My Inquiry
My Account
Texas Instruments SN74HC645NSR
- Part No.:
- SN74HC645NSR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74HC645NSR.pdf
- Description:
- IC TXRX NON-INVERT 6V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,590
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74HC645NSR from Texas Instruments is an octal bus transceiver IC designed for asynchronous two-way data communication between parallel buses. It features bidirectional data flow controlled by DIR, 3-state outputs enabled/disabled by OE, operates from 2 V to 6 V, delivers ±6 mA output drive at 5 V, and achieves typical propagation delay of 12 ns at 6 V - enabling reliable level-shifting and bus isolation in industrial control backplanes.
For engineers reviewing the SN74HC645NSR datasheet, SN74HC645NSR pinout, SN74HC645NSR application, or SN74HC645NSR equivalent, this device supports critical design tasks including bidirectional I/O buffering, microcontroller peripheral bus expansion, and legacy TTL-to-CMOS interface translation with verified 15-LSTTL load drive capability.
Technical Context
This device implements true CMOS logic with symmetrical input thresholds and rail-to-rail output swing. Its dual-control architecture uses DIR to select A→B or B→A data direction and OE to place all outputs in high-impedance state - enabling dynamic bus arbitration without external logic.
Each of the eight channels includes independent 3-state output drivers with ±35 mA absolute maximum continuous output current and ±20 mA clamp current. Input leakage remains ≤1 µA across full temperature range, supporting low-power standby modes in battery-backed systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - enables direct interfacing with 3.3 V and 5 V logic families without level shifters. |
| Propagation Delay (tpd) | 12 ns typical at VCC = 6 V, CL = 50 pF - ensures timing compatibility with 40-MHz bus cycles. |
| Output Drive Strength | ±6 mA at VCC = 5 V - drives up to 15 LSTTL loads per channel, eliminating need for buffer fanout stages. |
| Input Leakage Current | ≤1 µA max - minimizes static power draw and prevents unintended logic transitions on floating inputs. |
| 3-State Enable/Disable Time | ten = 20 ns, tdis = 21 ns at VCC = 6 V - guarantees clean bus release during hot-swap or multiplexer switching. |
| Power Consumption (ICC) | 80 µA max at VCC = 6 V - supports ultra-low-quiescent-current system designs. |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded applications including PLC I/O modules. |
Pinout & Package
SN74HC645NSR is housed in a 20-pin SOP (Small Outline Package) with 0.65 mm lead pitch and 7.5 mm body width, compliant with JEDEC MS-013 and RoHS standards. The package supports surface-mount reflow assembly with MSL Level-1 rating.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | High = A→B data transfer; Low = B→A transfer - determines real-time bus traffic direction without software overhead. |
| 2–9 (A1–A8) | Bus A Data Inputs/Outputs | Bidirectional I/O pins connected to primary system bus; function as inputs when DIR = Low and OE = Low. |
| 10 (GND) | Ground Reference | Primary return path for all internal logic and output drivers; must be low-impedance to minimize ground bounce. |
| 11 (VCC) | Power Supply | CMOS core supply pin; requires local 0.1 µF ceramic decoupling within 5 mm of pin for noise immunity. |
| 12 (OE) | Output Enable Input | Active-Low control: OE = Low enables transceiver; OE = High places all A/B pins in high-Z state for bus isolation. |
| 13–20 (B1–B8) | Bus B Data Inputs/Outputs | Bidirectional I/O pins connected to secondary bus; mirror A-side functionality with opposite directionality. |
Key Features
| Feature | Design Value |
|---|---|
| Bidirectional Data Flow | Single DIR pin selects A→B or B→A path - eliminates need for separate transmit/receive buffers in half-duplex interfaces. |
| True CMOS Logic Levels | VIH = 3.15 V / VIL = 1.35 V at VCC = 4.5 V - ensures robust noise margin (>1.3 V) against EMI in noisy industrial environments. |
| Low-Power 3-State Outputs | IOZ ≤ 5 µA max at VCC = 6 V - prevents bus contention leakage current from disrupting adjacent powered-down subsystems. |
| Wide Input Transition Tolerance | ∆t/∆v ≤ 400 ns/V at VCC = 6 V - accommodates slow-rising signals from mechanical switches or legacy microcontrollers. |
| Thermal Performance | θJA = 60°C/W for NS package - allows operation at full speed up to +85°C ambient without heatsinking in compact enclosures. |
Applications
| Industrial PLC Backplane Interface | Microcontroller Peripheral Expansion |
|---|---|
Use Scenario: Isolating CPU bus from modular I/O cards in programmable logic controllers using shared backplane wiring. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing data exchange between ARM Cortex-M7 host and isolated digital I/O modules. Use Value: Enables hot-swappable card insertion via OE-controlled bus isolation while maintaining <12 ns timing integrity across 8-bit data paths. |
Use Scenario: Expanding GPIO count of an STM32F407 MCU to drive multiple SPI peripherals sharing a common clock domain. IC Role / Device Role / Timing Role: Level-translating and direction-controlling buffer between MCU's native 3.3 V bus and 5 V sensor array interface. Use Value: Delivers ±6 mA drive strength to overcome capacitive loading of long PCB traces, ensuring reliable signal integrity at 25 MHz SPI rates. |
| Legacy System Bus Bridge | Test Equipment Signal Routing |
Use Scenario: Interfacing modern FPGA-based controller boards with vintage 8086-based instrumentation chassis using TTL-compatible signaling. IC Role / Device Role / Timing Role: Asynchronous bidirectional translator converting HC logic levels to LSTTL voltage thresholds without external resistors. Use Value: Drives 15 LSTTL loads directly - eliminates discrete transistor arrays and reduces BOM count in retrofit upgrade kits. |
Use Scenario: Dynamic signal routing matrix in automated test equipment where DUT interface lines must be reconfigured per test sequence. IC Role / Device Role / Timing Role: Programmable bus isolator controlled by FPGA GPIOs to enable/disable signal paths between measurement instruments and device under test. Use Value: Achieves sub-25 ns enable/disable times - supports rapid test mode switching without signal glitches or bus contention. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT645NSR | CMOS input with TTL-compatible thresholds (VIH = 2 V min); identical pinout and timing. | Better suited for mixed 5 V TTL/CMOS systems where input noise immunity must match legacy TTL logic families. | Select when interfacing with older 5 V microcontrollers or logic families requiring guaranteed 2 V VIH. |
| 74LCX645MTCX | Lower VCC range (2.0–3.6 V), higher speed (tpd = 5.5 ns @ 3.3 V), different pinout (TSSOP-20). | Optimized for 3.3 V-only portable/embedded systems requiring minimal propagation delay and lower power. | Choose for new 3.3 V designs prioritizing speed and quiescent current over 5 V compatibility or drop-in replacement. |
Compared with SN74HC645NSR, SN74HCT645NSR offers superior noise immunity in 5 V mixed-signal environments, while 74LCX645MTCX provides faster performance and lower voltage operation but requires PCB layout revision due to TSSOP packaging and non-identical pin mapping.
Availability
SN74HC645NSR is available at Aetrix Electronics and suitable for industrial automation, test equipment, and embedded control applications requiring stable component supply, long-term lifecycle support, and RoHS-compliant sourcing.
Supply support for SN74HC645NSR 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 decades of expertise in high-reliability logic families and industrial interface ICs.
The SN74HC645NSR belongs to TI's 74HC high-speed CMOS logic series, engineered for robust bidirectional bus interfacing in harsh electrical environments where noise immunity, wide voltage operation, and predictable timing are essential.
FAQ
What is the maximum operating temperature range for SN74HC645NSR?
The SN74HC645NSR is rated for operation from –40°C to +85°C, meeting industrial temperature requirements. This range is validated per TI's recommended operating conditions and supported by thermal characterization data showing θJA = 60°C/W for the NS package, enabling reliable performance in enclosed control cabinets without forced cooling.
Does SN74HC645NSR support 3.3 V logic levels?
Yes, SN74HC645NSR fully supports 3.3 V operation: its 2 V to 6 V supply range includes 3.3 V nominal, and input thresholds scale proportionally (VIH = 2.31 V min, VIL = 0.99 V max at VCC = 3.3 V). Output VOH/VOL specifications guarantee clean interfacing with standard 3.3 V CMOS receivers.
Can SN74HC645NSR replace SN74LS645 in existing designs?
SN74HC645NSR can functionally replace SN74LS645 in most cases but requires verification of voltage compatibility: SN74LS645 is 5 V only and draws significantly more current. SN74HC645NSR operates at 5 V with 80 µA ICC versus LS645's ~30 mA, reducing heat and enabling direct substitution if board layout accommodates SOIC-20 footprint and no pull-up resistors are present on OE/DIR.
What is the meaning of "NSR" in SN74HC645NSR?
The "NSR" suffix denotes the specific packaging and packaging format: "NS" indicates the SOP-20 (Small Outline Package) variant per TI's package coding, and "R" signifies tape-and-reel packaging (2000 units per reel). This matches TI's official ordering information where SN74HC645NSR is listed as active, RoHS-compliant, and supplied in large tape-and-reel format.
How does the DIR pin affect data flow direction in SN74HC645NSR?
In SN74HC645NSR, the DIR pin controls real-time data path direction: when DIR = High, data flows from A-bus inputs to B-bus outputs; when DIR = Low, data flows from B-bus inputs to A-bus outputs. This bidirectional control occurs independently of OE state - enabling dynamic direction switching even while outputs remain enabled.
SN74HC645NSR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 20-SOIC (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Logic Type:
- Transceiver, Non-Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 7.8mA, 7.8mA
- Voltage - Supply:
- 2V ~ 6V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
SN74HC645NSR FAQ
1.How can I place an order for SN74HC645NSR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC645NSR 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 SN74HC645NSR reliable?
The price and inventory of SN74HC645NSR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC645NSR is usually 5 days.
3.What payment methods are accepted for SN74HC645NSR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC645NSR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC645NSR?
SN74HC645NSR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC645NSR 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 SN74HC645NSR?
For technical support, including SN74HC645NSR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC645NSR requirements.
6.How does Aetrix verify that SN74HC645NSR is sourced from the original manufacturer or authorized distributors?
All SN74HC645NSR 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 SN74HC645NSR meets industry standards.
7.What is the process for return or replacement of SN74HC645NSR?
All SN74HC645NSR units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC645NSR, 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 SN74HC645NSR part is unused and in its original packaging.
Return procedure for SN74HC645NSR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74HC645NSR 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…
