My Inquiry
My Account
Texas Instruments SN74ALS845NT
- Part No.:
- SN74ALS845NT
- Manufacturer:
- Texas Instruments
- Package:
- -
- Datasheet:
-
SN74ALS845NT.pdf
- Description:
- BUS DRIVER, ALS SERIES
- Quantity:
- Payment:
- Shipping:
Inventory:1,187
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS845NT 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 drive (IOL), operates at 4.5–5.5 V, and supports bus-driving applications requiring high-impedance isolation and latched data retention. It is used in legacy industrial control backplanes and parallel I/O expansion interfaces.
For engineers reviewing the SN74ALS845NT datasheet, SN74ALS845NT pinout, SN74ALS845NT application, or SN74ALS845NT equivalent, key selection considerations include its 24-pin PDIP (NT) package, 13 ns max tPLH propagation delay, 48 mA IOL capability (−1 version), bus-structured pinout, and independent PRE/CLR functionality for deterministic output initialization.
Technical Context
The SN74ALS845NT implements eight independent transparent D latches with edge-independent asynchronous control: PRE and CLR override LE and directly force Q outputs high or low regardless of clock or data state. Its triple OE architecture enables granular bus segment control-each OE input gates a subset of outputs without affecting internal latch operation or stored data.
Designed for ALS (Advanced Low-Power Schottky) logic family compatibility, it features buffered control inputs to reduce DC loading on upstream drivers, power-up high-impedance outputs to prevent bus contention at startup, and a bus-optimized pinout that minimizes trace crossovers in dense PCB layouts. All timing parameters are specified over 0°C to 70°C with CL = 50 pF.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation across standard TTL-compatible supply rails with margin for ripple. |
| IOL (max) | 48 mA - Enables direct driving of heavy capacitive buses (e.g., >100 pF) without external buffers. |
| tPLH / tPHL (D→Q) | 2 ns min / 13 ns max - Supports reliable latching at sustained data rates up to ~30 MHz in short-path configurations. |
| tPZH / tPLZ (OE→Q) | 1 ns min / 12 ns max - Allows fast, glitch-free bus turnarounds during multiplexed read/write cycles. |
| VIH / VIL | 2.0 V / 0.8 V - Fully compatible with standard TTL and LS logic voltage thresholds for seamless interfacing. |
| Operating Temp | 0°C to 70°C - Qualified for commercial-grade embedded systems including test equipment and office automation hardware. |
| ICC (outputs disabled) | 25–42 mA - Reflects quiescent current draw when all outputs are tri-stated, critical for power budgeting in idle states. |
Pinout & Package
SN74ALS845NT is supplied in a 24-pin plastic dual in-line package (PDIP), 300-mil width, with through-hole mounting and industry-standard pin spacing (0.1″). The package is leaded, non-RoHS-compliant per TI's 2010 packaging addendum, and marked "NT" per TI nomenclature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | Data inputs (1D–8D) | Noninverting D inputs for each of eight transparent latches; accept standard TTL logic levels. |
| 9, 10, 11, 12, 13, 14, 15, 16 | Output enables (OE1–OE3 unused pins) | OE1, OE2, OE3 are active-low 3-state controls; pins 9–12 map to OE1/OE2/OE3 per datasheet top view. |
| 17, 18, 19, 20, 21, 22, 23, 24 | Outputs (1Q–8Q) | True, 3-state buffered outputs; high-impedance when any associated OE is high. |
| 13 | Latch enable (LE) | Active-high clock input; transparent when high, latches data on falling edge. |
| 11 | Clear (CLR) | Asynchronous active-low reset; forces all Q outputs low independent of LE or data. |
| 1 | Preset (PRE) | Asynchronous active-low set; forces all Q outputs high independent of LE or data. |
| 10 | GND | Ground reference for all logic and output stages. |
| 24 | VCC | Positive supply rail (4.5–5.5 V); powers internal logic and output drivers. |
Key Features
| Feature | Design Value |
|---|---|
| Independent PRE/CLR | Enables deterministic output initialization without relying on LE timing or data setup-critical for system reset sequences. |
| Triple OE architecture | Allows partitioned bus control: e.g., OE1 for address lines, OE2 for data lines, OE3 for control flags-reducing external gating logic. |
| Bus-structured pinout | Groups D inputs (pins 1–8), Q outputs (17–24), and control signals (PRE, CLR, LE, OEs) to minimize PCB routing congestion in backplane designs. |
| Power-up high-Z | Prevents bus contention at power-on before firmware initializes control signals-eliminates need for external pull-ups/downs. |
| Buffered control inputs | Reduces DC loading on upstream drivers by >5× vs. unbuffered TTL inputs, preserving signal integrity in fan-out-heavy systems. |
Applications
| Parallel I/O Expansion | Legacy Bus Interface |
|---|---|
Use Scenario: Adding GPIO capability to microcontrollers with limited native parallel port pins, such as in industrial PLC modules. IC Role / Device Role / Timing Role: Acts as an 8-bit bidirectional I/O latch with configurable 3-state control, synchronized to host bus cycles via LE and OE. Use Value: Eliminates need for discrete transceivers or level shifters; 48 mA drive supports direct connection to 5 V CMOS/TTL peripherals. | Use Scenario: Interfacing a Z80 or 8086 CPU to shared memory or peripheral address/data buses in vintage computer designs. IC Role / Device Role / Timing Role: Provides registered address latching and bus-isolated data buffering with precise OE-controlled turnarounds. Use Value: Meets strict 13 ns max D→Q delay and 12 ns max OE→Z timing required for sub-4 MHz bus cycles without wait states. |
| Test Equipment Backplane | Industrial Control Register Bank |
Use Scenario: Building modular instrumentation backplanes where multiple cards share a common control bus with isolated signal paths. IC Role / Device Role / Timing Role: Functions as a fault-isolated bus driver/latch, using PRE/CLR to force known states during self-test or error recovery. Use Value: Asynchronous PRE/CLR allows immediate bus reset without halting master controller-reducing diagnostic downtime. | Use Scenario: Storing configuration bits or status flags in programmable logic controllers where register persistence must survive brief power dips. IC Role / Device Role / Timing Role: Serves as a nonvolatile shadow register bank; retains latched data while outputs are tri-stated during reconfiguration. Use Value: Internal latches hold state even when OE is asserted-enabling hot-swap-safe register updates without data corruption. |
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 |
|---|---|---|---|
| SN74ALS573NT | Single OE input (vs. three OE inputs); no PRE/CLR; octal transparent latch only. | Lacks independent bus segmentation and deterministic reset-requires external logic for multi-OE or reset functions. | Select when simplified control suffices and board space is constrained; not suitable for PRE/CLR-critical systems. |
| SN74AS845N | AS-family variant: faster propagation (tPLH = 1.5 ns typ), higher ICC (67 mA max), tighter VCC tolerance (4.75–5.25 V). | Higher speed and power consumption; requires stricter supply regulation and thermal management. | Select for timing-critical bus extensions where <10 ns D→Q delay is mandatory and power budget allows. |
Compared with SN74ALS845NT, SN74ALS573NT reduces control flexibility but saves board area, while SN74AS845N trades power efficiency for speed-making SN74ALS845NT optimal for balanced commercial backplane designs requiring robust reset and segmented bus control.
Availability
SN74ALS845NT is available at Aetrix Electronics and suitable for legacy industrial control systems, test equipment backplanes, and parallel I/O expansion modules requiring stable component supply and long-term obsolescence mitigation support.
Supply support for SN74ALS845NT 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 U.S.-based semiconductor company founded in 1930, specializing in analog, embedded processing, and logic ICs with broad industrial and automotive portfolio coverage.
The SN74ALS845NT belongs to TI's legacy Advanced Low-Power Schottky (ALS) logic family, designed specifically for high-drive, noise-immune bus interface and latching in commercial-grade computing and instrumentation systems.
FAQ
What is the function of the PRE and CLR pins on the SN74ALS845NT?
The PRE (pin 1) and CLR (pin 11) pins on the SN74ALS845NT provide asynchronous set and reset functionality. When PRE is pulled low, all eight Q outputs go high immediately; when CLR is pulled low, all Q outputs go low-regardless of LE state or data inputs. This enables deterministic initialization without waiting for clock edges, making SN74ALS845NT suitable for system reset circuits where immediate output control is required.
Does the SN74ALS845NT support true bidirectional data flow?
No, the SN74ALS845NT does not support true bidirectional data flow. It is an 8-bit transparent D-type latch with noninverting inputs and outputs-data flows unidirectionally from D to Q. While its 3-state outputs allow it to share a bus with other drivers (e.g., in a bidirectional bus system), the SN74ALS845NT itself lacks internal direction control or feedback paths; external logic must manage bus direction separately.
What is the maximum capacitive load the SN74ALS845NT can drive reliably?
The SN74ALS845NT is characterized for CL = 50 pF in switching specifications, but its ±48 mA IOL rating enables reliable driving of loads exceeding 100 pF when combined with proper termination and layout. Real-world performance depends on trace impedance and slew rate constraints; for loads above 80 pF, verify timing margins using the 13 ns max tPLH and 12 ns max tPLZ values under actual board conditions.
Is the SN74ALS845NT RoHS compliant?
No, the SN74ALS845NT is not RoHS compliant. Per TI's 2010 Packaging Addendum, the NT-packaged SN74ALS845NT is marked "OBSOLETE" with "TBD" for Eco Plan, indicating no Pb-Free or RoHS conversion was implemented. It contains leaded solderable leads and is intended for legacy repair and obsolescence-sensitive applications where RoHS compliance is not mandated.
How does the triple OE architecture of the SN74ALS845NT improve bus design?
The triple OE architecture (OE1, OE2, OE3) in the SN74ALS845NT allows independent control of output groups-enabling segmented bus access without external decoding logic. For example, OE1 can gate address bits, OE2 data bits, and OE3 control flags, reducing gate count and propagation delay in complex backplane systems. This feature directly improves timing predictability and simplifies PCB routing compared to single-OE alternatives like the SN74ALS573NT.
SN74ALS845NT 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:
- -
SN74ALS845NT FAQ
1.How can I place an order for SN74ALS845NT through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS845NT 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 SN74ALS845NT reliable?
The price and inventory of SN74ALS845NT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS845NT is usually 5 days.
3.What payment methods are accepted for SN74ALS845NT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS845NT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS845NT?
SN74ALS845NT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS845NT 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 SN74ALS845NT?
For technical support, including SN74ALS845NT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS845NT requirements.
6.How does Aetrix verify that SN74ALS845NT is sourced from the original manufacturer or authorized distributors?
All SN74ALS845NT 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 SN74ALS845NT meets industry standards.
7.What is the process for return or replacement of SN74ALS845NT?
All SN74ALS845NT units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS845NT, 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 SN74ALS845NT part is unused and in its original packaging.
Return procedure for SN74ALS845NT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS845NT Tags
-
SN74LVC1G17DBVR
Texas Instruments
-
SN74LVC1G07DCKR
Texas Instruments
-
SN74LVC1G17DCKR
Texas Instruments
-
SN74LVC1G07DBVR
Texas Instruments
-
SN74LVC1G125DCKR
Texas Instruments
-
SN74AHCT1G126DBVR
Texas Instruments
-
SN74LVC1G125DBVR
Texas Instruments
-
SN74AHCT1G125DBVR
Texas Instruments
-
SN74LVC2G17DBVR
Texas Instruments
-
SN74LVC2G07DCKR
Texas Instruments
-
SN74LVC1G34DCKR
Texas Instruments
-
SN74LVC2G17DCKR
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
