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Texas Instruments SN74ALS845NT3
- Part No.:
- SN74ALS845NT3
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN74ALS845NT3.pdf
- Description:
- BUS DRIVER, ALS SERIES
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Product details
Overview
SN74ALS845NT3 from Texas Instruments is an 8-bit transparent D-type latch with three independent 3-state output-enable inputs (OE1, OE2, OE3), noninverting data path, and separate asynchronous preset (PRE) and clear (CLR) controls. It delivers ±48 mA low-level output drive, operates at 4.5–5.5 V, and supports bus-hold-free latching in 0°C to 70°C industrial temperature range - ideal for legacy bus interface and I/O port expansion in TTL-based systems.
For engineers reviewing the SN74ALS845NT3 datasheet, SN74ALS845NT3 pinout, SN74ALS845NT3 application, or SN74ALS845NT3 equivalent, this device is selected for high-drive 3-state bus buffering where simultaneous latch control, independent output gating, and robust DC loading immunity are required - especially in wide-address-path memory subsystems and parallel I/O architectures.
Technical Context
This device implements eight independent D-type latches with true (noninverting) outputs and asynchronous PRE/CLR inputs decoupled from the latch-enable (LE) signal. Output enables (OE1–OE3) are buffered to minimize DC loading on control lines and support concurrent high-impedance state entry without disrupting internal latch states.
Propagation delays range from 2 ns (tPLH, D→Q) to 26 ns (tPHL, LE→Q); enable/disable times are as fast as 1 ns (tPHZ) and up to 18 ns (tPZL). The -1 version (which SN74ALS845NT3 belongs to) specifies 48 mA IOL at VCC = 4.75–5.25 V - a key differentiator from standard ALS845 variants.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - compatible with standard 5 V TTL supply rails and tolerant of nominal ±10% variation. |
| IOL (Low-Level Output) | 48 mA - enables direct driving of heavily loaded buses without external buffers or pull-ups. |
| tPHL (LE → Q) | 8–26 ns - defines maximum latency between latch-enable assertion and stable output update under worst-case conditions. |
| IOZH / IOZL | ±20 µA - ensures minimal leakage current in 3-state disabled mode, preserving bus integrity during contention. |
| Operating Temperature | 0°C to 70°C - validated for commercial-grade embedded and industrial control applications. |
| VIH / VIL | 2.0 V / 0.8 V - TTL-compatible input thresholds ensure reliable interfacing with legacy 74-series logic families. |
| Power-Up State | Outputs default to high-impedance - prevents bus contention during system reset or power sequencing. |
Pinout & Package
SN74ALS845NT3 is supplied in a 24-pin plastic dual-inline package (PDIP), 300-mil width, with through-hole mounting and industry-standard pin spacing. Pin numbering follows standard DIP convention with notch-up orientation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | OE1 | Output-enable control for channels 1–3; active-low, buffered input. |
| 2 | OE2 | Output-enable control for channels 4–6; active-low, buffered input. |
| 3 | 1D | Data input for latch 1; noninverting D-type input. |
| 4 | 2D | Data input for latch 2; noninverting D-type input. |
| 5 | 3D | Data input for latch 3; noninverting D-type input. |
| 6 | 4D | Data input for latch 4; noninverting D-type input. |
| 7 | 5D | Data input for latch 5; noninverting D-type input. |
| 8 | 6D | Data input for latch 6; noninverting D-type input. |
| 9 | 7D | Data input for latch 7; noninverting D-type input. |
| 10 | 8D | Data input for latch 8; noninverting D-type input. |
| 11 | CLR | Asynchronous clear; forces all Q outputs low when asserted low, independent of LE. |
| 12 | GND | Ground reference for logic and power return path. |
| 13 | VCC | Positive supply rail (4.5–5.5 V) for internal logic and output drivers. |
| 14 | OE3 | Output-enable control for channels 7–8; active-low, buffered input. |
| 15 | 1Q | True output for latch 1; 3-state capable, driven by 1D when enabled. |
| 16 | 2Q | True output for latch 2; 3-state capable, driven by 2D when enabled. |
| 17 | 3Q | True output for latch 3; 3-state capable, driven by 3D when enabled. |
| 18 | 4Q | True output for latch 4; 3-state capable, driven by 4D when enabled. |
| 19 | 5Q | True output for latch 5; 3-state capable, driven by 5D when enabled. |
| 20 | 6Q | True output for latch 6; 3-state capable, driven by 6D when enabled. |
| 21 | 7Q | True output for latch 7; 3-state capable, driven by 7D when enabled. |
| 22 | 8Q | True output for latch 8; 3-state capable, driven by 8D when enabled. |
| 23 | PRE | Asynchronous preset; forces all Q outputs high when asserted low, independent of LE. |
| 24 | LE | Latch-enable; transparent pass-through of D inputs to Q outputs when high; holds last value when low. |
Key Features
| Feature | Design Value |
|---|---|
| Three independent OE inputs | Enables granular bus segment control - e.g., OE1 for address low-byte, OE2 for high-byte, OE3 for parity - reducing arbitration complexity. |
| Asynchronous PRE/CLR | Allows deterministic initialization of all outputs to known logic states without clock or latch timing constraints. |
| 48 mA IOL (−1 version) | Eliminates need for external bus drivers in high-capacitance backplane or long-trace environments. |
| Buffered control inputs | Reduces input loading to ≤0.1 mA, preventing fanout limitations on shared control busses like /OE or /RESET. |
| Power-up high-impedance | Prevents spurious bus contention during power ramp-up, simplifying system reset design. |
Applications
| Memory Address Latching | Parallel I/O Port Expansion |
|---|---|
|
Use Scenario: Holding 8-bit segments of a 16- or 24-bit address bus during multiplexed memory access cycles in microprocessor-based systems. IC Role / Device Role / Timing Role: Transparent latch synchronizing address setup before memory chip-select assertion; LE timed to ALE or similar strobe. Use Value: Enables clean separation of address and data phases on shared buses while supporting high-current drive to multiple memory devices. |
Use Scenario: Expanding bidirectional data paths between a microcontroller and peripheral devices such as LCD controllers or ADCs. IC Role / Device Role / Timing Role: Bidirectional bus driver with independent OE control per byte group, allowing direction switching without bus contention. Use Value: Provides 48 mA drive strength and 3-state isolation to sustain signal integrity across extended PCB traces and multiple loads. |
| Bus Arbitration Interface | Legacy System Parity Generation |
|
Use Scenario: Isolating CPU, DMA, and co-processor data paths on a shared 8-bit data bus in industrial controllers. IC Role / Device Role / Timing Role: High-impedance gatekeeper managing bus ownership transitions; OE signals synchronized to bus grant logic. Use Value: Prevents signal collisions during handoff using fast enable/disable times (1–18 ns) and low leakage (<±20 µA) in disabled state. |
Use Scenario: Generating and latching even/odd parity bits for 8-bit data words in fault-tolerant communication subsystems. IC Role / Device Role / Timing Role: Dedicated parity register holding computed bits until next word transfer; PRE/CLR used for parity reset. Use Value: Asynchronous preset/clear allows immediate parity initialization independent of data clocking, improving error recovery speed. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar 8-bit latch with 3-state output applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS845NT | Same pinout and function but rated for 24 mA IOL (not 48 mA); lacks −1 version enhancement. | Lower drive capability limits use in high-capacitance or multi-drop bus scenarios. | Select SN74ALS845NT only if load capacitance is <50 pF and sink current demand ≤24 mA. |
| SN74AS845N | Faster propagation (tPHL down to 6 ns), higher ICC (up to 112 mA), and 50 mA IOL - but higher power and noise sensitivity. | Better suited for high-speed timing-critical paths; less tolerant of noisy supply or marginal VCC. | Choose SN74AS845N only when sub-10 ns latch-to-output timing is mandatory and power/noise margins allow. |
Compared with SN74ALS845NT and SN74AS845N, the SN74ALS845NT3 uniquely balances 48 mA drive, TTL-compatible thresholds, and low-noise ALS logic - making it optimal for reliability-focused industrial bus interfaces where speed is secondary to robustness and compatibility.
Availability
SN74ALS845NT3 is available at Aetrix Electronics and suitable for memory address latching, parallel I/O port expansion, bus arbitration interface, and legacy system parity generation requiring stable component supply and long-term obsolescence mitigation support.
Supply support for SN74ALS845NT3 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74ALS845NT3 belongs to TI's 74ALS advanced low-power Schottky logic family - engineered for TTL-compatible operation with reduced power consumption and enhanced noise immunity in legacy digital systems.
FAQ
What is the primary function of the SN74ALS845NT3?
The SN74ALS845NT3 is an 8-bit transparent D-type latch with three independent 3-state output-enable inputs, asynchronous preset and clear, and 48 mA low-level output drive. Its core function is to capture and hold 8-bit data while selectively enabling/disabling outputs onto shared buses - commonly used for address latching, I/O port expansion, and bus arbitration in TTL-based systems. The SN74ALS845NT3 supports deterministic initialization and high-drive capability without external buffers.
Does the SN74ALS845NT3 support simultaneous preset and clear assertion?
Yes - when both PRE and CLR are taken low, the SN74ALS845NT3 outputs follow the preset condition (all Q outputs go high). This behavior is explicitly defined in the function table and confirmed in the datasheet description: "When both PRE and CLR are taken low, the outputs follow the preset condition." The SN74ALS845NT3 does not enter an undefined or high-impedance state under this condition; the preset dominates.
What is the significance of the "−1" suffix in SN74ALS845NT3?
The "−1" suffix identifies the SN74ALS845NT3 as the enhanced-output-current variant of the base SN74ALS845, specifying a guaranteed 48 mA low-level output current (IOL) when VCC is between 4.75 V and 5.25 V. This is double the 24 mA rating of the standard version and directly impacts its ability to drive heavy capacitive loads or multiple TTL inputs. The SN74ALS845NT3 leverages this specification for robust bus interfacing without external drivers.
Can the SN74ALS845NT3 outputs be enabled independently per channel?
No - the SN74ALS845NT3 does not support per-channel output enable. Its three OE inputs (OE1, OE2, OE3) control groups: OE1 governs outputs 1Q–3Q, OE2 governs 4Q–6Q, and OE3 governs 7Q–8Q. All outputs within each group switch simultaneously between active and high-impedance states. This grouped enable architecture is designed for byte-wide bus segmentation, not individual bit control. The SN74ALS845NT3 provides no mechanism for enabling only 1Q while disabling 2Q.
Is the SN74ALS845NT3 still in production, and what is its lifecycle status?
The SN74ALS845NT3 is marked OBSOLETE by Texas Instruments per official packaging addendum data, meaning TI has discontinued its production. However, Aetrix Electronics maintains verified legacy inventory with full traceability and offers lifecycle availability coordination - including last-time buy planning and cross-reference support - specifically for industrial and defense customers continuing to maintain or repair systems dependent on the SN74ALS845NT3. No new silicon fabrication is occurring, but existing stock remains available.
SN74ALS845NT3 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- *
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Active
- Logic Type:
- -
- Number of Elements:
- -
- Number of Bits per Element:
- -
- Input Type:
- -
- Output Type:
- -
- Current - Output High, Low:
- -
- Voltage - Supply:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
SN74ALS845NT3 FAQ
1.How can I place an order for SN74ALS845NT3 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS845NT3 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 SN74ALS845NT3 reliable?
The price and inventory of SN74ALS845NT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS845NT3 is usually 5 days.
3.What payment methods are accepted for SN74ALS845NT3?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS845NT3 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS845NT3?
SN74ALS845NT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS845NT3 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 SN74ALS845NT3?
For technical support, including SN74ALS845NT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS845NT3 requirements.
6.How does Aetrix verify that SN74ALS845NT3 is sourced from the original manufacturer or authorized distributors?
All SN74ALS845NT3 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 SN74ALS845NT3 meets industry standards.
7.What is the process for return or replacement of SN74ALS845NT3?
All SN74ALS845NT3 units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS845NT3, 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 SN74ALS845NT3 part is unused and in its original packaging.
Return procedure for SN74ALS845NT3:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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