SN74ALS138ADRE4 Texas Instruments Integrated Circuit (Small Outline Packages) In Stock
The SN74ALS138A is a high-performance Schottky-clamped 3-to-8 line decoder/demultiplexer from the ALS logic family, housed in a 16-pin SOIC package. It features 2 active-low and 1 active-high enable inputs and a 50 pF load capacitance specification for fast switching. Used for memory address decoding, peripheral chip-select generation, and bus demultiplexing in embedded systems.
- Manufacturer
- Texas Instruments
- Package
- Small Outline Packages
- Pin Count
- 16
- Lifecycle
- OBSOLETE
- Datasheet
- SN74ALS138ADRE4 Datasheet PDF
- Category
- Integrated Circuit
- Temp Range
- ?°C to 70.0°C
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
What are the key features of SN74ALS138ADRE4?
- 3-to-8 line decoder with Schottky-clamped ALS technology for high-speed performance
- 2 active-low and 1 active-high enable inputs for flexible chip-select control
- 50 pF load capacitance rating supporting high fan-out bus applications
- 8 mA output sink current capability for driving multiple TTL and CMOS loads
- 16-pin SOIC package compatible with standard PCB assembly processes
What is SN74ALS138ADRE4 used for?
The SN74ALS138A is widely used in microprocessor-based systems for decoding 3 address lines into 8 unique chip-select signals, enabling bank-switched memory and peripheral expansion without additional glue logic. Its ALS Schottky construction provides propagation delays suitable for 5 V bus systems running above 10 MHz clock rates. The device also serves as an 8-output demultiplexer in data routing circuits and LED driver selector stages.
What are the specifications of SN74ALS138ADRE4?
| YTEOL | 0 |
| Additional Feature | 2 ACTIVE-LOW AND 1 ACTIVE-HIGH ENABLE INPUT, SCHOTTKY-CLAMPED FOR HIGH PERFORMANCE |
| Family | ALS |
| Input Conditioning | STANDARD |
| JESD-30 Code | R-PDSO-G16 |
| JESD-609 Code | e4 |
| Load Capacitance (CL) | 50pF |
| Logic IC Type | 3-LINE TO 8-LINE DECODER |
| Max I(ol) | 0.008A |
| Number of Functions | 1 |
| Output Polarity | INVERTED |
| Package Body Material | PLASTIC/EPOXY |
| Package Equivalence Code | SOP16,.25 |
| Package Shape | RECTANGULAR |
| Package Style | SMALL OUTLINE |
| Packing Method | TR |
| Peak Reflow Temperature (Cel) | 260 |
| Power Supply Current-Max (ICC) | 10mA |
| Prop. Delay@Nom-Sup | 22ns |
| Propagation Delay (tpd) | 22ns |
| Qualification Status | Not Qualified |
| Supply Voltage-Max (Vsup) | 5.5V |
| Supply Voltage-Min (Vsup) | 4.5V |
| Supply Voltage-Nom (Vsup) | 5V |
| Surface Mount | YES |
| Technology | TTL |
| Temperature Grade | COMMERCIAL |
| Terminal Finish | Nickel/Palladium/Gold (Ni/Pd/Au) |
| Terminal Form | GULL WING |
| Terminal Pitch | 1.27mm |
| Terminal Position | DUAL |
| Time@Peak Reflow Temperature-Max (s) | 30 |
| Package | Small Outline Packages |
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
| Moisture Sensitivity Level | MSL 1 |
| ECCN | EAR99 |
| HTS Code | 8542.39.00.60 |
Where can I find the SN74ALS138ADRE4 datasheet?
SN74ALS138ADRE4 Datasheet DownloadOfficial datasheet from Texas Instruments
What are equivalent replacements for SN74ALS138ADRE4?
Compatible alternatives and drop-in replacements for SN74ALS138ADRE4:
Frequently Asked Questions
How does the SN74ALS138ADRE4 decode a 3-bit address bus into 8 chip-select lines, and how many outputs are active at one time?
The SN74ALS138A takes a 3-bit binary address on its A, B, C inputs and asserts exactly 1 of its 8 active-low outputs at a time, selecting the corresponding memory or peripheral device. The remaining 7 outputs stay high, providing non-overlapping chip selects for up to 8 devices on a single address decode stage.
What output sink current does the SN74ALS138ADRE4 support, and how does the ALS Schottky process improve its switching speed versus standard TTL?
The device sinks up to 8 mA per output with a 50 pF load capacitance, meeting standard TTL drive requirements. The ALS Schottky process reduces propagation delay to typically 5 ns to 11 ns, roughly 2× to 3× faster than standard 74LS-series decoders, enabling use in 8 MHz to 16 MHz bus systems without wait states.
For a 5 V embedded system needing memory bank switching across 8 devices, why is the SN74ALS138ADRE4 suitable compared to CMOS-only decoder alternatives?
The SN74ALS138A is specifically optimized for 5 V TTL-level systems with guaranteed IOL of 8 mA, matching the drive requirements of bipolar memory chips and legacy peripherals. CMOS alternatives like the 74HC138 have lower output drive at 5 V under heavy loads, while the ALS version maintains consistent timing with loads up to 50 pF across the full 0 °C to 70 °C commercial temperature range.
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About Texas Instruments
Texas Instruments (TI) is a global semiconductor company headquartered in Dallas, Texas. TI designs and manufactures analog and embedded processing chips used in industrial, automotive, consumer, communications, and enterprise systems.
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