My Inquiry
My Account
Texas Instruments SN74HC645NSRE4
- Part No.:
- SN74HC645NSRE4
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.209", 5.30mm Width)
- Datasheet:
-
SN74HC645NSRE4.pdf
- Description:
- IC TXRX NON-INVERT 6V 20SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,228
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74HC645NSRE4 from Texas Instruments is an octal bus transceiver IC designed for asynchronous two-way data communication between parallel buses. It features 8-bit bidirectional data flow controlled by DIR and OE inputs, operates across 2 V to 6 V, delivers ±6-mA output drive at 5 V, and achieves typical propagation delay of 12 ns - enabling reliable level-shifting and bus isolation in industrial control backplanes.
For engineers reviewing the SN74HC645NSRE4 datasheet, SN74HC645NSRE4 pinout, SN74HC645NSRE4 application, or SN74HC645NSRE4 equivalent, key selection considerations include direction-control logic behavior, 3-state output timing (ten/tdis), thermal resistance (θJA = 60°C/W), and compatibility with LSTTL loads in mixed-voltage systems.
Technical Context
This device implements true CMOS logic with high-current 3-state outputs capable of driving up to 15 LSTTL loads. Its DIR input selects data direction (A→B or B→A), while OE enables or isolates both buses simultaneously - supporting hot-swap and power-managed system architectures.
Electrical operation is defined across 2 V–6 V supply range with guaranteed VIH/VIL thresholds at all voltages, low input current (≤1 µA), and ICC ≤80 µA max. Switching performance is characterized at CL = 50 pF and CL = 150 pF, with tpd = 12 ns (typ) at VCC = 6 V and TA = 25°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - supports interoperability between 3.3 V and 5 V logic domains without level shifters. |
| Output Drive Strength | ±6 mA at 5 V - sufficient to directly interface with standard LSTTL inputs (15-load capacity). |
| Propagation Delay (tpd) | 12 ns typical at VCC = 6 V, CL = 50 pF - enables sub-50 MHz bus operation in synchronous designs. |
| 3-State Enable Time (ten) | 20 ns max at VCC = 6 V - ensures fast bus arbitration and minimal contention window during direction switching. |
| Quiescent Current (ICC) | 80 µA maximum - suitable for low-power embedded systems with extended sleep modes. |
| Input Leakage Current | ±1 µA max - prevents unintended logic transitions when inputs are floating or weakly biased. |
| Power Dissipation Capacitance | 40 pF per transceiver - used to calculate dynamic power consumption under switching conditions. |
Pinout & Package
SN74HC645NSRE4 is housed in a 20-pin SOP (Small Outline Package) with NS suffix, measuring 7.5 mm × 12.8 mm, 1.75 mm height, and 1.27 mm lead pitch. The package is RoHS-compliant, tape-and-reel packaged (2000 units/reel), and rated MSL Level-1 (unlimited floor life).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A-bus inputs/outputs | Bidirectional data terminals connected to source bus; direction determined by DIR state. |
| 11, 13, 14, 15, 16, 17, 18, 19 | B-bus inputs/outputs | Bidirectional data terminals connected to destination bus; mirror A-bus functionality. |
| 9 | GND | Ground reference for all internal circuitry and I/O buffers. |
| 10 | VCC | Positive supply rail (2–6 V); powers all logic and output stages. |
| 12 | OE | Active-low 3-state enable; when high, both A and B ports enter high-impedance state. |
| 20 | DIR | Direction control input; low = B→A transfer, high = A→B transfer. |
Key Features
| Feature | Design Value |
|---|---|
| Wide Supply Range | 2 V to 6 V operation enables direct use in 3.3 V and 5 V systems without external regulators. |
| Bidirectional Data Flow | Single DIR pin controls full 8-bit data path direction - reduces PCB routing complexity vs. dual-unidirectional solutions. |
| High-Current 3-State Outputs | ±6 mA drive at 5 V meets LSTTL fan-out requirements, eliminating need for buffer amplification. |
| Low Power Consumption | 80 µA max ICC allows integration into battery-backed or energy-constrained subsystems. |
| Fast Switching Performance | 12 ns typical tpd at 6 V supports high-speed bus handshaking in real-time control applications. |
Applications
| Industrial Backplane Interface | Microcontroller Bus Expansion |
|---|---|
|
Use Scenario: Isolating and translating data between legacy 5 V PLC modules and modern 3.3 V FPGA-based I/O controllers on shared backplane wiring. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A↔B data flow under DIR-controlled direction and OE-gated isolation. Use Value: Eliminates level-shifter ICs and reduces component count while maintaining signal integrity across voltage domains. |
Use Scenario: Extending GPIO or parallel memory bus from an ARM Cortex-M4 MCU to external SRAM and peripheral ASICs. IC Role / Device Role / Timing Role: Octal transceiver providing configurable data path direction and bus hold-off during DMA transfers. Use Value: Enables deterministic bus arbitration with <20 ns enable/disable timing, preventing read/write collisions. |
| Test Equipment Signal Routing | Automotive Diagnostic Interface |
|
Use Scenario: Dynamically reconfiguring signal paths in automated test equipment (ATE) to route DUT data between multiple instrument channels. IC Role / Device Role / Timing Role: Directionally controllable 8-bit switch supporting hot-plug reconfiguration via microcontroller GPIO. Use Value: Achieves <50 ns total switching latency (tpd + ten), meeting ATE timing calibration requirements. |
Use Scenario: Interfacing a 5 V CAN controller's parallel status/data bus with a 3.3 V automotive microcontroller diagnostic port. IC Role / Device Role / Timing Role: Voltage-tolerant bus transceiver handling bidirectional diagnostics traffic under ISO 11898-3 constraints. Use Value: Maintains noise immunity with 1.8 V VIL margin at 5 V supply and supports 125 kHz diagnostic polling rates. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LVC645APW | Lower VCC range (1.65–3.6 V), higher speed (tpd = 5.4 ns typ), but not 5 V tolerant. | Suitable only for 3.3 V-only systems; cannot replace SN74HC645NSRE4 in mixed 5 V/3.3 V environments. | Select when operating exclusively at 3.3 V and requiring faster timing margins. |
| 74AC645SCX | Wider VCC (2–6 V), higher drive (±24 mA), but higher ICC (4 µA typ) and no 80 µA max guarantee. | Better for driving heavy capacitive loads or long traces, but less optimal for ultra-low-power standby modes. | Choose when output loading exceeds 15 LSTTL units or when AC-series timing consistency is required. |
Compared with SN74HC645NSRE4, SN74LVC645APW offers superior speed in 3.3 V systems but lacks 5 V tolerance, while 74AC645SCX provides stronger drive and broader AC-family timing predictability at the cost of higher static power - making SN74HC645NSRE4 the balanced choice for mixed-voltage, low-quiescent-power industrial interfaces.
Availability
SN74HC645NSRE4 is available at Aetrix Electronics and suitable for industrial backplane interfaces, microcontroller bus expansion, test equipment signal routing, and automotive diagnostic interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for SN74HC645NSRE4 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 connectivity technologies, with over 90 years of innovation in industrial, automotive, and communications markets.
SN74HC645NSRE4 belongs to TI's HC logic family - engineered for robust CMOS performance in noise-prone industrial environments, emphasizing wide voltage operation, low power, and reliable 3-state bus control.
FAQ
What is the maximum operating temperature range for SN74HC645NSRE4?
The SN74HC645NSRE4 is rated for operation from –40°C to +85°C, matching the commercial temperature grade of TI's HC logic family. This range supports deployment in industrial control cabinets, factory automation hardware, and outdoor embedded gateways where ambient temperatures may fluctuate significantly. The NS package's θJA of 60°C/W ensures thermal stability under continuous 6 V operation with typical load conditions.
Does SN74HC645NSRE4 support 5 V logic levels when powered at 3.3 V?
No - SN74HC645NSRE4 does not support 5 V-tolerant inputs when VCC = 3.3 V. Its input thresholds scale with VCC (VIH ≥ 0.7×VCC, VIL ≤ 0.3×VCC), so at 3.3 V supply, VIH ≈ 2.31 V minimum. Applying 5 V signals risks damaging the input stage. For mixed-voltage interfacing, SN74HC645NSRE4 must be powered at the higher voltage domain (e.g., 5 V) or paired with dedicated level translators.
How does the DIR pin affect data flow direction in SN74HC645NSRE4?
In SN74HC645NSRE4, the DIR pin is active-high: when DIR = HIGH, data flows from A-bus pins (1–8) to B-bus pins (11,13–19); when DIR = LOW, data flows from B-bus to A-bus. This bidirectional control occurs only when OE = LOW. If OE = HIGH, both buses enter high-impedance state regardless of DIR state - enabling clean bus arbitration in multi-master systems.
What is the recommended PCB layout practice for SN74HC645NSRE4 decoupling?
TI recommends placing a 0.1 µF ceramic capacitor between VCC (pin 10) and GND (pin 9), located within 3 mm of the package, plus a bulk 4.7 µF tantalum or ceramic capacitor near the power entry point of the board. Avoid shared return paths for high-speed switching currents, and route A/B bus traces with controlled impedance (≈50 Ω) and matched lengths to minimize skew - especially critical when operating above 10 MHz.
Can SN74HC645NSRE4 drive standard TTL loads directly?
Yes - SN74HC645NSRE4 is explicitly characterized to drive up to 15 LSTTL loads, verified by its ±6 mA output drive capability at 5 V and guaranteed VOL ≤ 0.33 V and VOH ≥ 3.7 V under those conditions. This meets the DC interface requirements of 74LS-series devices without external pull-ups or buffers, simplifying legacy system upgrades and reducing BOM cost.
SN74HC645NSRE4 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
SN74HC645NSRE4 FAQ
1.How can I place an order for SN74HC645NSRE4 through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC645NSRE4 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 SN74HC645NSRE4 reliable?
The price and inventory of SN74HC645NSRE4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC645NSRE4 is usually 5 days.
3.What payment methods are accepted for SN74HC645NSRE4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC645NSRE4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC645NSRE4?
SN74HC645NSRE4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC645NSRE4 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 SN74HC645NSRE4?
For technical support, including SN74HC645NSRE4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC645NSRE4 requirements.
6.How does Aetrix verify that SN74HC645NSRE4 is sourced from the original manufacturer or authorized distributors?
All SN74HC645NSRE4 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 SN74HC645NSRE4 meets industry standards.
7.What is the process for return or replacement of SN74HC645NSRE4?
All SN74HC645NSRE4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC645NSRE4, 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 SN74HC645NSRE4 part is unused and in its original packaging.
Return procedure for SN74HC645NSRE4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74HC645NSRE4 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…
