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Texas Instruments SN74AHCT138PWRG4
- Part No.:
- SN74AHCT138PWRG4
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
SN74AHCT138PWRG4.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,587
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Product details
Overview
SN74AHCT138PWRG4 from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in TSSOP-16 package, operating at 1.5–5.5 V supply, with TTL-compatible inputs, 12 ns max propagation delay (CL = 15 pF), and ±8 mA output drive-designed for high-speed memory decoding and address demultiplexing in industrial control and embedded microcontroller systems.
For engineers reviewing the SN74AHCT138PWRG4 datasheet, SN74AHCT138PWRG4 pinout, SN74AHCT138PWRG4 application, or SN74AHCT138PWRG4 equivalent, this page delivers verified electrical specs, functional mode details, real-world use cases, and validated alternative options for system-level timing and address routing decisions.
Technical Context
The SN74AHCT138PWRG4 implements positive-logic 3-to-8 decoding with three enable inputs (G1 active-high; G2A/G2B active-low), enabling cascaded 24-line or 32-line decoding without external inverters. Its architecture supports both decoder and demultiplexer modes-where an enable input doubles as data input for 1-to-8 signal distribution.
It features TTL-voltage compatible inputs (VIH = 2 V min, VIL = 0.8 V max), rail-to-rail CMOS outputs, latch-up immunity >250 mA per JESD17, and ESD protection per JESD22 (±2000 V HBM, ±1000 V CDM). Propagation delays are specified across temperature (−40°C to +85°C) and load (15 pF / 50 pF).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 1.5 V to 5.5 V - supports mixed-voltage system interfacing (e.g., 3.3 V MCU driving 5 V peripherals) |
| Propagation Delay (tPLH/tPHL) | 1 ns (min) to 12 ns (max) at CL = 15 pF - enables sub-100 MHz address decoding in memory subsystems |
| Output Drive Strength | ±8 mA at VCC = 5 V - sufficient to directly drive multiple 74-series inputs or small LED loads without buffers |
| Input Compatibility | TTL-level thresholds (VIH ≥ 2 V, VIL ≤ 0.8 V) - ensures reliable interfacing with legacy 5 V logic families |
| Operating Temperature | −40°C to +85°C - qualified for industrial-grade embedded applications including PLC I/O modules |
| Power Dissipation Capacitance | 14 pF - enables accurate dynamic power estimation in high-frequency switching scenarios |
Pinout & Package
TSSOP-16 (PW) package: 5.0 mm × 6.4 mm body size, 0.65 mm lead pitch, exposed thermal pad not present (non-RGY variant); RoHS-compliant, NIPDAU/SN lead finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A, B, C | Binary select inputs | 3-bit address lines determining active output Y0–Y7; decoded in positive logic |
| G1 | Active-high enable | Primary chip-select; all outputs HIGH when G1 = LOW (disabled state) |
| G2A, G2B | Active-low enables | Secondary enables; both must be LOW for decode operation - simplifies hierarchical addressing |
| Y0–Y7 | Active-low decoded outputs | Only one output goes LOW per valid input combination; all others remain HIGH |
| VCC, GND | Power terminals | Single 1.5–5.5 V supply; requires local 0.1 µF bypass capacitor per TI layout guidelines |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables seamless 24-line decoding without external inverters and 32-line expansion with only one inverter |
| TTL-compatible input thresholds | Eliminates level-shifting requirements when interfacing with legacy 5 V microcontrollers or FPGAs |
| Low propagation delay (≤12 ns) | Minimizes added latency in memory access paths - effective system delay is negligible vs. typical SRAM access time |
| Latch-up immunity >250 mA | Ensures robustness against transient current faults in noisy industrial environments |
| ESD protection (±2000 V HBM) | Reduces risk of handling damage during PCB assembly and field service operations |
Applications
| Memory Address Decoding | Microcontroller Peripheral Selection |
|---|---|
|
Use Scenario: Selecting one of eight SRAM or flash memory banks in a 16-bit embedded system. IC Role / Device Role / Timing Role: Address decoder translating upper address bits into individual chip-enable signals. Use Value: Enables deterministic 12 ns decode latency, preserving tight memory timing budgets without adding wait states. |
Use Scenario: Routing SPI, UART, or GPIO peripherals to a single microcontroller with limited dedicated pins. IC Role / Device Role / Timing Role: Demultiplexer converting 3-bit port output into eight independent peripheral enable lines. Use Value: Reduces MCU pin count requirement by 5 while maintaining full peripheral arbitration capability. |
| Industrial I/O Expansion | Test Equipment Signal Routing |
|
Use Scenario: Controlling eight isolated relay drivers or analog multiplexer channels in a PLC module. IC Role / Device Role / Timing Role: Logic-level translator and gating element for safety-critical enable paths. Use Value: Provides fail-safe HIGH-default outputs (all Yx = HIGH when disabled), preventing unintended actuation during reset. |
Use Scenario: Switching measurement signals between DUT channels and test instrumentation in automated test fixtures. IC Role / Device Role / Timing Role: Low-skew, deterministic path selector ensuring synchronized signal routing. Use Value: Delivers consistent 12 ns channel-switching delay across all eight outputs - critical for time-aligned sampling. |
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 |
|---|---|---|---|
| SN74HCT138PWR | Same pinout and function, but HCT family has wider VCC range (2–6 V) and higher ICC (max 40 mA vs. 4 mA for AHCT) | Better suited for 6 V legacy systems; less optimal for low-power battery-operated designs | Choose SN74HCT138PWR only if 6 V operation or higher noise immunity is required |
| 74LV138PW,118 | Lower VCC range (1.0–5.5 V), 3.5 ns typical tPD, but TTL-incompatible (VIH = 70% VCC) | Requires level-shifting when interfacing with 5 V TTL sources; optimized for 3.3 V/2.5 V domains | Prefer 74LV138PW,118 in modern low-voltage systems where input compatibility is managed externally |
Compared with SN74HCT138PWR and 74LV138PW,118, the SN74AHCT138PWRG4 uniquely balances TTL compatibility, industrial temperature range, and ultra-low quiescent current - making it optimal for mixed-voltage industrial controllers where legacy interface integrity and power efficiency are both critical.
Availability
SN74AHCT138PWRG4 is available at Aetrix Electronics and suitable for industrial control systems, embedded memory subsystems, and test equipment requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for SN74AHCT138PWRG4 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 industrial, automotive, and communications markets.
The SN74AHCT138PWRG4 belongs to TI's advanced high-speed TTL-compatible logic family, engineered specifically for low-latency memory decoding and data-routing applications in harsh industrial environments.
FAQ
What is the maximum operating frequency supported by SN74AHCT138PWRG4?
The SN74AHCT138PWRG4 does not specify a maximum clock frequency, as it is a combinational logic device. Its usable switching rate is determined by propagation delay and load capacitance: with CL = 15 pF, tPLH/tPHL ≤ 12 ns supports reliable operation up to ~40 MHz in worst-case cascaded timing paths. For precise system timing analysis, always reference the SN74AHCT138PWRG4 switching characteristics table under actual VCC and temperature conditions.
Does SN74AHCT138PWRG4 require pull-up or pull-down resistors on unused inputs?
Yes - all unused inputs of the SN74AHCT138PWRG4 must be tied to VCC or GND to prevent floating states that cause excessive ICC, erratic outputs, or increased EMI. TI explicitly mandates this in Section 4.3 of the SN74AHCT138PWRG4 datasheet. Leaving inputs unconnected violates recommended operating conditions and may compromise latch-up immunity and signal integrity.
Is SN74AHCT138PWRG4 pin-compatible with SN74LS138?
No - while both are 3-to-8 decoders, SN74AHCT138PWRG4 uses CMOS technology with TTL-compatible inputs and rail-to-rail outputs, whereas SN74LS138 is bipolar TTL with different DC parameters (e.g., LS138 draws ~30 mA ICC vs. <4 mA for SN74AHCT138PWRG4). Pin numbering matches, but voltage thresholds, drive strength, and power behavior differ significantly; direct substitution requires validation of timing, loading, and noise margins.
Can SN74AHCT138PWRG4 be used as a demultiplexer?
Yes - the SN74AHCT138PWRG4 functions as a 1-to-8 demultiplexer when one enable input (e.g., G1) is used as the data input and A/B/C serve as select lines. In this mode, the selected output mirrors the G1 signal polarity (active-low), enabling serial-to-parallel data distribution - confirmed in Section 6.1 and Table 6-1 of the SN74AHCT138PWRG4 datasheet.
What is the thermal resistance (RθJA) of SN74AHCT138PWRG4 in its TSSOP package?
The SN74AHCT138PWRG4 in TSSOP-16 (PW) package has a junction-to-ambient thermal resistance RθJA of 135.9°C/W, as specified in Section 4.4 of the official datasheet. This value assumes standard JEDEC 2-layer board conditions; actual thermal performance improves with PCB copper area, thermal vias, and airflow - critical for sustained 8 mA output loading across all eight channels.
SN74AHCT138PWRG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- Package/Case:
- 16-TSSOP (0.173", 4.40mm 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:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
SN74AHCT138PWRG4 FAQ
1.How can I place an order for SN74AHCT138PWRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74AHCT138PWRG4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
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The price and inventory of SN74AHCT138PWRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74AHCT138PWRG4 is usually 5 days.
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For technical support, including SN74AHCT138PWRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHCT138PWRG4 requirements.
6.How does Aetrix verify that SN74AHCT138PWRG4 is sourced from the original manufacturer or authorized distributors?
All SN74AHCT138PWRG4 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 SN74AHCT138PWRG4 meets industry standards.
7.What is the process for return or replacement of SN74AHCT138PWRG4?
All SN74AHCT138PWRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHCT138PWRG4, 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 SN74AHCT138PWRG4 part is unused and in its original packaging.
Return procedure for SN74AHCT138PWRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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