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Texas Instruments SN74HCT257D
- Part No.:
- SN74HCT257D
- Manufacturer:
- Texas Instruments
- Category:
- Signal Switches, Multiplexers, Decoders
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
SN74HCT257D.pdf
- Description:
- IC MULTIPLEXER 4 X 2:1 16SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:470
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Product details
Overview
SN74HCT257D from Texas Instruments is a quadruple 2-line to 1-line data selector/multiplexer with 3-state outputs, designed for bus-organized digital systems. It operates at 4.5–5.5 V, delivers ±6-mA output drive, exhibits typical propagation delay of 17 ns at 5.5 V, and supports TTL-voltage-compatible inputs - enabling direct interface with legacy 5-V logic buses in industrial control and instrumentation.
For engineers reviewing the SN74HCT257D datasheet, SN74HCT257D pinout, SN74HCT257D application, or SN74HCT257D equivalent, key selection criteria include its 16-pin SOIC package, active-low 3-state enable (G), quad-channel independent select (A/B), and guaranteed high-impedance outputs when OE is high - critical for shared-bus arbitration and signal routing integrity.
Technical Context
The SN74HCT257D implements four independent 2:1 multiplexers sharing a common output-enable (G) input, each selecting between A or B data inputs based on the A/B address line. All outputs enter high-impedance state when G is high, isolating the device from the bus without external pull-ups.
Its HCT logic family ensures CMOS power efficiency with TTL input thresholds (VIH = 2 V, VIL = 0.8 V), enabling seamless interoperability with 74LS and other bipolar logic families while maintaining low ICC (≤80 µA) and fast switching (tpd ≤34 ns at 5.5 V, CL = 50 pF).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - compatible with standard 5-V logic rails and tolerant of supply ripple up to ±0.5 V. |
| Propagation Delay (tpd) | 17 ns typical at 5.5 V, CL = 50 pF - enables reliable operation in 25-MHz bus systems with margin. |
| Output Drive | ±6 mA at 5 V - sufficient to drive 10 LSTTL loads or terminate short PCB traces without buffering. |
| Input Compatibility | TTL-voltage level - accepts 0.8 V/2.0 V thresholds, eliminating need for level shifters when interfacing with 74LS devices. |
| ICC (Max) | 80 µA - ultra-low static current supports low-power standby modes in battery-backed or energy-sensitive systems. |
| 3-State Enable | Active-low G input - asserts high-impedance outputs synchronously across all four channels for clean bus release. |
| Input Leakage | ±1 µA max - minimizes loading on upstream drivers and preserves signal integrity in high-impedance source configurations. |
Pinout & Package
SN74HCT257D uses a 16-pin SOIC (D) package measuring 9.90 mm × 3.90 mm, with standard JEDEC MS-012AC outline and gull-wing leads suitable for reflow soldering.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | A/B | Common address select for all four multiplexers - determines whether A or B input is routed to Y output. |
| 2–4, 5–7, 10–11, 13–14 | 1A/1B/1Y, 2A/2B/2Y, 3A/3B/3Y, 4A/4B/4Y | Four independent 2:1 data paths - each pair routes selected input to dedicated output under A/B control. |
| 8 | GND | Ground reference for logic and power - must be low-impedance connection to minimize noise coupling into outputs. |
| 9–12 | 3Y, 3B, 3A, 4Y | Continuation of channel I/O mapping - pin order follows functional grouping per TI's D-package top-view layout. |
| 15 | G | Global 3-state enable - low = outputs active; high = all Y outputs enter high-Z, decoupling from bus. |
| 16 | VCC | Positive supply - requires local 0.1-µF ceramic bypass capacitor placed adjacent to pin for stable switching performance. |
Key Features
| Feature | Design Value |
|---|---|
| Bus-interface optimized outputs | High-current 3-state drivers (±6 mA) allow direct connection to 5-V system buses without series resistors or buffers. |
| TTL-compatible inputs | VIH = 2.0 V / VIL = 0.8 V thresholds ensure reliable recognition of legacy 74LS/ALS logic levels without translation circuitry. |
| Low static power | ICC ≤ 80 µA max eliminates thermal concerns in dense logic arrays and extends battery life in portable instrumentation. |
| Buffered inputs and outputs | Internal buffering prevents loading effects between channels and improves noise immunity on shared select/address lines. |
| Controlled output transition | Specified tdis/ten (17–34 ns) ensures predictable timing windows for bus arbitration and avoids metastability during enable transitions. |
Applications
| Industrial PLC I/O Expansion | Legacy System Bus Multiplexing |
|---|---|
Use Scenario: Adding discrete sensor inputs to a 5-V backplane bus in programmable logic controllers where space and power are constrained. IC Role / Device Role / Timing Role: SN74HCT257D acts as a channel-select gate, routing analog-to-digital converter outputs or digital sensor streams onto a shared data bus under microcontroller address control. Use Value: Enables 4:1 signal consolidation per IC with deterministic 17-ns latency and zero additional power overhead beyond baseline logic consumption. | Use Scenario: Interfacing multiple 74LS-based peripheral modules (e.g., UARTs, timers) to a single 8-bit microprocessor data bus. IC Role / Device Role / Timing Role: SN74HCT257D serves as a bidirectional bus multiplexer, allowing the CPU to read from or write to one peripheral at a time while isolating others via 3-state control. Use Value: Eliminates need for discrete transceivers or complex glue logic by providing native TTL-compatible I/O and synchronous bus release. |
| Test Equipment Signal Routing | Digital Audio Data Switching |
Use Scenario: Configurable signal path selection in automated test equipment requiring precise routing of stimulus/response signals between DUT and measurement instruments. IC Role / Device Role / Timing Role: SN74HCT257D functions as a digitally controlled analog switch surrogate - routing digital control/data lines with sub-20-ns skew across four parallel paths. Use Value: Provides deterministic, glitch-free switching with no DC bias requirements or charge injection - unlike analog switches - ideal for logic-level test sequencing. | Use Scenario: Selecting between two stereo audio data sources (e.g., SPDIF receiver vs. internal DAC) in consumer audio SoC subsystems operating at 5 V. IC Role / Device Role / Timing Role: SN74HCT257D performs parallel 4-bit data path selection for left/right channel sample words, synchronized to frame clock edges. Use Value: Delivers bit-accurate, low-jitter routing with <1 µA input leakage - preserving signal integrity in multi-source digital audio routing trees. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 2:1 multiplexer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HC257N | Same pinout and function but HC logic family - higher VIH (3.15 V min), lower drive (±4 mA), slower tpd (27 ns typ at 6 V). | Suitable only in pure CMOS systems with ≥3.3-V supplies; not interoperable with TTL-level inputs without level shifting. | Select SN74HC257N only if operating above 2 V and driving lighter loads; avoid in mixed 5-V TTL/CMOS environments. |
| 74ACT257SCX | ACT family - faster tpd (9 ns typ), higher drive (±24 mA), wider VCC range (4.5–5.5 V), but higher ICC (4 mA max). | Better for high-speed bus arbitration but increases system power and EMI; requires stricter layout for signal integrity. | Choose 74ACT257SCX when >20-MHz bus timing margins are required and thermal/power budgets permit. |
Compared with SN74HCT257D, SN74HC257N sacrifices TTL compatibility and speed for lower power, while 74ACT257SCX trades higher ICC and layout sensitivity for superior timing performance - making SN74HCT257D the optimal balance for robust 5-V bus interfacing.
Availability
SN74HCT257D is available at Aetrix Electronics and suitable for industrial PLC I/O expansion, legacy system bus multiplexing, test equipment signal routing, and digital audio data switching requiring stable component supply and long-term obsolescence management.
Supply support for SN74HCT257D 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 50 years of innovation in industrial, automotive, and communications markets.
The SN74HCT257D belongs to TI's 74HCT logic family - engineered specifically to bridge TTL and CMOS domains in 5-V systems, delivering pin-compatible replacements for legacy 74LS logic with CMOS power efficiency and noise immunity.
FAQ
What is the recommended operating voltage range for SN74HCT257D?
The SN74HCT257D is specified for operation from 4.5 V to 5.5 V. Operation outside this range may cause unreliable switching behavior or exceed absolute maximum ratings. The device draws minimal current (≤80 µA) across this range, making it suitable for applications with regulated 5-V rails subject to minor tolerance drift.
How does the output-enable (G) pin function on SN74HCT257D?
The G pin on SN74HCT257D is an active-low 3-state enable controlling all four Y outputs simultaneously. When G is low, outputs reflect the selected A/B input; when G is high, all Y pins enter high-impedance state, electrically disconnecting the device from the bus. This allows safe sharing of data lines among multiple devices without contention.
Can SN74HCT257D interface directly with 74LS logic devices?
Yes, SN74HCT257D features TTL-compatible input thresholds (VIH = 2.0 V, VIL = 0.8 V), enabling direct connection to 74LS outputs without level-shifting circuitry. Its outputs also drive ±6 mA at 5 V - sufficient to sink/source 10 LSTTL unit loads - ensuring robust fanout in mixed-logic systems.
What is the typical propagation delay of SN74HCT257D and under what conditions?
The typical propagation delay (tpd) of SN74HCT257D is 17 ns, measured at VCC = 5.5 V, TA = 25°C, and CL = 50 pF. This value applies to transitions from A/B or G inputs to Y outputs and reflects worst-case path timing used for synchronous bus design margining in 5-V digital systems.
Is SN74HCT257D available in tape-and-reel packaging for automated assembly?
Yes, SN74HCT257D is available in tape-and-reel format as SN74HCT257DR.A - a 16-pin SOIC package supplied in 2500-unit reels compliant with JEDEC standards, RoHS-certified, and rated MSL Level-1 for unlimited floor life at ≤30°C/60% RH. This configuration supports high-volume SMT placement with verified pin-1 quadrant alignment (Q1).
SN74HCT257D Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HCT
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Type:
- Multiplexer
- Circuit:
- 4 x 2:1
- Independent Circuits:
- 1
- Current - Output High, Low:
- 6mA, 6mA
- 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-SOIC
SN74HCT257D FAQ
1.How can I place an order for SN74HCT257D through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HCT257D 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 SN74HCT257D reliable?
The price and inventory of SN74HCT257D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HCT257D is usually 5 days.
3.What payment methods are accepted for SN74HCT257D?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HCT257D transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HCT257D?
SN74HCT257D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HCT257D 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 SN74HCT257D?
For technical support, including SN74HCT257D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HCT257D requirements.
6.How does Aetrix verify that SN74HCT257D is sourced from the original manufacturer or authorized distributors?
All SN74HCT257D 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 SN74HCT257D meets industry standards.
7.What is the process for return or replacement of SN74HCT257D?
All SN74HCT257D units undergo pre-shipment inspection (PSI). If there is an issue with SN74HCT257D, 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 SN74HCT257D part is unused and in its original packaging.
Return procedure for SN74HCT257D:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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