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Home > Products > Integrated Circuits (ICs) > Logic > Buffers, Drivers, Receivers, Transceivers

Texas Instruments SN74HCT645PWRG4

Name: SN74HCT645PWRG4
Brand: Texas Instruments
SKU: SN74HCT645PWRG4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SN74HCT645PWRG4

Manufacturer:: Texas Instruments

Category:: Buffers, Drivers, Receivers, Transceivers

Package:: 20-TSSOP (0.173", 4.40mm Width)

Datasheet:: SN74HCT645PWRG4.pdf

Description:: IC TXRX NON-INVERT 5.5V 20TSSOP

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Product details

Overview

SN74HCT645PWRG4 from Texas Instruments is an octal bus transceiver IC designed for asynchronous two-way data flow between A and B buses in 5-V TTL-compatible digital systems. It features direction control (DIR), 3-state output enable (OE), ±6-mA drive strength at 5 V, 14-ns typical propagation delay, and operates across 4.5 V to 5.5 V. It is used in bidirectional data buffering for microcontroller peripheral interfaces.

For engineers reviewing the SN74HCT645PWRG4 datasheet, SN74HCT645PWRG4 pinout, SN74HCT645PWRG4 application, or SN74HCT645PWRG4 equivalent, key selection criteria include bidirectional bus isolation timing, 3-state output leakage (≤5 µA), TTL-input compatibility, and TSSOP-20 thermal performance (θ_JA = 83°C/W).

Technical Context

This device implements dual 8-bit bidirectional transceivers with independent DIR and OE controls per bus pair. Logic-level translation is not supported - inputs require TTL-compatible thresholds (V_IL ≤ 0.8 V, V_IH ≥ 2.0 V) and outputs swing rail-to-rail within 0.33 V of GND and 3.7 V of V_CC under 6-mA load.

Propagation delay varies with supply voltage and load: t_pd = 14 ns (typ) at V_CC = 5.5 V, CL = 50 pF; increases to 34 ns (max) at V_CC = 5.5 V, CL = 150 pF. Enable/disable times (t_en/t_dis) are specified down to 22 ns (min) for fast bus arbitration.

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage	4.5 V to 5.5 V - ensures compatibility with standard 5-V TTL and CMOS logic rails without level-shifting circuitry.
Propagation Delay	14 ns (typ) at 5.5 V, 50-pF load - enables reliable operation in high-speed 8-bit data paths up to ~35 MHz clock-equivalent rates.
Output Drive	±6 mA at 5 V - directly drives 15 LSTTL loads, eliminating need for external buffer stages in legacy bus designs.
Input Current	≤1 µA max - minimizes loading on upstream drivers and supports clean signal integrity in fan-out-critical applications.
3-State Leakage	≤5 µA max at V_CC = 5.5 V - ensures robust bus isolation during OE-high state, preventing unintended current paths in shared-bus systems.
Operating Temperature	−40°C to +85°C - qualified for industrial-grade embedded control, instrumentation, and communications equipment.
Power Consumption	80 µA max I_CC - enables low-static-power operation in always-on subsystems without thermal derating concerns.

Pinout & Package

TSSOP-20 package (PW), 6.5 mm × 4.4 mm, 1.2 mm max height, lead pitch 0.65 mm, RoHS-compliant NIPDAU finish, MSL Level-1.

Pin/Terminal	Circuit Role	Design Meaning
1, 19–20	A1–A8, B1–B8	Octal bidirectional data terminals - A-side connects to master bus; B-side connects to slave/peripheral bus; direction determined by DIR.
2	DIR	Direction-control input - LOW enables A→B transfer; HIGH enables B→A transfer; TTL-compatible threshold.
3	OE	Output-enable input - LOW activates transceiver; HIGH places all A/B pins in high-impedance state for bus isolation.
10	GND	Ground reference - must be connected to system ground plane; decoupling capacitor required near pin.
20	V_CC	Positive supply - 4.5–5.5 V only; requires local 0.1-µF ceramic bypass capacitor to minimize switching noise.

Key Features

Feature	Design Value
True bidirectional data path	Single DIR pin controls full 8-bit A↔B flow without internal latching - ideal for synchronous and asynchronous bus handshaking.
TTL-compatible inputs	V_IL ≤ 0.8 V / V_IH ≥ 2.0 V - interoperates directly with legacy 74LS, 74ALS, and microcontroller GPIO without interface logic.
High-current 3-state outputs	±6 mA drive into 50-pF load - sustains signal integrity across long PCB traces or multi-drop bus configurations.
Low quiescent power	80 µA max I_CC - reduces system-level standby power and eases thermal management in dense board layouts.
Fast enable/disable timing	t_en = 22 ns (min), t_dis = 23 ns (min) at 5.5 V - supports dynamic bus arbitration in real-time control loops and DMA transfers.

Applications

Industrial PLC Backplane Interface	Microcontroller Peripheral Expansion
Use Scenario: Bidirectional data exchange between a main PLC CPU module and modular I/O cards over a shared 8-bit parallel backplane. IC Role / Device Role / Timing Role: SN74HCT645PWRG4 acts as a direction-controlled bus isolator, enabling read/write cycles without contention; DIR toggled per transaction, OE asserted only during active transfer. Use Value: Eliminates need for discrete direction logic and dual unidirectional buffers, reducing component count and PCB area while maintaining deterministic 14-ns latency.	Use Scenario: Expanding GPIO capability of an ARM Cortex-M0+ MCU via parallel-connected peripheral chips (ADCs, DACs, GPIO expanders) sharing a common data bus. IC Role / Device Role / Timing Role: SN74HCT645PWRG4 serves as a programmable bus gate - DIR set by MCU GPIO to select data direction; OE synchronized with chip-select strobes. Use Value: Enables single MCU port to serve multiple peripherals using time-multiplexed addressing, with guaranteed 3-state isolation preventing bus conflicts during idle periods.
Legacy System Bus Bridge	Test Equipment Data Acquisition Interface
Use Scenario: Interfacing modern FPGA-based controller boards to legacy 8-bit ISA or VMEbus peripherals requiring TTL-level signaling and bidirectional handshake protocols. IC Role / Device Role / Timing Role: SN74HCT645PWRG4 provides level-consistent, low-latency bridging - DIR driven by FPGA control logic; OE tied to bus grant signal. Use Value: Maintains sub-20-ns timing margins required by ISA timing specs while supporting hot-swap-safe 3-state behavior during bus arbitration failures.	Use Scenario: High-reliability data capture in automated test equipment where analog front-end modules communicate digitized samples to a central controller over a shielded parallel bus. IC Role / Device Role / Timing Role: SN74HCT645PWRG4 functions as a noise-immune bus driver - OE controlled by controller to isolate modules during calibration; DIR fixed for unidirectional sample streaming. Use Value: ±6-mA drive ensures robust signal integrity over 15-cm ribbon cables; 1 µA input current prevents loading of precision analog reference lines on adjacent traces.

Industrial PLC Backplane Interface

Microcontroller Peripheral Expansion

Use Scenario: Bidirectional data exchange between a main PLC CPU module and modular I/O cards over a shared 8-bit parallel backplane.

IC Role / Device Role / Timing Role: SN74HCT645PWRG4 acts as a direction-controlled bus isolator, enabling read/write cycles without contention; DIR toggled per transaction, OE asserted only during active transfer.

Use Value: Eliminates need for discrete direction logic and dual unidirectional buffers, reducing component count and PCB area while maintaining deterministic 14-ns latency.

Use Scenario: Expanding GPIO capability of an ARM Cortex-M0+ MCU via parallel-connected peripheral chips (ADCs, DACs, GPIO expanders) sharing a common data bus.

IC Role / Device Role / Timing Role: SN74HCT645PWRG4 serves as a programmable bus gate - DIR set by MCU GPIO to select data direction; OE synchronized with chip-select strobes.

Use Value: Enables single MCU port to serve multiple peripherals using time-multiplexed addressing, with guaranteed 3-state isolation preventing bus conflicts during idle periods.

Legacy System Bus Bridge

Test Equipment Data Acquisition Interface

Use Scenario: Interfacing modern FPGA-based controller boards to legacy 8-bit ISA or VMEbus peripherals requiring TTL-level signaling and bidirectional handshake protocols.

IC Role / Device Role / Timing Role: SN74HCT645PWRG4 provides level-consistent, low-latency bridging - DIR driven by FPGA control logic; OE tied to bus grant signal.

Use Value: Maintains sub-20-ns timing margins required by ISA timing specs while supporting hot-swap-safe 3-state behavior during bus arbitration failures.

Use Scenario: High-reliability data capture in automated test equipment where analog front-end modules communicate digitized samples to a central controller over a shielded parallel bus.

IC Role / Device Role / Timing Role: SN74HCT645PWRG4 functions as a noise-immune bus driver - OE controlled by controller to isolate modules during calibration; DIR fixed for unidirectional sample streaming.

Use Value: ±6-mA drive ensures robust signal integrity over 15-cm ribbon cables; 1 µA input current prevents loading of precision analog reference lines on adjacent traces.

Equivalent & Alternatives

The following parts are listed as comparable options for similar octal bidirectional transceiver applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
SN74HCT245PW	Same pinout, identical electrical specs, but lacks DIR pin - uses separate A→B and B→A enable inputs (OE_A, OE_B).	Requires additional control logic to emulate DIR functionality; better suited for fixed-direction dual-bus architectures.	Select when directional control is implemented externally or when independent A/B gating is preferred over single DIR simplicity.
74LVC245APW	3.3-V only (1.65–3.6 V), lower drive (±24 mA), faster t_pd (5.5 ns typ), higher I_IOZ (10 µA max).	Not compatible with 5-V TTL systems; requires level-shifting if interfacing with legacy 5-V peripherals.	Select for new 3.3-V designs prioritizing speed and lower power; avoid for mixed-voltage or legacy 5-V bus integration.

Compared with SN74HCT645PWRG4, SN74HCT245PW offers identical packaging and voltage tolerance but demands extra control signals, whereas 74LVC245APW delivers superior speed and density at the cost of 5-V interoperability - making SN74HCT645PWRG4 the optimal choice for drop-in replacement in existing 5-V TTL infrastructure.

Availability

SN74HCT645PWRG4 is available at Aetrix Electronics and suitable for industrial PLC backplanes, microcontroller peripheral expansion, legacy bus bridges, and test equipment data acquisition requiring stable component supply and long-term obsolescence management.

Supply support for SN74HCT645PWRG4 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 heritage in industry-standard logic families including 74HCT.

The SN74HCT645PWRG4 belongs to TI's 74HCT high-speed CMOS logic family, engineered specifically for seamless 5-V TTL compatibility, low power, and robust noise immunity in industrial and automotive control systems.

FAQ

What is the maximum capacitive load SN74HCT645PWRG4 can drive while maintaining specified timing?

SN74HCT645PWRG4 is characterized for CL = 50 pF and CL = 150 pF loads. At 5.5 V supply, t_pd remains within spec (≤34 ns) up to 150 pF. Driving >150 pF may increase propagation delay beyond 34 ns and degrade edge rate; for heavier loads, verify timing margins with actual board capacitance and consider adding series termination.

Can SN74HCT645PWRG4 operate reliably at 4.2 V supply?

No - SN74HCT645PWRG4 has a minimum recommended supply voltage of 4.5 V. Operation below 4.5 V violates the recommended operating conditions and risks undefined logic states, increased propagation delay, and failure to meet V_IH/V_IL thresholds. Use only within 4.5 V to 5.5 V range.

Is SN74HCT645PWRG4 pin-compatible with SN74HCT245PW?

Yes - SN74HCT645PWRG4 and SN74HCT245PW share identical TSSOP-20 pinout and footprint. However, pin functions differ: SN74HCT645PWRG4 uses DIR (pin 2) and OE (pin 3), while SN74HCT245PW uses OE_A (pin 1) and OE_B (pin 19). Direct substitution requires PCB-level logic reconfiguration.

Does SN74HCT645PWRG4 support hot-swap insertion into a live 5-V bus?

SN74HCT645PWRG4 is not hot-swap rated. Its absolute maximum ratings allow V_CC = −0.5 V to 7 V, but no built-in current limiting or power-up sequencing protection exists. Insertion into a live bus risks latch-up or damage due to transient currents; always power-cycle the system before replacement.

What is the thermal resistance θ_JA for SN74HCT645PWRG4 in its TSSOP-20 package?

The junction-to-ambient thermal resistance (θ_JA) for SN74HCT645PWRG4 in the PW (TSSOP-20) package is 83°C/W, measured per JEDEC JESD51-7 under standard 1-layer board conditions. For sustained 80-µA I_CC and moderate switching activity, this allows operation up to +85°C ambient without heatsinking.

SN74HCT645PWRG4 Specifications

Product attributes: Attribute value

Manufacturer:: Texas Instruments

Series:: 74HCT

Package/Case:: 20-TSSOP (0.173", 4.40mm 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:: 6mA, 6mA

Voltage - Supply:: 4.5V ~ 5.5V

Operating Temperature:: -40°C ~ 85°C (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 20-TSSOP

SN74HCT645PWRG4 FAQ

1.How can I place an order for SN74HCT645PWRG4 through Aetrix?

Please submit a Request for Quotation (RFQ) for SN74HCT645PWRG4 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 SN74HCT645PWRG4 reliable?

The price and inventory of SN74HCT645PWRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HCT645PWRG4 is usually 5 days.

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SN74HCT645PWRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SN74HCT645PWRG4 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 SN74HCT645PWRG4?

For technical support, including SN74HCT645PWRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HCT645PWRG4 requirements.

6.How does Aetrix verify that SN74HCT645PWRG4 is sourced from the original manufacturer or authorized distributors?

All SN74HCT645PWRG4 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 SN74HCT645PWRG4 meets industry standards.

7.What is the process for return or replacement of SN74HCT645PWRG4?

All SN74HCT645PWRG4 units undergo pre-shipment inspection (PSI). If there is an issue with SN74HCT645PWRG4, 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 SN74HCT645PWRG4 part is unused and in its original packaging.

Return procedure for SN74HCT645PWRG4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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