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Texas Instruments SN74HC640DW
- Part No.:
- SN74HC640DW
- Manufacturer:
- Texas Instruments
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
SN74HC640DW.pdf
- Description:
- IC TRANSCEIVER INVERT 6V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,150
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Product details
Overview
SN74HC640DW from Texas Instruments is an octal bus transceiver with 3-state outputs, designed for bidirectional data transfer between two 8-bit buses in asynchronous systems. It features inverting logic, operates from 2V to 6V, delivers ±4-mA output drive at 5V, and achieves typical propagation delay of 8ns (CL = 50 pF, VCC = 6V), enabling use in industrial control backplanes and legacy microprocessor data bus interfaces.
For engineers reviewing the SN74HC640DW datasheet, SN74HC640DW pinout, SN74HC640DW application, or SN74HC640DW equivalent, key selection criteria include its 20-pin SOIC (DW) package, DIR/OE dual-control architecture, 3-state isolation capability, and compatibility with LSTTL load levels up to 10 units.
Technical Context
The SN74HC640DW implements a fully synchronous octal transceiver function where all eight channels share common direction (DIR) and output-enable (OE) controls. Its inverting logic path ensures signal polarity inversion during A→B or B→A transmission, and its 3-state outputs provide high-impedance isolation when OE is high.
Electrical behavior is defined across 2V–6V supply range with guaranteed operation at –40°C to +85°C. Input thresholds scale with VCC (VIH = 0.7×VCC min, VIL = 0.3×VCC max), and output drive meets ±4 mA at 5V while maintaining low ICC ≤ 80 µA - supporting low-power bus buffering without compromising switching speed.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage Range | 2V to 6V - supports mixed-voltage system interfacing and battery-backed operation down to 2V. |
| Propagation Delay (tpd) | 8ns typical at VCC = 6V, CL = 50 pF - enables reliable timing in 12.5 MHz+ bus cycles. |
| Output Drive Strength | ±4 mA at VCC = 5V - sufficient to directly drive 10 LSTTL loads without external buffers. |
| 3-State Leakage (IOZ) | ±10 µA max at VCC = 6V - ensures minimal bus contention during isolation mode. |
| Input Current (II) | ±1 µA max - eliminates need for pull-up/pull-down resistors on unused control pins. |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded systems and automation equipment. |
| Power Dissipation Cap. (Cpd) | 40 pF - allows accurate dynamic power estimation under switching conditions. |
Pinout & Package
SN74HC640DW is housed in a 20-pin SOIC (DW) package measuring 12.80 mm × 7.50 mm with maximum height of 2.65 mm, RoHS-compliant NIPDAU lead finish, and JEDEC MS-013 registration.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A-side inputs/outputs | Bidirectional data terminals for first bus; driven high/low or placed in high-Z per DIR/OE state. |
| 9 | GND | Ground reference for all internal logic and I/O structures. |
| 10, 11, 12, 13, 14, 15, 16, 17 | B-side inputs/outputs | Bidirectional data terminals for second bus; inverted relative to A-side per functional mode. |
| 18 | VCC | Positive supply rail (2V–6V); requires local 0.1-µF bypass capacitor. |
| 19 | DIR | Direction control input: LOW enables B→A transfer, HIGH enables A→B transfer. |
| 20 | OE | Output enable input: LOW activates transceiver, HIGH places all outputs in high-Z state. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting transceiver logic | Ensures signal polarity inversion across both A→B and B→A paths, simplifying level-shifting in differential bus architectures. |
| Common DIR/OE control | Enables atomic bus direction switching and simultaneous channel enable/disable - critical for glitch-free bus arbitration. |
| High-current 3-state outputs | Delivers ±4 mA at 5V while maintaining <0.33 V VOL under 6 mA sink - guarantees clean TTL-compatible logic levels. |
| Low static current | ICC ≤ 80 µA max eliminates thermal concerns in dense PCB layouts and extends battery life in portable instrumentation. |
| Input transition time tolerance | Accepts slow edges up to 1000 ns at VCC = 2V - accommodates RC-filtered control signals without added Schmitt triggers. |
Applications
| Industrial Backplane Interface | Legacy Microprocessor Bus Extension |
|---|---|
Use Scenario: Isolating and extending parallel address/data buses between PLC CPU and I/O expansion modules over 15 cm traces. IC Role / Device Role / Timing Role: Bidirectional bus transceiver managing A→B and B→A data flow under microcontroller DIR control, with OE used for hot-swap arbitration. Use Value: 8ns tpd and ±4 mA drive ensure setup/hold timing margins are maintained across extended traces, while 3-state isolation prevents bus contention during module insertion/removal. | Use Scenario: Interfacing Z80 or 8085 CPU data bus to peripheral ASICs operating at different voltage domains (e.g., 5V CPU ↔ 3.3V peripheral). IC Role / Device Role / Timing Role: Level-translating octal transceiver providing controlled direction switching and bus isolation via shared DIR/OE lines synchronized to CPU control signals. Use Value: Wide 2V–6V supply range allows direct connection to either side's VCC, eliminating external level shifters; inverting logic matches native Z80 bus protocol conventions. |
| Test Equipment Data Acquisition Bus | Automated Test Fixture Control |
Use Scenario: Multiplexing sensor data streams from 8-channel ADCs into a central FPGA controller using shared parallel bus infrastructure. IC Role / Device Role / Timing Role: Time-multiplexed bus transceiver enabling sequential readout of multiple ADC banks while maintaining electrical isolation between active/inactive banks. Use Value: Low IOZ (±10 µA) and high off-state impedance prevent crosstalk between channels; 40 pF Cpd enables precise dynamic power modeling during burst-mode acquisition. | Use Scenario: Controlling 8-bit DUT interface lines (e.g., JTAG TDI/TDO, SPI MOSI/MISO, GPIO) from a master test controller in production ATE systems. IC Role / Device Role / Timing Role: Programmable bus buffer that adapts DUT pin direction dynamically via DIR and disables entire port via OE during test sequence transitions. Use Value: Single-cycle direction change (enabled by DIR toggle) and sub-50 ns disable time (tdis = 32 ns @ 6V) eliminate test dead time; ±1 µA II reduces control-line loading on tester GPIO. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT640N | TTL-compatible input thresholds (VIH = 2.0V min), otherwise identical pinout and AC specs. | Preferred in mixed 5V TTL/CMOS systems where SN74HC640DW's CMOS thresholds may cause marginal noise immunity. | Select SN74HCT640N when interfacing directly to legacy 74LS logic without level shifters. |
| 74LCX640M | Lower VCC range (2.0V–3.6V), higher speed (tpd = 5.5ns @ 3.3V), and 3.6V-tolerant I/O. | Optimized for 3.3V-only systems with tighter timing budgets; not suitable for 5V operation. | Choose 74LCX640M only for new 3.3V designs requiring sub-6ns latency and lower power than HC family. |
Compared with SN74HC640DW, SN74HCT640N offers better noise margin in 5V TTL environments but sacrifices universal 2V–6V flexibility, while 74LCX640M delivers superior speed and 3.3V efficiency at the cost of 5V incompatibility - making SN74HC640DW the optimal choice for broad-voltage industrial backplanes.
Availability
SN74HC640DW is available at Aetrix Electronics and suitable for industrial backplane interfaces, legacy microprocessor bus extensions, test equipment data acquisition buses, and automated test fixture control requiring stable component supply across extended product lifecycles.
Supply support for SN74HC640DW 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 delivering analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74HC640DW belongs to TI's 74HC logic family - engineered for robust, low-power, wide-supply-range digital interfacing in harsh industrial environments where reliability and voltage flexibility are critical.
FAQ
What is the maximum clock frequency supported by SN74HC640DW in a data bus application?
The SN74HC640DW does not operate on a clock signal - it is an asynchronous transceiver. Its usable data rate is determined by propagation delay (tpd = 8ns typical at 6V) and system timing margins. For reliable operation with setup/hold requirements, it supports bus cycle rates up to approximately 12.5 MHz in well-designed layouts with matched trace lengths and proper termination.
Does SN74HC640DW require external pull-up resistors on DIR or OE pins?
No, SN74HC640DW does not require external pull-up resistors on DIR or OE. Its input current is limited to ±1 µA max, and internal design ensures stable logic states with direct MCU GPIO connection. However, floating inputs must be avoided - tie unused control pins to VCC or GND per TI SCBA004 guidelines to prevent undefined operation.
Can SN74HC640DW safely interface a 5V microcontroller bus with a 3.3V peripheral bus?
SN74HC640DW can translate between 5V and 3.3V logic levels only if operated at VCC = 3.3V. At 3.3V supply, its VOH is ≥3.15V (VIH = 2.31V min for 3.3V peripherals) and VOL is ≤0.26V - meeting 3.3V interface requirements. Driving a 5V bus requires level-shifting circuitry, as SN74HC640DW outputs are not 5V-tolerant when VCC = 3.3V.
What is the thermal resistance (RθJA) of SN74HC640DW in its SOIC package?
The junction-to-ambient thermal resistance (RθJA) for SN74HC640DW in the DW (SOIC-20) package is 58°C/W, as specified in the Thermal Information table. This value assumes standard JEDEC 2-layer board conditions; actual performance improves with copper pour and thermal vias beneath the package.
Is SN74HC640DW pin-compatible with SN74LS640 or other 74LS-series transceivers?
No, SN74HC640DW is not pin-compatible with SN74LS640. While both are octal transceivers with 3-state outputs, SN74LS640 uses a 24-pin package and different pin assignments (e.g., separate A/B enable lines). SN74HC640DW's 20-pin SOIC layout and shared DIR/OE control differ fundamentally from LS-series implementations - direct replacement requires PCB redesign.
SN74HC640DW 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, 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
SN74HC640DW FAQ
1.How can I place an order for SN74HC640DW through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74HC640DW 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 SN74HC640DW reliable?
The price and inventory of SN74HC640DW are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74HC640DW is usually 5 days.
3.What payment methods are accepted for SN74HC640DW?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74HC640DW transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74HC640DW?
SN74HC640DW orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74HC640DW 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 SN74HC640DW?
For technical support, including SN74HC640DW datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74HC640DW requirements.
6.How does Aetrix verify that SN74HC640DW is sourced from the original manufacturer or authorized distributors?
All SN74HC640DW 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 SN74HC640DW meets industry standards.
7.What is the process for return or replacement of SN74HC640DW?
All SN74HC640DW units undergo pre-shipment inspection (PSI). If there is an issue with SN74HC640DW, 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 SN74HC640DW part is unused and in its original packaging.
Return procedure for SN74HC640DW:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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