SN74ALS253 - Dual 4:1 Mux 3-State ALS TTL | Texas Instruments
MPN: SN74ALS253 β End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $2.5 | $2.50 |
| 10 | $2.25 | $22.50 |
| 100 | $1.9 | $190.00 |
| 500 | $1.6 | $800.00 |
| 1,000 | $1.35 | $1,350.00 |
Drop-in alternatives for SN74ALS253 β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
SN74AS253A
β Drop-Inπ Reference alternative (not in catalog)
SN74LS253
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
SN74F253
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
SN54ALS253
β Drop-Inπ Reference alternative (not in catalog)
SN74HC253
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
CD74HC253
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
74F253
β Drop-In β οΈ εζ°εΎ ιͺθ―π Reference alternative (not in catalog)
SN74ALS253 Maximum Ratings & Electrical Characteristics
| Function | Dual 1-of-4 Data Selector/Multiplexer with 3-State Outputs |
| Technology Family | ALS (Advanced Low-Power Schottky TTL) |
| Channels | 2 x 4:1 |
| Supply Voltage | 5 V (nominal) |
| Output Type | 3-State |
| Output Control | Separate active-low OE per section |
| Select Inputs | 2 (common A, B) |
| Features | 3-state version of ALS153 / SN74AS153 |
| Operating Temperature | 0C to 70C (SN74 series) |
| Package Options | PDIP-16 (N), SOIC-16 (D), CERPACK (FK), CDIP (J) |
| Mounting Type | Through Hole (N) / Surface Mount (D) |
| Pin Count | 16 |
| Applications | Multiplexing from n lines to one line; parallel-to-serial conversion |
| Military Version | SN54ALS253 (J ceramic package) |
SN74ALS253 Pin Configuration
| Pin 1 | OE1 β Output control 1 (active-low, 3-state enable) |
| Pin 2 | B β Select input B (common, MSB) |
| Pin 3 | 1C0 β Data input 1C0 |
| Pin 4 | 1C1 β Data input 1C1 |
| Pin 5 | 1C2 β Data input 1C2 |
| Pin 6 | 1C3 β Data input 1C3 |
| Pin 7 | 1Y β 3-state output 1Y |
| Pin 8 | GND β Ground |
| Pin 9 | 2Y β 3-state output 2Y |
| Pin 10 | 2C0 β Data input 2C0 |
| Pin 11 | 2C1 β Data input 2C1 |
| Pin 12 | 2C2 β Data input 2C2 |
| Pin 13 | 2C3 β Data input 2C3 |
| Pin 14 | A β Select input A (common, LSB) |
| Pin 15 | OE2 β Output control 2 (active-low, 3-state enable) |
| Pin 16 | VCC β Supply voltage (5 V nominal) |
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this digital IC. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
SN74ALS253 is suitable for 6 applications: Bus-Organized System Data Selection, Parallel-to-Serial Data Conversion, Legacy TTL System Maintenance and Repair, Multiplexing n Lines to One Line, Data-Acquisition Front-End Channel Selection, Address and Control-Word Selection in Industrial Controllers.
Bus-Organized System Data Selection
The SN74ALS253 is purpose-built for bus-organized systems where its 3-state outputs interface with and drive shared data lines, per the TI datasheet. Each section's independent active-low OE allows both mux halves to time-share one bus line: one drives while the other floats in high impedance. The ALS drive capability maintains solid logic levels across typical TTL bus loading, and the fast ALS propagation keeps bus turnaround glitches short. Decoupling and controlled bus capacitance (kept within TTL derating limits) are the main performance considerations.
Recommended
Parallel-to-Serial Data Conversion
The datasheet explicitly cites parallel-to-serial conversion as a primary application: stepping the common select inputs A and B through binary sequence 00, 01, 10, 11 serializes one 4-bit word per mux. The ALS family speed ensures each channel settles well within typical counter-clock periods, while the 3-state output gates the data stream onto a shared line. Using a 2-bit binary counter (e.g., 74HC163 family) to drive the select lines yields a clean, glitch-minimized serial data stream for telemetry or legacy serial links.
Recommended
Legacy TTL System Maintenance and Repair
Repairing 1980s-1990s industrial controllers, test equipment, and minicomputer boards often requires exact ALS-family devices to preserve timing margins designed around ALS propagation delay and supply current. The SN74ALS253 drops onto original 16-pin DIP footprints with no PCB rework. Where ALS stock is exhausted, LS or AS variants in the same pinout keep systems running, though timing verification against the original design's worst-case paths is recommended when substituting across TTL subfamilies.
Recommended
Multiplexing n Lines to One Line
The datasheet notes the SN74ALS253 permits multiplexing from n lines to one line by cascading multiple devices whose 3-state outputs share a common line, with each device enabled in turn via its OE control. Two devices give 8-to-1 selection, four give 16-to-1, and so on. ALS propagation delay of each level remains short, so enable decode adds minimal latency. This topology is common in legacy data-acquisition front ends routing multiple sensor channels to a single ADC input stage.
Recommended
Data-Acquisition Front-End Channel Selection
In legacy instrumentation, the SN74ALS253 selects among up to eight analog-conditioned logic-level channels feeding comparators or digital sampling stages, with the 3-state output isolating inactive sections from the shared sense line. Its separate OE per half enables redundant-channel architectures where a backup mux takes over seamlessly. Because it is a digital mux, signals must be logic-level; for true analog switching, an analog multiplexer such as the CD4052 or MPC506 is the appropriate companion or substitute.
Recommended
Address and Control-Word Selection in Industrial Controllers
Industrial PLC I/O boards of the ALS era used dual 4:1 muxes to choose between local and remote address or control-word sources, selected by a mode line driving the OE inputs. The SN74ALS253's independent output controls make source-switchover glitch-manageable, and its TTL thresholds interface directly with bipolar-era controller logic. The ALS low supply current relative to LS reduced backplane power budgets. Modern retrofits should confirm 5V availability and consider HC253 substitutes if timing margins permit.
Recommended
Recommended Products Summary
Engineering reference data for SN74ALS253 β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SN74AS253A | SN74LS253 | SN74HC253 | CD74HC253 |
|---|---|---|---|---|---|
| Package | PDIP-16 (N) / SOIC-16 (D) | PDIP-16 (N) / SOIC-16 (D) - same | PDIP-16 (N) - same | PDIP-16 (N) / SOIC-16 (D) - same | PDIP-16 (N) / SOIC-16 (D) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Renesas Electronics |
| Technology Family | ALS TTL | AS TTL | LS TTL | HC CMOS | HC CMOS |
| Function | Dual 4:1 mux, 3-state outputs | Dual 4:1 mux, 3-state outputs | Dual 4:1 mux, 3-state outputs | Dual 4:1 mux, 3-state outputs | Dual 4:1 mux, 3-state outputs |
| Supply Voltage (nominal) | 5 V | 5 V | 5 V | 2 V to 6 V | 2 V to 6 V |
| Relative Speed | Fast (ALS) | Fastest (AS) | Slower (LS) | [DATA_NEEDED] | [DATA_NEEDED] |
| Relative Supply Current | Low-moderate (ALS) | High (AS) | Moderate (LS) | Very low (CMOS) | Very low (CMOS) |
| Lifecycle Status | Obsolete | Obsolete/EOL | Obsolete/EOL | Active | Active |
Key Differentiators
- ALS speed-power advantage (vs SN74LS253)
- Independent 3-state control per section (vs SN74LS153)
- Exact legacy timing fidelity (vs SN74HC253)
Design Notes
Power the SN74ALS253 from a regulated 5V supply (TTL 4.75V-5.25V recommended range per ALS family conventions). Place a 0.1uF ceramic decoupling capacitor within a few millimeters of the VCC pin; bipolar TTL draws transient current spikes on output transitions, so also include bulk 10uF local capacitance for boards with multiple ALS devices. CMOS substitutes (74HC253) tolerate 2V-6V but check threshold compatibility with surrounding TTL logic before changing families.
When a 3-state output is disabled (OE high), the shared bus line floats and can oscillate or pick up noise. Add a pull-up or pull-down resistor (e.g., 4.7k to 10k) on bus lines that may be undriven, or use bus-hold logic if available. Keep bus stubs short; ALS transition times are fast enough that long unterminated bus runs exhibit reflections visible as glitches at receiver inputs.
Do not confuse the OE polarity: both output controls are active-LOW (outputs enabled when OE = L). Driving OE from a reset controller that asserts high will leave both mux outputs disabled at power-up. Also, select inputs A and B are common to both sections; per-section selection is not possible. When substituting CMOS HC253 for ALS in repairs, verify propagation delay against the original system's setup/hold budget before committing.
Compliance Information
Obsolete bipolar TTL part predating modern compliance documentation; ceramic (J/FK) package options historically contained lead. Verify with TI product page or broker for specific date codes.
