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Texas Instruments SN74AHCT138DGVR
- Part No.:
- SN74AHCT138DGVR
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TFSOP (0.173", 4.40mm Width)
- Datasheet:
-
SN74AHCT138DGVR.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16TVSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,000
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Product details
Overview
SN74AHCT138DGVR from Texas Instruments is a 3-line to 8-line decoder/demultiplexer in TVSOP-16 package, designed for high-speed memory decoding and data-routing applications. It features TTL-voltage-compatible inputs, three enable inputs (G1 active-high, G2A/G2B active-low), 7.6 ns typical propagation delay at 5 V/15 pF, ±8 mA output drive, and operates from −40°C to +85°C. It enables compact address decoding in microcontroller-based memory expansion systems.
For engineers reviewing the SN74AHCT138DGVR datasheet, SN74AHCT138DGVR pinout, SN74AHCT138DGVR application, or SN74AHCT138DGVR equivalent, this page delivers verified functional modes, switching characteristics, thermal metrics, and real-world implementation guidance - all specific to the DGV (TVSOP) variant with 3.6 mm × 6.4 mm body size and 16-pin layout.
Technical Context
The SN74AHCT138DGVR implements positive-logic 3-to-8 decoding with three independent enable controls: one active-high (G1) and two active-low (G2A, G2B), allowing flexible 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 the 3-bit binary input (CBA) matches the corresponding line.
Designed for minimal system decoding latency, it achieves sub-12 ns max propagation delay (tPLH/tPHL) under 5 V supply and 15 pF load, with latch-up immunity >250 mA per JESD17 and ESD robustness per JESD22 (±2000 V HBM, ±1000 V CDM). The device uses standard CMOS process with TTL-input thresholds, ensuring compatibility with legacy logic families.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 1.5 V to 5.5 V - supports mixed-voltage system interfacing and 3.3 V/5 V logic domains |
| Propagation Delay | 7.6 ns typical (A/B/C → Y, VCC = 5 V, CL = 15 pF) - enables tight timing budgets in high-speed memory access paths |
| Output Drive | ±8 mA (IOH/IOL) - sufficient to directly drive multiple CMOS/TTL inputs without buffering |
| Input Compatibility | TTL-voltage thresholds (VIH = 2 V, VIL = 0.8 V) - ensures reliable recognition of standard 5 V TTL signal levels |
| Operating Temperature | −40°C to +85°C - qualified for industrial-grade embedded control and instrumentation environments |
| Power Dissipation Cap | 14 pF typical Cpd - low dynamic power consumption supports battery-sensitive or thermally constrained PCB layouts |
| Junction-to-Ambient RθJA | 135.9 °C/W (TVSOP-16) - defines thermal derating limits for continuous operation at ambient up to 85°C |
Pinout & Package
SN74AHCT138DGVR uses a 16-pin Thin Very Small Outline Package (TVSOP) with 0.65 mm lead pitch, 3.6 mm × 6.4 mm body size, and exposed thermal pad (non-electrical). Pin 1 is marked by a beveled corner; leads are gull-wing, RoHS-compliant NIPDAU finish, MSL Level-1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A (1) | Binary select input A | LSB of 3-bit address; must be driven to VCC or GND - floating inputs cause undefined output states |
| B (2) | Binary select input B | Mid-bit of address; used with A and C to determine active output line (Y0–Y7) |
| C (3) | Binary select input C | MSB of address; combined with A/B, selects one of eight decoded outputs |
| G2A (4) | Strobe input 2A | Active-low enable; all outputs forced HIGH when asserted - simplifies hierarchical decoding trees |
| G2B (5) | Strobe input 2B | Second active-low enable; dual strobes reduce need for external gate logic in multi-chip select schemes |
| G1 (6) | Strobe input | Active-high enable; used as primary chip-select or data input in demultiplexing mode |
| Y7 (7) | Output 7 | Active-low decoded output; asserted only when G1=HIGH, G2A=G2B=LOW, and CBA=111 |
| GND (8) | Ground reference | Primary return path for logic and output currents; requires low-impedance PCB connection |
| Y6 (9) | Output 6 | Active-low output for CBA=110; shares same enable conditions as Y7 but distinct decode path |
| Y5 (10) | Output 5 | Active-low output for CBA=101; electrically isolated from other outputs during normal operation |
| Y4 (11) | Output 4 | Active-low output for CBA=100; supports independent peripheral selection in address-mapped I/O |
| Y3 (12) | Output 3 | Active-low output for CBA=011; usable as chip-enable for memory banks or peripheral controllers |
| Y2 (13) | Output 2 | Active-low output for CBA=010; provides deterministic timing with <12 ns max delay variation across temperature |
| Y1 (14) | Output 1 | Active-low output for CBA=001; compatible with 74-series logic fan-out requirements |
| Y0 (15) | Output 0 | Active-low output for CBA=000; lowest-address line - commonly used for boot ROM or primary peripheral |
| VCC (16) | Positive supply | Must be bypassed with 0.1 µF ceramic capacitor placed ≤2 mm from pin - critical for noise immunity and switching stability |
Key Features
| Feature | Design Value |
|---|---|
| Three enable inputs (G1, G2A, G2B) | Enables 24-line decoding without external inverters and 32-line decoding with only one inverter - reduces component count and board area |
| TTL-voltage compatible inputs | Accepts standard 5 V TTL logic levels (VIH ≥ 2 V, VIL ≤ 0.8 V) while operating from 3.3 V supply - bridges legacy and modern logic families |
| Latch-up immunity >250 mA | Meets JESD17 Class II requirements - prevents destructive parasitic SCR activation during transient overvoltage events |
| ESD protection (HBM ±2000 V, CDM ±1000 V) | Exceeds JEDEC JESD22 standards - ensures robust handling during assembly and field operation without special ESD controls |
| Low dynamic power (Cpd = 14 pF) | Minimizes switching current and heat generation in high-frequency address decoding - supports dense PCB layouts |
Applications
| Memory Address Decoding | Peripheral Device Selection |
|---|---|
Use Scenario: Expanding 16-bit microcontroller address bus to select among eight 32 KB memory blocks in an embedded data logger. IC Role / Device Role / Timing Role: 3-to-8 decoder mapping upper address bits (A15–A13) to individual chip-enable lines for SRAM and Flash ICs. Use Value: Eliminates discrete gate logic, reduces propagation delay to <12 ns, and maintains deterministic timing across −40°C to +85°C operating range. |
Use Scenario: Selecting between UART, SPI ADC, CAN transceiver, and GPIO expander on a modular industrial controller PCB. IC Role / Device Role / Timing Role: Demultiplexer using G1 as main enable and CBA as peripheral ID - each output drives dedicated /CS line. Use Value: Enables single-cycle peripheral arbitration with no additional glue logic; TTL-compatible inputs interface directly with MCU GPIOs. |
| Bus Multiplexing | Logic State Translation |
Use Scenario: Routing sensor data from eight analog front-ends to a shared ADC channel based on digital command signals. IC Role / Device Role / Timing Role: Active-low demultiplexer where G1 serves as data-valid strobe and CBA selects source channel. Use Value: Provides glitch-free channel switching with <1 ns skew between outputs - critical for synchronized sampling systems. |
Use Scenario: Converting 3-bit parallel control signals from a 5 V FPGA to eight isolated 3.3 V enable lines for LED drivers. IC Role / Device Role / Timing Role: Level-shifting decoder leveraging TTL input thresholds and 3.3 V supply - no external level shifters required. Use Value: Achieves bidirectional voltage domain bridging with guaranteed VIH/VIL margins and <10 ns delay variation over temperature. |
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 |
|---|---|---|---|
| SN74LV138AIPW | Lower supply range (1.65–5.5 V), higher max tPD (16 ns @ 3.3 V), LV-CMOS inputs (not TTL-compatible) | Requires level-shifting for legacy 5 V TTL sources; better suited for 1.8 V/2.5 V systems | Select when operating below 2.5 V or prioritizing ultra-low static current (<1 µA ICC) |
| 74HC138PW | CMOS inputs (VIH = 3.15 V min @ 4.5 V), slower tPD (21 ns typical @ 4.5 V), no TTL threshold guarantee | Not interoperable with 5 V TTL without pull-ups; unsuitable for direct replacement in mixed-signal legacy designs | Choose only if existing design uses HC-family timing margins and all inputs are CMOS-driven |
Compared with SN74LV138AIPW and 74HC138PW, the SN74AHCT138DGVR uniquely combines TTL input compatibility, sub-12 ns speed at 5 V, and industrial temperature range - making it the only drop-in solution for upgrading legacy 74LS138-based memory decoders without layout or firmware changes.
Availability
SN74AHCT138DGVR is available at Aetrix Electronics and suitable for industrial control systems, memory expansion modules, and peripheral interface boards requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.
Supply support for SN74AHCT138DGVR 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 experience in high-reliability industrial and automotive components.
The SN74AHCT138DGVR belongs to TI's AHCT logic family, engineered specifically for high-speed memory decoding and data-routing applications where TTL compatibility, low propagation delay, and industrial temperature operation are essential.
FAQ
What is the maximum clock frequency supported by SN74AHCT138DGVR?
The SN74AHCT138DGVR is not a clocked device - it is a combinational decoder with no internal clock. Its effective operating frequency depends on input transition rate and load capacitance. With 15 pF load and 5 V supply, it supports input edge rates up to 50 MHz (20 ns/V limit) while maintaining specified tPLH/tPHL <12 ns. For reliable operation, keep input rise/fall times ≤10 ns.
Can SN74AHCT138DGVR operate at 3.3 V supply while interfacing with 5 V TTL inputs?
Yes. The SN74AHCT138DGVR is explicitly designed for TTL-voltage compatibility: its VIH threshold is 2.0 V (min) and VIL is 0.8 V (max) across 1.5–5.5 V VCC range. At 3.3 V supply, it correctly interprets standard 5 V TTL logic highs (>2.4 V) and lows (<0.8 V), enabling seamless level translation without external components.
How should unused inputs be handled on SN74AHCT138DGVR?
All unused inputs on SN74AHCT138DGVR - including A, B, C, G2A, G2B, and G1 - must be tied to a defined logic level (VCC or GND) to prevent floating states that cause excessive ICC, output oscillation, or latch-up. TI recommends connecting unused enables to inactive states (e.g., G2A/G2B to VCC, G1 to GND) and unused select lines to GND unless required for expansion.
Is SN74AHCT138DGVR pin-compatible with other 16-pin decoder packages like SOIC or SSOP?
No. While SN74AHCT138DGVR shares identical logic functionality and pin numbering with SOIC (D), SSOP (DB), and TSSOP (PW) variants, its TVSOP (DGV) package has different mechanical dimensions (3.6 mm × 6.4 mm body, 0.65 mm pitch) and footprint - requiring unique PCB land patterns. Direct physical replacement is not possible without board redesign.
What thermal considerations apply to SN74AHCT138DGVR in continuous operation?
With RθJA = 135.9 °C/W (TVSOP), SN74AHCT138DGVR's junction temperature rises significantly under load. At 85°C ambient and 25 mA total output current, power dissipation reaches ~12 mW - resulting in ~1.6°C junction rise. For sustained operation near max ratings, ensure adequate copper pour under the thermal pad and avoid stacking heat-generating components nearby.
SN74AHCT138DGVR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74AHCT
- Package/Case:
- 16-TFSOP (0.173", 4.40mm 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:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TVSOP
SN74AHCT138DGVR FAQ
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For technical support, including SN74AHCT138DGVR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74AHCT138DGVR requirements.
6.How does Aetrix verify that SN74AHCT138DGVR is sourced from the original manufacturer or authorized distributors?
All SN74AHCT138DGVR 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 SN74AHCT138DGVR meets industry standards.
7.What is the process for return or replacement of SN74AHCT138DGVR?
All SN74AHCT138DGVR units undergo pre-shipment inspection (PSI). If there is an issue with SN74AHCT138DGVR, 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 SN74AHCT138DGVR part is unused and in its original packaging.
Return procedure for SN74AHCT138DGVR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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