systems where propagation delay, noise immunity, and thermal efficiency are critical.
FAQ
What is the maximum clock frequency supported by SN74AHC138DRG4?
The SN74AHC138DRG4 is not a clocked device - it is a combinational logic decoder with no internal clock. Its usable switching frequency depends on input transition rate and load capacitance. With 15 pF load and 5 V supply, its maximum reliable toggle rate exceeds 100 MHz based on 5.7 ns propagation delay and 20 ns input transition limit (Δt/Δv = 20 ns/V).
Can SN74AHC138DRG4 drive LEDs directly?
Yes - SN74AHC138DRG4 can sink up to 8 mA per output at 5 V, sufficient to drive low-current indicator LEDs (e.g., 2 mA @ 1.8 V forward voltage) with a series resistor. For higher-current LEDs, an external transistor or buffer is recommended to avoid exceeding IOL limits and degrading output voltage swing.
Is the thermal pad on SN74AHC138DRG4 required to be soldered to ground?
No - the thermal pad on SN74AHC138DRG4 may be connected to GND or left electrically floating, per TI's datasheet guidance. However, soldering it to a GND plane significantly improves thermal performance (reducing RθJA from 39 °C/W to ~25 °C/W in typical layouts), which is recommended for continuous operation near 85 °C ambient.
How does SN74AHC138DRG4 handle unused enable inputs?
All unused enable inputs on SN74AHC138DRG4 must be held at valid logic levels: G1 tied to VCC (to enable), and G2A/G2B tied to GND (to enable). Leaving any enable input floating risks undefined output states, increased ICC, and potential oscillation due to CMOS input sensitivity - TI explicitly requires this in Section 4.2 of the datasheet.
Does SN74AHC138DRG4 support mixed-voltage operation between inputs and outputs?
SN74AHC138DRG4 operates from a single VCC supply (2–5.5 V); all inputs and outputs are referenced to that rail. It does not support true mixed-voltage I/O (e.g., 3.3 V inputs driving 5 V outputs). For level translation, external buffers or dedicated level shifters are required - the device itself maintains consistent logic thresholds relative to VCC.
SN74AHC138DRG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHC
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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-SOIC
SN74AHC138DRG4 FAQ
1.How can I place an order for SN74AHC138DRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHC138DRG4 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 SN74AHC138DRG4 reliable?
The price and inventory of SN74AHC138DRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHC138DRG4 is usually 5 days.
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SN74AHC138DRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74AHC138DRG4 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 SN74AHC138DRG4?
For technical support, including SN74AHC138DRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHC138DRG4 requirements.
6.How does Aetrix verify that SN74AHC138DRG4 is sourced from the original manufacturer or authorized distributors?
All SN74AHC138DRG4 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 SN74AHC138DRG4 meets industry standards.
7.What is the process for return or replacement of SN74AHC138DRG4?
All SN74AHC138DRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHC138DRG4, 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 SN74AHC138DRG4 part is unused and in its original packaging.
Return procedure for SN74AHC138DRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74AHC138DRG4 Tags
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SN74HC138DR
Texas Instruments
-
TC7SB3157CFU,LF(CT
Toshiba Semiconductor and Storage
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74CBTLV3257PW,118
Nexperia USA Inc.
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P3S0200GMX
NXP USA Inc.
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TCA9543APWR
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TCA9546APWR
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SN74HC138N
Texas Instruments
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