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STMicroelectronics 74VHC138TTR
- Part No.:
- 74VHC138TTR
- Manufacturer:
- STMicroelectronics
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
74VHC138TTR.pdf
- Description:
- IC DECODER/DEMUX 1X3:8 16TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:4,461
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Product details
Overview
74VHC138TTR from STMicroelectronics is a high-speed CMOS 3-to-8 line decoder (inverting) with pin- and function-compatibility to standard 74-series 138 devices. It operates from 2V to 5.5V, delivers 5.7ns typical propagation delay at 5V, supports ±8mA symmetrical output drive, and features power-down input protection enabling 0–7V input tolerance regardless of VCC. It is used in memory address decoding and bus demultiplexing in industrial control and embedded systems.
For engineers reviewing the 74VHC138TTR datasheet, 74VHC138TTR pinout, 74VHC138TTR application, or 74VHC138TTR equivalent, key selection criteria include its 3-enable-input architecture (G1, G2A, G2B), guaranteed noise immunity (28% VCC), latch-up robustness, and TSSOP-16 package suitability for space-constrained PCB layouts.
Technical Context
The 74VHC138TTR implements a fully decoded 3-bit binary input (A, B, C) to eight active-low outputs (Y0–Y7), with three independent enable inputs (G1, G2A, G2B) that must satisfy G1 = HIGH and G2A = G2B = LOW for decoding to occur. Its logic is strictly inverting: only one output goes LOW per valid input combination.
Designed using sub-micron C2MOS technology, it integrates input protection diodes rated for ±20mA DC current, 2kV HBM ESD immunity, and power-down safe inputs that accept voltages up to 7V independent of VCC. Propagation delays are balanced (tPLH ≈ tPHL) and specified across –55°C to +125°C operating range.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 2V to 5.5V - supports mixed-voltage interfacing (e.g., 5V logic driving 3.3V systems) |
| tPD (Typ.) | 5.7ns at VCC = 5V, CL = 15pF - enables high-speed address decoding in ≤20MHz memory systems |
| IOH/IOL | ±8mA min. - drives standard TTL loads and multiple CMOS inputs without buffering |
| VNIH/VNIL | 28% VCC min. - ensures reliable switching under noisy industrial supply conditions |
| ICC (Max.) | 4µA at TA = 25°C - suitable for low-power standby modes in battery-backed systems |
| Input Voltage Range | –0.5V to 7.0V - allows hot-swap and level-shifting operation without external clamping |
| ESD Rating | 2kV HBM - meets IEC 61000-4-2 Level 2 for board-level robustness |
Pinout & Package
TSSOP-16 package: 4.4mm × 5.0mm body, 0.65mm pitch, 1.2mm max height, lead-free and RoHS compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3 (A, B, C) | Binary Address Inputs | Select one of eight outputs; internally terminated with protection diodes to VCC/GND |
| 4 (G2A), 5 (G2B) | Active-Low Enable Inputs | Both must be LOW (with G1 HIGH) to activate decoding; support cascading via OR-logic |
| 6 (G1) | Active-High Enable Input | Primary global enable; overrides G2A/G2B when LOW, forcing all outputs HIGH |
| 7, 9–15 (Y0–Y7) | Inverting Decoder Outputs | Open-drain compatible; each sinks ≥8mA when LOW, high-impedance when HIGH |
| 8 (GND) | Ground Reference | Return path for all internal logic and output currents; decoupling capacitor required |
| 16 (VCC) | Positive Supply | Power rail for internal logic and output drivers; must be bypassed within 5mm of pin |
Key Features
| Feature | Design Value |
|---|---|
| Triple Enable Architecture | G1 (active-HIGH), G2A/G2B (active-LOW) - enables hierarchical address decoding and multi-chip select logic |
| Input Overvoltage Tolerance | 0–7V input range independent of VCC - eliminates level-shifters in mixed-supply systems |
| Balanced Propagation Delays | tPLH ≈ tPHL - prevents pulse distortion in timing-critical enable chains |
| Latch-Up Immunity | Improved C2MOS process - withstands >200mA transient current without destructive latch-up |
| Symmetrical Output Drive | |IOH| = IOL = 8mA min. - ensures consistent rise/fall times into capacitive loads |
Applications
| Memory Address Decoding | Bus Demultiplexing |
|---|---|
Use Scenario: Selecting one of eight memory banks in a microcontroller-based data logger with 512KB SRAM expansion. IC Role / Device Role / Timing Role: Active-low 3-to-8 decoder generating chip-select signals synchronized to address bus transitions. Use Value: Enables deterministic 5.7ns access latency per bank and eliminates external gating logic due to triple-enable cascade capability. | Use Scenario: Routing UART, SPI, and I²C peripherals from a single MCU port to separate sensor modules on a modular industrial gateway. IC Role / Device Role / Timing Role: Bus selector translating 3-bit peripheral ID into dedicated enable lines with simultaneous deactivation of unused paths. Use Value: Reduces signal crosstalk by isolating inactive buses and supports hot-plug detection via G2A/G2B status monitoring. |
| Industrial I/O Expansion | Programmable Logic Interface |
Use Scenario: Controlling 8 isolated relay drivers in a PLC backplane where input voltage may float up to 7V during field wiring faults. IC Role / Device Role / Timing Role: Fault-tolerant decoder accepting direct 24V-derived logic levels via resistive dividers without clamping diodes. Use Value: Eliminates external protection circuitry and maintains decode integrity during brown-out or overvoltage transients. | Use Scenario: Configuring FPGA I/O bank assignments in a reconfigurable test instrument using DIP-switch-encoded address inputs. IC Role / Device Role / Timing Role: Static configuration decoder mapping mechanical switch states to parallel FPGA control bits with glitch-free power-up default (all outputs HIGH). Use Value: Guarantees known reset state via G1-controlled initialization and avoids metastability during FPGA configuration. |
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 |
|---|---|---|---|
| SN74HC138PWR | Same logic function, but TI part uses HC process: higher ICC (80µA max), slower tPD (21ns typ. at 6V), no 7V input tolerance | Not suitable for mixed-voltage or overvoltage-tolerant designs; requires strict 2–6V VCC compliance | Select when cost is primary and system operates strictly within 4.5–5.5V with no field-wiring overvoltage risk |
| 74LVC138PW,118 | NXP LVC variant: 1.65–5.5V VCC, 5.5ns tPD at 3.3V, but only 5.5V absolute max input rating and no power-down protection | Lacks 0–7V input safety margin; unsuitable for industrial environments with cable-induced transients | Prefer for portable 3.3V-only systems where board space and speed outweigh ruggedness requirements |
Compared with SN74HC138PWR and 74LVC138PW,118, the 74VHC138TTR uniquely combines 7V input tolerance, 4µA quiescent current, and 5.7ns speed-making it optimal for industrial designs requiring both low power and field-hardened interfacing.
Availability
74VHC138TTR is available at Aetrix Electronics and suitable for memory address decoding, industrial I/O expansion, and programmable logic interface applications requiring stable component supply across extended temperature ranges and mixed-voltage environments.
Supply support for 74VHC138TTR 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management ICs with vertical manufacturing and broad analog/mixed-signal portfolio.
The 74VHC series targets high-speed, low-power logic applications in industrial control and embedded systems, emphasizing robustness, wide supply range, and compatibility with legacy 74-series architectures.
FAQ
Can the 74VHC138TTR operate reliably at 2.0V supply?
Yes. The device is fully specified down to 2.0V VCC, with guaranteed VIH = 1.5V (min) and VOL = 0.1V (max) at IO = 50µA. Propagation delay increases to 13.0ns (max) at 2V, but logic thresholds and noise margins remain functional across –55°C to +125°C.
What happens if G1 is left floating?
G1 must not be left floating: its internal structure lacks pull-up/pull-down, so undefined voltage may cause partial enable states and excessive ICC. STMicroelectronics recommends tying G1 to VCC via 10kΩ resistor or directly connecting to controlled logic to ensure predictable HIGH/LOW assertion.
Is the 74VHC138TTR pin-compatible with 74LS138 in TSSOP package?
No. While functionally identical and pin-number compatible (16-pin TSSOP), the 74VHC138TTR has different electrical characteristics: LS138 uses bipolar technology, draws ~20mA ICC, lacks 7V input tolerance, and has asymmetric output drive. Direct replacement requires validation of fanout, noise margin, and power delivery.
Does the device support hot insertion in live backplanes?
Yes - the 0–7V input tolerance, power-down protection, and 2kV ESD rating allow safe connection to powered systems. However, VCC must be established before applying input signals, and GND should make first contact per IEC 61000-4-2 hot-swap guidelines to avoid latch-up during insertion.
74VHC138TTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- 74VHC
- 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:
- 2V ~ 5.5V
- Operating Temperature:
- -55°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-TSSOP
74VHC138TTR FAQ
1.How can I place an order for 74VHC138TTR through Aetrix?
Please submit a Request for Quotation (RFQ) for 74VHC138TTR 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 74VHC138TTR reliable?
The price and inventory of 74VHC138TTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74VHC138TTR is usually 5 days.
3.What payment methods are accepted for 74VHC138TTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74VHC138TTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74VHC138TTR?
74VHC138TTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74VHC138TTR 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 74VHC138TTR?
For technical support, including 74VHC138TTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74VHC138TTR requirements.
6.How does Aetrix verify that 74VHC138TTR is sourced from the original manufacturer or authorized distributors?
All 74VHC138TTR 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 74VHC138TTR meets industry standards.
7.What is the process for return or replacement of 74VHC138TTR?
All 74VHC138TTR units undergo pre-shipment inspection (PSI). If there is an issue with 74VHC138TTR, 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 74VHC138TTR part is unused and in its original packaging.
Return procedure for 74VHC138TTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
74VHC138TTR Tags
-
SN74HC138DR
Texas Instruments
-
TC7SB3157CFU,LF(CT
Toshiba Semiconductor and Storage
-
74CBTLV3257PW,118
Nexperia USA Inc.
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SN74CBTLV3257PWR
Texas Instruments
-
74CBTLV3257GUX
Nexperia USA Inc.
-
74HC154BQ,118
Nexperia USA Inc.
-
P3S0200GMX
NXP USA Inc.
-
SN74CB3Q3245PWR
Texas Instruments
-
SN74CB3Q3257RGYR
Texas Instruments
-
TCA9543APWR
Texas Instruments
-
TCA9546APWR
Texas Instruments
-
SN74HC138N
Texas Instruments
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