My Inquiry
My Account
Texas Instruments SN74HCT645PWT
- Part No.:
- SN74HCT645PWT
- Manufacturer:
- Texas Instruments
- Package:
- 20-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
SN74HCT645PWT.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,753
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74HCT645PWT from Texas Instruments is an octal bus transceiver IC designed for asynchronous two-way data communication between A and B buses in 5-V digital systems. It features direction control (DIR), output-enable (OE), ±6-mA drive strength at 5 V, 14-ns typical propagation delay, and TTL-compatible inputs. It is used in bidirectional data buffering for microcontroller peripheral interfaces and memory expansion subsystems.
For engineers reviewing the SN74HCT645PWT datasheet, SN74HCT645PWT pinout, SN74HCT645PWT application, or SN74HCT645PWT equivalent, key selection criteria include 5-V operation, 3-state bidirectional bus isolation, high-current drive capability, low ICC (80 µA max), and TSSOP-20 package compatibility with space-constrained PCB layouts.
Technical Context
The SN74HCT645PWT implements true logic-level translation with TTL-voltage-compatible inputs and CMOS outputs. Its DIR input selects data flow direction (A→B or B→A), while OE independently enables or disables all outputs into high-impedance state-enabling bus isolation without affecting internal logic states.
It operates strictly within 4.5 V to 5.5 V supply range and guarantees performance across −40°C to +85°C. Input leakage is limited to ±1 µA max, and output clamp current is rated ±20 mA, supporting robust interfacing with legacy LSTTL loads (up to 15 per output).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures compatibility with standard 5-V logic rails and tolerance against rail droop. |
| Propagation Delay | 14 ns typ at 5.5 V - enables reliable timing in high-speed 5-V bus systems up to ~35 MHz data rate. |
| Output Drive | ±6 mA at 5 V - directly drives 15 LSTTL loads without external buffers. |
| ICC (Max) | 80 µA - supports low-static-power system design in always-on or battery-backed modules. |
| Input Compatibility | TTL-voltage - accepts standard 0.8 V/2.0 V logic thresholds without level-shifting circuitry. |
| Operating Temperature | −40°C to +85°C - qualified for industrial-grade embedded applications. |
| 3-State Leakage | ±10 µA max IOZ - minimizes bus contention risk during output disable. |
Pinout & Package
TSSOP-20 package: 4.4 mm × 6.5 mm body, 0.65 mm lead pitch, 1.2 mm max height, moisture sensitivity level 1 (260°C reflow compatible).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (DIR) | Direction Control Input | High = A-to-B data transfer; Low = B-to-A transfer - determines real-time bus flow polarity. |
| 2–9 (A1–A8) | A-Bus Data Inputs/Outputs | Bidirectional I/O pins connected to A-side system bus; high-impedance when OE = high. |
| 10 (GND) | Ground Reference | Primary return path for logic and output currents; must be low-inductance connection. |
| 11 (VCC) | Power Supply | 4.5–5.5 V supply input; requires local 0.1-µF ceramic decoupling adjacent to pin. |
| 12 (OE) | Output Enable Input | Low = outputs active; High = all A/B pins enter high-Z - enables bus sharing and hot-swap isolation. |
| 13–20 (B1–B8) | B-Bus Data Inputs/Outputs | Bidirectional I/O pins connected to B-side bus; functionally mirrored with A pins under DIR control. |
Key Features
| Feature | Design Value |
|---|---|
| Asynchronous Bidirectional Transfer | Enables real-time A↔B data routing without clock synchronization - ideal for glue logic in microcontroller co-processor links. |
| Independent DIR and OE Control | Allows simultaneous direction setting and output gating - supports dynamic bus arbitration and power-aware sleep modes. |
| High-Current 3-State Outputs | ±6 mA drive at 5 V eliminates need for external bus drivers in LSTTL-interfaced systems. |
| Low Input Current | ≤1 µA max II - reduces loading on upstream logic and preserves fanout margin in cascaded buffer chains. |
| TTL-Compatible Inputs | VIH = 2.0 V min, VIL = 0.8 V max - interoperates directly with legacy 5-V TTL, LS-TTL, and HCT-family devices. |
Applications
| Microcontroller Peripheral Expansion | Memory Bus Isolation |
|---|---|
Use Scenario: Expanding GPIO count of an MCU by connecting parallel peripherals (e.g., LCD controllers, ADCs) via shared 8-bit data bus. IC Role / Device Role / Timing Role: SN74HCT645PWT acts as a bidirectional data shuttle between MCU port and peripheral bus, controlled by MCU's DIR and OE signals. Use Value: Eliminates need for separate transmit/receive buffers; enables full-duplex peripheral access using single 8-bit bus lane. | Use Scenario: Isolating SRAM or EPROM address/data buses from CPU during DMA or debug probe operations. IC Role / Device Role / Timing Role: SN74HCT645PWT serves as a controllable bus barrier - OE deactivation disconnects memory bus electrically while preserving signal integrity. Use Value: Prevents bus contention during memory access arbitration; supports safe in-circuit debugging without hardware modification. |
| FPGA-to-Microcontroller Interface | Legacy System Bus Bridging |
Use Scenario: Interfacing a 5-V FPGA I/O bank with an 8-bit microcontroller having limited native drive strength. IC Role / Device Role / Timing Role: SN74HCT645PWT provides level-consistent, high-drive bidirectional data path between FPGA and MCU, synchronized only by control signals. Use Value: Resolves fanout and voltage-margin limitations of FPGA I/Os driving MCUs - no external level shifters or series resistors required. | Use Scenario: Connecting modern microcontrollers to legacy 5-V parallel peripherals (e.g., printers, industrial I/O modules) with mismatched drive capability. IC Role / Device Role / Timing Role: SN74HCT645PWT functions as a protocol-transparent bus repeater - translating drive strength and noise immunity without altering data content. Use Value: Extends usable life of legacy equipment by enabling drop-in replacement of obsolete transceivers with identical pinout and timing behavior. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bidirectional bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT245PW | Same logic function, identical pinout, same TSSOP-20 package; differs only in top-side marking (HCT245 vs HT645). | No functional difference - both meet identical HCT family specs and are interchangeable in all designs using SN74HCT645PWT. | Select SN74HCT245PW if sourcing flexibility or dual-source qualification is required; identical electrical and thermal behavior. |
| 74LCX245MTCX | Lower VCC range (2.0–3.6 V); not 5-V compatible; uses different input threshold specs and has higher speed (tPD ≈ 5.5 ns). | Requires system-level voltage redesign; unsuitable for direct 5-V replacement but preferred in mixed-voltage 3.3-V domains with tighter timing budgets. | Choose 74LCX245MTCX only for new 3.3-V designs prioritizing speed and lower power - not a drop-in substitute for SN74HCT645PWT. |
Compared with SN74HCT245PW, the SN74HCT645PWT offers identical functionality and pin compatibility, making it a direct second-source option; versus 74LCX245MTCX, it provides guaranteed 5-V interoperability and TTL input compatibility at the cost of higher supply voltage requirement and slightly longer propagation delay.
Availability
SN74HCT645PWT is available at Aetrix Electronics and suitable for industrial control panels, embedded instrumentation, and legacy-system upgrade projects requiring stable component supply and long-term manufacturability.
Supply support for SN74HCT645PWT 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 solutions for industrial, automotive, and communications markets.
The SN74HCT645PWT belongs to TI's 74HCT logic family, engineered for TTL-compatible 5-V digital systems requiring robust noise immunity, low power consumption, and seamless integration with legacy and modern microcontrollers.
FAQ
What is the maximum operating temperature range for the SN74HCT645PWT?
The SN74HCT645PWT is rated for operation from −40°C to +85°C. This industrial temperature range ensures reliable performance in embedded control systems, factory automation equipment, and outdoor instrumentation where ambient conditions vary significantly. The device maintains specified timing and drive characteristics across this full range, as validated in TI's recommended operating conditions table.
Does the SN74HCT645PWT require external pull-up or pull-down resistors on DIR or OE pins?
No, the SN74HCT645PWT does not require external pull-up or pull-down resistors on DIR or OE. Its input leakage current is ≤±1 µA, and inputs are TTL-voltage compatible with defined VIH (≥2.0 V) and VIL (≤0.8 V) thresholds. However, TI recommends tying unused control inputs to VCC or GND to prevent floating states that could cause undefined output behavior or increased ICC.
Can the SN74HCT645PWT interface directly with 3.3-V logic devices?
The SN74HCT645PWT is not designed for direct 3.3-V logic interfacing. Its inputs require VIH ≥2.0 V and VIL ≤0.8 V - compatible with 3.3-V CMOS outputs - but its outputs swing rail-to-rail (0 V to VCC), so a 5-V-powered SN74HCT645PWT produces 5-V logic highs. Direct connection to 3.3-V-only inputs risks overvoltage damage unless current-limiting or level-shifting circuitry is added.
What is the thermal resistance (θJA) of the SN74HCT645PWT in its TSSOP-20 package?
The SN74HCT645PWT in the TSSOP-20 (PW) package has a junction-to-ambient thermal resistance (θJA) of 83°C/W, as specified in TI's absolute maximum ratings table. This value assumes standard JEDEC test board conditions (single-layer copper, 1-in² pad). For thermally constrained layouts, designers should verify junction temperature using actual power dissipation (ICC × VCC + switching losses) and ensure TJ remains below 125°C.
Is the SN74HCT645PWT pin-compatible with other members of the 74HCT transceiver family?
Yes, the SN74HCT645PWT is pin-compatible with SN74HCT245PW and SN74HCT245PWR in the same TSSOP-20 package. All share identical pin assignments for DIR, OE, A1–A8, B1–B8, VCC, and GND. Functional equivalence is confirmed by TI's ordering information table and logic diagrams - enabling direct substitution without PCB changes in existing designs.
SN74HCT645PWT 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:
- Discontinued at Digi-Key
- 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
SN74HCT645PWT FAQ
1.How can I place an order for SN74HCT645PWT through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HCT645PWT 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 SN74HCT645PWT reliable?
The price and inventory of SN74HCT645PWT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HCT645PWT is usually 5 days.
3.What payment methods are accepted for SN74HCT645PWT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HCT645PWT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HCT645PWT?
SN74HCT645PWT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HCT645PWT 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 SN74HCT645PWT?
For technical support, including SN74HCT645PWT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HCT645PWT requirements.
6.How does Aetrix verify that SN74HCT645PWT is sourced from the original manufacturer or authorized distributors?
All SN74HCT645PWT 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 SN74HCT645PWT meets industry standards.
7.What is the process for return or replacement of SN74HCT645PWT?
All SN74HCT645PWT units undergo pre-shipment inspection (PSI). If there is an issue with SN74HCT645PWT, 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 SN74HCT645PWT part is unused and in its original packaging.
Return procedure for SN74HCT645PWT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74HCT645PWT 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…
