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onsemi 74VHC245MX
- Part No.:
- 74VHC245MX
- Manufacturer:
- onsemi
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
74VHC245MX.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,552
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Product details
Overview
74VHC245MX from ON Semiconductor is an advanced high-speed CMOS octal bidirectional bus transceiver with 3-STATE outputs, designed for asynchronous data exchange between two 8-bit buses. It features 4.0 ns typical propagation delay at 5 V, ±25 mA output drive capability, and operates across 2.0–5.5 V supply range. Used in microcontroller peripheral interfacing, memory expansion, and legacy bus isolation.
For engineers reviewing the 74VHC245MX datasheet, pinout, applications, or equivalent options, key selection criteria include bidirectional control via T/R input, independent OE-driven 3-STATE isolation, SOIC-20 package compatibility, and VHC-family noise immunity (28% VCC).
Technical Context
The 74VHC245MX implements a dual-bus architecture with separate A-side (A0–A7) and B-side (B0–B7) I/O terminals, where data direction is controlled by the T/R input level and bus isolation is enabled/disabled by the active-low OE input. Its silicon gate CMOS process delivers TTL-compatible speed without bipolar power penalties.
All inputs include ESD protection circuits, and unused I/Os in HIGH-Z state must be externally biased to VCC or GND per design requirements. The device supports mixed-voltage operation only within its specified 2.0–5.5 V VCC range and does not support level-shifting beyond that window.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Propagation Delay (tPD) | 4.0 ns typ @ VCC = 5 V, CL = 15 pF - enables high-speed 8-bit parallel transfers up to ~100 MHz system clock domains |
| Supply Voltage Range | 2.0 V to 5.5 V - supports 3.3 V and 5 V logic systems without level translators |
| Output Drive | ±25 mA per pin - sufficient to drive standard CMOS/TTL loads and short PCB traces |
| Input Noise Immunity | 28% VCC min - reduces susceptibility to ground bounce and crosstalk in dense layouts |
| Off-State Leakage (IOZ) | ±2.5 µA max @ VCC = 5.5 V - ensures robust bus isolation during disable |
| Quiescent Current (ICC) | 40 µA max @ TA = 85°C - enables low-static-power operation in battery-backed subsystems |
Pinout & Package
74VHC245MX is supplied in a 20-lead Small Outline Integrated Circuit (SOIC) package, JEDEC MS-013 compliant, 0.300" wide, with surface-mount footprint and Pb-free finish per JEDEC J-STD-020B.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OE) | Active-Low Output Enable | Drives all A/B outputs into HIGH-Z when high; enables bidirectional flow when low |
| 2 (A0) | Side A I/O Terminal | Bi-directional data path - functions as input or 3-STATE output depending on T/R state |
| 3 (A1) | Side A I/O Terminal | Same behavior as A0; part of 8-bit A-bus interface |
| 4 (A2) | Side A I/O Terminal | Supports full byte-wide data transfer from A to B or B to A |
| 5 (A3) | Side A I/O Terminal | Shared bus node requiring external pull-up/down if left floating during HIGH-Z |
| 6 (A4) | Side A I/O Terminal | Not internally terminated; requires external biasing per datasheet guidance |
| 7 (A5) | Side A I/O Terminal | One of eight symmetric I/Os enabling flexible bus topology reconfiguration |
| 8 (A6) | Side A I/O Terminal | Matches timing characteristics of other A-side pins (tPLH/tPHL matched within 1.5 ns skew) |
| 9 (A7) | Side A I/O Terminal | Final bit of A-bus; identical AC/DC specs to A0–A6 |
| 10 (GND) | Ground Reference | Primary return path for all I/O and supply currents; must be low-impedance |
| 11 (B7) | Side B I/O Terminal | Corresponding B-side terminal to A7; direction determined by T/R input |
| 12 (B6) | Side B I/O Terminal | Matches A6 timing and drive strength; supports synchronous 8-bit handshaking |
| 13 (B5) | Side B I/O Terminal | Used in address/data multiplexing schemes where bus direction changes dynamically |
| 14 (B4) | Side B I/O Terminal | Valid for both input capture and output assertion; no internal latching |
| 15 (B3) | Side B I/O Terminal | Requires same external biasing discipline as A-side when disabled |
| 16 (B2) | Side B I/O Terminal | Part of matched group with <1.5 ns inter-pin skew for clean parallel edge alignment |
| 17 (B1) | Side B I/O Terminal | Functions identically to B0–B7; no functional differentiation across B-side |
| 18 (B0) | Side B I/O Terminal | Lowest-order bit of B-bus; electrically identical to all other B-side pins |
| 19 (T/R) | Transmit/Receive Control | High = A→B data flow; Low = B→A data flow; sampled synchronously with OE |
| 20 (VCC) | Positive Supply | Must be decoupled locally with 0.1 µF ceramic capacitor near pin 20 |
Key Features
| Feature | Design Value |
|---|---|
| High-Speed CMOS Architecture | Delivers 4.0 ns tPD at 5 V while maintaining <40 µA ICC - eliminates need for speed/power trade-offs in compact designs |
| Pin-and-Function Compatibility with 74HC245 | Enables drop-in replacement in existing HC-based layouts without netlist or footprint changes |
| Input Protection Circuits | Integrated ESD protection on all inputs meets >2 kV HBM - reduces need for external TVS diodes in industrial environments |
| Low Dynamic Noise (VOLP = 0.9 V typ) | Minimizes switching-induced ground bounce on shared VCC/GND rails during simultaneous 8-bit transitions |
| Wide Operating Voltage (2.0–5.5 V) | Supports direct interface with both 3.3 V microcontrollers and 5 V legacy peripherals without voltage translation ICs |
Applications
| Microcontroller Peripheral Expansion | Legacy ISA Bus Interface |
|---|---|
Use Scenario: Connecting an 8-bit microcontroller to multiple parallel peripherals (ADCs, DACs, LCD controllers) sharing a common data bus. IC Role / Device Role / Timing Role: Bidirectional data bridge enabling time-multiplexed access to peripherals under MCU software control via OE and T/R. Use Value: Eliminates need for discrete logic or multiple unidirectional buffers; single 74VHC245MX handles full byte-wide read/write cycles with <4 ns timing margin. |
Use Scenario: Interfacing modern low-voltage logic to vintage PC/AT ISA expansion slots operating at 5 V TTL levels. IC Role / Device Role / Timing Role: Level-adapted bus transceiver providing 5 V-tolerant I/O and precise direction control synchronized to ISA address strobes. Use Value: Maintains signal integrity across long ISA backplane traces while supporting hot-swap-safe 3-STATE isolation during configuration cycles. |
| Memory-Mapped I/O Multiplexing | Industrial PLC Backplane Isolation |
Use Scenario: Sharing a single 8-bit data bus between RAM, ROM, and register-mapped I/O devices in embedded controllers. IC Role / Device Role / Timing Role: Directionally gated data conduit controlled by address decode logic driving OE and T/R to select active device. Use Value: Enables deterministic bus arbitration with guaranteed 3-STATE disable timing (tPZH ≤ 10 ns), preventing bus contention during address transitions. |
Use Scenario: Isolating programmable logic controller CPU modules from field I/O modules across noisy industrial backplanes. IC Role / Device Role / Timing Role: Galvanically isolated (via optocoupler-driven OE/T/R) bidirectional data repeater ensuring noise-immune communication. Use Value: Provides 28% VCC noise margin and <2.5 µA off-state leakage - critical for reliable operation in 2 kV EFT-prone factory environments. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal bidirectional transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 74HC245D,653 (Nexperia) | Slower tPD (8 ns typ @ 5 V), higher ICC (160 µA max), same SOIC-20 footprint | Less suitable for >25 MHz bus clocks; acceptable for static or low-frequency I/O expansion | Select when cost sensitivity outweighs speed requirement and HC-family familiarity is preferred. |
| SN74LVC245APWR (TI) | Wider VCC range (1.65–3.6 V), lower VOH (≥ VCC − 0.2 V), not 5 V tolerant on I/O | Restricted to 3.3 V-only systems; requires external level shifters for 5 V interfaces | Choose for ultra-low-voltage portable designs where 5 V compatibility is unnecessary. |
Compared with 74HC245D and SN74LVC245APWR, the 74VHC245MX uniquely balances 5 V tolerance, sub-5 ns speed, and <40 µA quiescent current - making it optimal for mixed-voltage industrial controllers needing both legacy compatibility and low standby power.
Availability
74VHC245MX is available at Aetrix Electronics and suitable for microcontroller peripheral expansion, legacy ISA bus interface, and memory-mapped I/O multiplexing requiring stable component supply across extended product lifecycles.
Supply support for 74VHC245MX 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
ON Semiconductor is a global semiconductor manufacturer specializing in energy-efficient power management, analog, logic, and sensor solutions for automotive, industrial, and cloud infrastructure markets.
The 74VHC245MX belongs to ON Semiconductor's legacy logic portfolio, engineered for high-reliability, pin-compatible upgrades of 74HC/74LS families in industrial control, test equipment, and retro-computing applications.
FAQ
What is the maximum operating frequency supported by the 74VHC245MX?
The 74VHC245MX does not specify a maximum clock frequency directly, but its 4.0 ns typical propagation delay at 5 V implies reliable operation in systems with bus cycle times ≥ 8 ns (i.e., up to ~125 MHz theoretical toggle rate). Real-world maximum frequency depends on load capacitance, PCB routing, and supply stability - validated designs typically operate up to 50 MHz with 15 pF loads. Always verify timing margins using worst-case tPLH/tPHL values from the 74VHC245MX datasheet.
Can the 74VHC245MX operate at 3.3 V while interfacing with 5 V logic?
No - the 74VHC245MX is not 5 V tolerant on inputs or outputs when operated at 3.3 V. Its absolute maximum input voltage is 7.0 V, but DC input voltage limits are 0–VCC, meaning 5 V signals applied to T/R, OE, or I/O pins at VCC = 3.3 V exceed the recommended 0–3.3 V range and risk damage or undefined behavior. For mixed-voltage use, operate the 74VHC245MX at 5 V or select a true 5 V-tolerant device like the 74LVT245.
Is the 74VHC245MX pin-compatible with the 74HC245?
Yes - the 74VHC245MX is explicitly stated as pin-and-function compatible with the 74HC245 in its official datasheet. Both share identical SOIC-20 pinout, truth table, and logic behavior. However, the 74VHC245MX offers faster propagation delay (4.0 ns vs. 8 ns typ), lower quiescent current (<40 µA vs. ~160 µA), and improved noise immunity - making it a performance-enhancing drop-in upgrade where layout and BOM changes are prohibited.
What is the purpose of the T/R and OE inputs on the 74VHC245MX?
The T/R (Transmit/Receive) input controls data direction: T/R = LOW enables data flow from B-side to A-side; T/R = HIGH enables A-side to B-side. The OE (Output Enable) input is active-low and globally disables all outputs into HIGH-Z state regardless of T/R state - providing complete bus isolation. Both inputs must be driven to valid logic levels; floating inputs are prohibited per datasheet guidelines.
Does the 74VHC245MX require external pull-up or pull-down resistors on unused I/O pins?
Yes - any unused A0–A7 or B0–B7 terminals during HIGH-Z state must be externally held HIGH or LOW per the 74VHC245MX datasheet. Floating I/Os can cause increased ICC, erratic behavior, or latch-up due to internal input structure sensitivity. Typical practice uses 10 kΩ pull-up to VCC or pull-down to GND, selected based on system default bus state requirements.
74VHC245MX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74VHC
- Package/Case:
- 20-SOIC (0.295", 7.50mm 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:
- 8mA, 8mA
- Voltage - Supply:
- 2V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SOIC
74VHC245MX FAQ
1.How can I place an order for 74VHC245MX through Aetrix?
Please submit a Request for Quotation (RFQ) for 74VHC245MX 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 74VHC245MX reliable?
The price and inventory of 74VHC245MX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 74VHC245MX is usually 5 days.
3.What payment methods are accepted for 74VHC245MX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 74VHC245MX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for 74VHC245MX?
74VHC245MX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your 74VHC245MX 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 74VHC245MX?
For technical support, including 74VHC245MX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 74VHC245MX requirements.
6.How does Aetrix verify that 74VHC245MX is sourced from the original manufacturer or authorized distributors?
All 74VHC245MX 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 74VHC245MX meets industry standards.
7.What is the process for return or replacement of 74VHC245MX?
All 74VHC245MX units undergo pre-shipment inspection (PSI). If there is an issue with 74VHC245MX, 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 74VHC245MX part is unused and in its original packaging.
Return procedure for 74VHC245MX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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