My Inquiry
My Account
Texas Instruments SN74HC645DW
- Part No.:
- SN74HC645DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74HC645DW.pdf
- Description:
- IC TXRX NON-INVERT 6V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:204
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74HC645DW 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 use in industrial control backplanes and legacy microprocessor data bus interfaces.
For engineers reviewing the SN74HC645DW datasheet, SN74HC645DW pinout, SN74HC645DW application, or SN74HC645DW equivalent, key selection criteria include direction-control logic behavior, 3-state output isolation timing (ten/tdis), high-current drive capability into LSTTL loads, and SOIC-20 package compatibility with automated SMT assembly.
Technical Context
The SN74HC645DW implements true CMOS logic with Schmitt-trigger–free inputs and complementary MOSFET output stages. Its DIR input selects data flow direction (A→B or B→A), while OE enables/disables all outputs simultaneously into high-impedance state - supporting bus sharing without contention.
It uses standard HC-series silicon process with rail-to-rail input voltage tolerance (0 V to VCC) and guaranteed operation over –40°C to +85°C. Absolute maximum ratings include ±35 mA continuous output current and 70 mA total supply current, ensuring robustness in mixed-signal board environments with shared ground planes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2 V to 6 V - supports direct interface with 3.3 V and 5 V logic families without level shifters. |
| Propagation Delay (tpd) | 12 ns typical at VCC = 6 V - enables reliable operation up to ~40 MHz bus toggle rates under light capacitive load. |
| Output Drive Strength | ±6 mA at VCC = 5 V - sufficient to drive 15 LSTTL loads, eliminating need for external buffer stages. |
| Quiescent Current (ICC) | 80 µA max - minimizes standby power in battery-backed or energy-sensitive systems. |
| Input Leakage Current | 1 µA max - ensures stable logic levels even with high-impedance pull-ups or long trace stubs. |
| Enable/Disable Time (ten/tdis) | 20 ns / 21 ns typical at VCC = 6 V - guarantees clean bus arbitration during dynamic reconfiguration. |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded applications including PLC I/O modules. |
Pinout & Package
SN74HC645DW is housed in a 20-pin SOIC (DW) package with 1.27 mm pitch, 7.6 mm body width, and 2.65 mm max height - compatible with IPC-7351 SOIC-20 footprint and standard reflow profiles (MSL Level-1).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A-bus inputs/outputs | Bidirectional data terminals connected to A-side bus; direction determined by DIR state. |
| 11, 13, 14, 15, 16, 17, 18, 19 | B-bus inputs/outputs | Bidirectional data terminals connected to B-side bus; functionally mirrored to A pins. |
| 9 | GND | Power return reference for all internal logic and output drivers. |
| 10 | VCC | Positive supply rail (2–6 V); decoupling capacitor required within 10 mm. |
| 12 | OE | Active-low output enable; drives all A/B pins to high-Z when high. |
| 20 | DIR | Direction control; low = B→A transfer, high = A→B transfer. |
Key Features
| Feature | Design Value |
|---|---|
| True bidirectional bus interface | Single DIR pin configures full 8-bit data path direction without external logic or multiplexers. |
| High-current 3-state outputs | ±6 mA drive at 5 V eliminates need for discrete bus buffers in multi-drop configurations. |
| Low power consumption | 80 µA max ICC allows integration into always-on subsystems without thermal derating. |
| Rail-to-rail input compatibility | Accepts VIH/VIL thresholds scaling with VCC - simplifies mixed-voltage system design. |
| SOIC-20 surface-mount package | Standardized footprint supports automated placement and reflow; JEDEC MS-013 compliant. |
Applications
| Industrial Backplane Interface | Legacy Microprocessor Bus Extension |
|---|---|
Use Scenario: Isolating and extending data paths between CPU module and I/O expansion cards in programmable logic controllers. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing 8-bit parallel data exchange under microcontroller control via DIR/OE signals. Use Value: Enables hot-swap-capable modular architecture by electrically isolating bus segments during card insertion/removal. | Use Scenario: Interfacing Z80 or 8085-based peripheral boards with main system bus operating at 4–6 MHz. IC Role / Device Role / Timing Role: Direction-controlled data bridge synchronizing read/write cycles between processor and memory-mapped peripherals. Use Value: Meets strict tpd ≤ 12 ns requirement for cycle-accurate timing in 4 MHz CPU designs with 200 ns minimum bus access time. |
| Test Equipment Signal Routing | Automated Test Fixture Control |
Use Scenario: Dynamically rerouting DUT data lines between measurement instruments and stimulus sources in ATE platforms. IC Role / Device Role / Timing Role: Reconfigurable bus coupler allowing software-defined signal path selection without mechanical relays. Use Value: Reduces test setup latency by replacing electromechanical switches with sub-20 ns digital enable/disable transitions. | Use Scenario: Controlling multiple sensor acquisition channels on a single PCB where analog front-ends share digital control lines. IC Role / Device Role / Timing Role: Isolation gate preventing crosstalk between independent ADC/DAC control buses during concurrent sampling. Use Value: Eliminates inter-channel interference caused by simultaneous SPI/I²C writes, verified via <100 mV noise margin at 100 kHz switching. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT645DW | TTL-compatible input thresholds (VIH = 2 V min at VCC = 4.5 V); identical pinout and timing. | Better suited for mixed 5 V TTL/CMOS systems where input noise immunity is critical. | Select SN74HCT645DW when interfacing with legacy 74LS devices or noisy industrial environments. |
| 74LCX645MTCX | Lower VCC range (2.0–3.6 V), higher speed (tpd = 5.5 ns), and 5 V tolerant inputs; TSSOP-20 package. | Optimized for 3.3 V-only systems requiring faster throughput and smaller footprint. | Choose 74LCX645MTCX for space-constrained portable instrumentation with 3.3 V supply rails. |
Compared with SN74HC645DW, SN74HCT645DW offers improved noise margin in 5 V TTL environments but consumes slightly more quiescent current, while 74LCX645MTCX provides superior speed and density at the cost of reduced voltage flexibility and non-SOIC packaging.
Availability
SN74HC645DW is available at Aetrix Electronics and suitable for industrial control backplanes, legacy microprocessor bus extensions, and automated test fixture control requiring stable component supply across extended product lifecycles.
Supply support for SN74HC645DW 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 company headquartered in Dallas, Texas, delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74HC645DW belongs to TI's 74HC logic family - engineered for high-speed, low-power, pin-compatible replacements of legacy TTL devices in industrial and commercial applications.
FAQ
What is the maximum clock frequency supported by SN74HC645DW in a data bus application?
The SN74HC645DW does not contain an internal clock; it is an asynchronous transceiver. Its usable data rate depends on propagation delay (tpd = 12 ns typical at 6 V) and bus loading. For a 50 pF load, it supports reliable toggling up to approximately 40 MHz in point-to-point configurations, assuming proper termination and layout practices. System-level timing must account for worst-case tpd, ten, and tdis values per the datasheet.
Does SN74HC645DW support hot-swapping of connected bus segments?
Yes - the SN74HC645DW supports hot-swap operation when OE is asserted high before physical insertion/removal. Its 3-state outputs isolate both A and B buses during transition, preventing signal contention. However, external series resistors (e.g., 10–33 Ω) on data lines and controlled slew-rate PCB routing are recommended to suppress ESD-induced glitches during plug-in events involving SN74HC645DW.
Can SN74HC645DW operate reliably at 3.3 V supply voltage?
Yes - the SN74HC645DW is fully specified from 2 V to 6 V, including 3.3 V operation. At VCC = 3.3 V, it delivers ±4 mA output drive, maintains VIH = 2.31 V and VIL = 0.99 V thresholds, and achieves tpd ≈ 16 ns (typical). All DC and AC parameters remain valid per the recommended operating conditions table in the SN74HC645DW datasheet.
What is the thermal resistance (θJA) of the SN74HC645DW SOIC package?
The junction-to-ambient thermal resistance (θJA) for the SN74HC645DW in its SOIC (DW) package is 58°C/W, measured under JEDEC JESD 51-7 standard conditions (single-layer 1-in² copper pad, no airflow). This value assumes minimal PCB copper area; actual thermal performance improves significantly with internal ground/power planes and thermal vias beneath the package body.
Is SN74HC645DW pin-compatible with SN74LS645N?
No - although both are octal transceivers, SN74HC645DW (SOIC-20) and SN74LS645N (PDIP-20) differ in pin mapping: DIR is on pin 20 for SN74HC645DW but on pin 1 for SN74LS645N, and OE is on pin 12 versus pin 11. Additionally, LS logic requires different biasing and has incompatible drive strength. Direct replacement requires PCB redesign and logic-level validation.
SN74HC645DW Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74HC
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Bulk
- 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-SOIC
SN74HC645DW FAQ
1.How can I place an order for SN74HC645DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC645DW 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 SN74HC645DW reliable?
The price and inventory of SN74HC645DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC645DW is usually 5 days.
3.What payment methods are accepted for SN74HC645DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC645DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC645DW?
SN74HC645DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC645DW 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 SN74HC645DW?
For technical support, including SN74HC645DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC645DW requirements.
6.How does Aetrix verify that SN74HC645DW is sourced from the original manufacturer or authorized distributors?
All SN74HC645DW 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 SN74HC645DW meets industry standards.
7.What is the process for return or replacement of SN74HC645DW?
All SN74HC645DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC645DW, 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 SN74HC645DW part is unused and in its original packaging.
Return procedure for SN74HC645DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74HC645DW 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…
