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onsemi MC74HCT245ADT
- Part No.:
- MC74HCT245ADT
- Manufacturer:
- onsemi
- Package:
- 20-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
MC74HCT245ADT.pdf
- Description:
- IC TXRX NON-INVERT 5.5V 20TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,171
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Product details
Overview
MC74HCT245ADT from onsemi is an octal 3-state noninverting bus transceiver with LSTTL-compatible inputs, designed for bidirectional asynchronous data bus interfacing between TTL/NMOS and CMOS systems. It operates from 4.5 V to 5.5 V, supports ±35 mA output drive per pin, features active-low Output Enable and unidirectional Direction control, and is used in industrial control backplanes and legacy system bus bridging.
For engineers reviewing the MC74HCT245ADT datasheet, pinout, applications, or equivalent options, key selection considerations include its TSSOP-20 package, 22 ns (min) A↔B propagation delay at 5 V, 3-state leakage ≤±10 µA at 125 °C, and compatibility with LS245 pinout for drop-in replacement in legacy designs.
Technical Context
The MC74HCT245ADT implements a dual-bus transceiver architecture with independent A and B 8-bit I/O ports, controlled by a single Direction input that determines data flow direction (A→B or B→A), and an active-low Output Enable that places both ports in high-impedance state. Its silicon-gate CMOS process ensures LSTTL-compatible input thresholds (VIH = 2.0 V, VIL = 0.8 V) while driving 15 LSTTL loads.
It complies with JEDEC Standard No. 7A, supports operation from –55 °C to +125 °C, and integrates 76 equivalent gates. Input leakage is limited to ±1.0 µA at 5.5 V, and three-state I/O capacitance is 15 pF - critical for minimizing bus loading in high-speed digital backplanes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Voltage | 4.5 V to 5.5 V - ensures stable operation across industrial-grade 5 V rails with ±10% tolerance. |
| Propagation Delay (A↔B) | 22 ns (–55 to 25 °C) - enables reliable timing in 20 MHz+ synchronous bus environments. |
| Output Drive | ±35 mA per pin - sufficient to directly drive 15 LSTTL loads without external buffers. |
| Input Thresholds | VIH = 2.0 V, VIL = 0.8 V - guarantees interoperability with standard TTL and NMOS logic outputs. |
| Three-State Leakage | ±10 µA max at 125 °C - maintains signal integrity during high-impedance isolation in hot industrial enclosures. |
| I/O Capacitance | 15 pF in high-Z state - minimizes capacitive loading on shared data buses, preserving edge rates. |
| Operating Temperature | –55 °C to +125 °C - qualified for under-hood automotive, industrial PLC, and aerospace avionics applications. |
Pinout & Package
TSSOP-20 wide-body package (Case 948E), 6.5 mm × 4.4 mm footprint, 0.65 mm pitch, Pb-free and RoHS compliant.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Output Enable (active-low) | Asserting low enables A/B port drivers; high forces all I/O into high-impedance state for bus sharing. |
| 2–9 | A-port inputs/outputs | Bi-directional data lines A1–A8; direction determined by Pin 19; electrically identical to B-port pins. |
| 10 | GND | Ground reference for all internal circuitry and I/O; must be low-impedance connection to minimize noise coupling. |
| 11–18 | B-port inputs/outputs | Bi-directional data lines B1–B8; functionally mirrored to A-port with direction controlled by Pin 19. |
| 19 | Direction control | High = A→B data flow; Low = B→A data flow; defines signal path polarity for full-duplex bus arbitration. |
| 20 | VCC | Positive supply rail (4.5–5.5 V); decoupling capacitor (0.1 µF ceramic) required within 5 mm of this pin. |
Key Features
| Feature | Design Value |
|---|---|
| LSTTL-compatible inputs | VIH = 2.0 V / VIL = 0.8 V thresholds enable direct interface to legacy 74LS logic without level-shifting circuitry. |
| 3-state bus isolation | Active-high Z-state control via OE# allows multiple transceivers to share a common data bus without contention. |
| LS245 pinout compatibility | Identical pin assignment to 74LS245 - enables drop-in replacement in existing PCB layouts with no redesign. |
| High noise immunity | Input hysteresis and 400 mV noise margin at VCC = 5 V ensure robust operation in electrically noisy industrial environments. |
| Pb-free & RoHS compliant | Meets EU Directive 2011/65/EU; suitable for green manufacturing and export to regulated markets without exemptions. |
Applications
| Industrial Backplane Interfacing | Legacy System Bus Bridging |
|---|---|
|
Use Scenario: Connecting microcontroller local bus to a multi-slot ISA-style backplane carrying legacy peripherals. IC Role / Device Role / Timing Role: Bidirectional data buffer isolating CPU address/data bus from backplane capacitance and noise. Use Value: Enables 8-bit parallel communication at up to 20 MHz while preventing bus contention during DMA cycles via OE# control. |
Use Scenario: Integrating modern FPGA-based controllers into aging test equipment using 74LS-based logic subsystems. IC Role / Device Role / Timing Role: Level-translating transceiver matching LS245 pinout to bridge 3.3 V/5 V domain boundaries. Use Value: Eliminates need for discrete resistor networks or dedicated level shifters, reducing BOM count and layout area. |
| Automotive ECU Diagnostics Interface | Programmable Logic Controller I/O Expansion |
|
Use Scenario: Isolating diagnostic CAN controller data lines from high-noise engine control module power domains. IC Role / Device Role / Timing Role: Controlled-direction data gate managing bi-directional J1850/PWM protocol signals between MCU and vehicle bus. Use Value: Provides 125 °C-rated isolation and ±35 mA drive to maintain signal integrity across long harness runs in under-hood environments. |
Use Scenario: Expanding digital I/O capacity of compact PLC modules using daisy-chained parallel bus architecture. IC Role / Device Role / Timing Role: Octal bus repeater enabling modular I/O card stacking with deterministic propagation delay. Use Value: Supports real-time deterministic response (<33 ns max delay) required for motion control loop synchronization. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar bus transceiver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT245PWR | TSSOP-20, same logic function and DC specs; propagation delay 23 ns (vs. 22 ns), IOZ = ±5 µA @ 125 °C (vs. ±10 µA). | TI part optimized for lower leakage in extended-temperature embedded control; slightly higher cost in low-volume procurement. | Select when tighter three-state leakage spec is required for ultra-low-power sleep modes. |
| 74HCT245D,653 | SOIC-20 package (Case 751D); identical AC/DC specs but 1.75 mm taller profile; thermal resistance 125 K/W (vs. 140 K/W for TSSOP). | Better thermal performance in convection-cooled industrial enclosures; incompatible footprint with MC74HCT245ADT's TSSOP-20. | Select when board space permits SOIC and thermal dissipation >150 mW is needed in continuous operation. |
Compared with SN74HCT245PWR and 74HCT245D,653, the MC74HCT245ADT offers the lowest profile (1.2 mm height), best fit for space-constrained TSSOP layouts, and highest guaranteed leakage tolerance - making it optimal for high-density industrial backplanes where mechanical clearance and bus contention margin are critical.
Availability
MC74HCT245ADT is available at Aetrix Electronics and suitable for industrial backplane interfacing, legacy system bus bridging, automotive ECU diagnostics interfaces, and programmable logic controller I/O expansion requiring stable component supply across extended temperature ranges.
Supply support for MC74HCT245ADT 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
onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensors, and logic solutions for automotive, industrial, and cloud infrastructure markets.
The MC74HCT245ADT belongs to onsemi's HCT logic family, engineered for seamless TTL-to-CMOS interfacing in harsh-environment applications where reliability, pin compatibility, and extended temperature operation are mandatory.
FAQ
What is the maximum operating temperature range for the MC74HCT245ADT?
The MC74HCT245ADT is rated for operation from –55 °C to +125 °C, fully qualified for under-hood automotive, industrial control, and aerospace applications where ambient temperatures exceed standard commercial grade limits. This specification is verified per JEDEC JESD22-A108 and confirmed in the onsemi datasheet Rev. 13, page 3.
Does the MC74HCT245ADT support true bidirectional data flow on the same pins?
Yes, the MC74HCT245ADT supports true bidirectional operation: Pins 2–9 (A-port) and 11–18 (B-port) are fully reversible I/Os. Data direction (A→B or B→A) is controlled solely by the Direction input (Pin 19), while Output Enable (Pin 1) independently places both ports in high-impedance state - enabling time-multiplexed bidirectional bus use.
Is the MC74HCT245ADT pin-compatible with the 74LS245?
Yes, the MC74HCT245ADT is explicitly designed as a drop-in replacement for the 74LS245, with identical pinout, function table, and mechanical dimensions in TSSOP-20 (Case 948E). This compatibility is stated in the onsemi datasheet front page and validated in Figure 1 and PIN ASSIGNMENT section.
What is the recommended decoupling for the MC74HCT245ADT?
A 0.1 µF ceramic capacitor placed within 5 mm of Pin 20 (VCC) and connected to Pin 10 (GND) is the minimum recommended decoupling for the MC74HCT245ADT. For systems with high-frequency switching noise, add a 4.7 µF tantalum or polymer capacitor in parallel to suppress low-frequency ripple, as specified in onsemi Application Note AND8003/D.
Can the MC74HCT245ADT operate at 3.3 V supply voltage?
No, the MC74HCT245ADT requires a minimum supply voltage of 4.5 V and is not specified for 3.3 V operation. Its input thresholds (VIH = 2.0 V) and output drive characteristics are optimized for 5 V TTL/CMOS systems. For 3.3 V applications, consider the MC74LCX245 or SN74LVC245A instead.
MC74HCT245ADT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- 74HCT
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- 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:
- -55°C ~ 125°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-TSSOP
MC74HCT245ADT FAQ
1.How can I place an order for MC74HCT245ADT through Aetrix?
Please submit a Request for Quotation (RFQ) for MC74HCT245ADT 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 MC74HCT245ADT reliable?
The price and inventory of MC74HCT245ADT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MC74HCT245ADT is usually 5 days.
3.What payment methods are accepted for MC74HCT245ADT?
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4.How is shipping managed for MC74HCT245ADT?
MC74HCT245ADT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MC74HCT245ADT 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 MC74HCT245ADT?
For technical support, including MC74HCT245ADT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MC74HCT245ADT requirements.
6.How does Aetrix verify that MC74HCT245ADT is sourced from the original manufacturer or authorized distributors?
All MC74HCT245ADT 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 MC74HCT245ADT meets industry standards.
7.What is the process for return or replacement of MC74HCT245ADT?
All MC74HCT245ADT units undergo pre-shipment inspection (PSI). If there is an issue with MC74HCT245ADT, 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 MC74HCT245ADT part is unused and in its original packaging.
Return procedure for MC74HCT245ADT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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