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STMicroelectronics M74HCT540B1R
- Part No.:
- M74HCT540B1R
- Manufacturer:
- STMicroelectronics
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
M74HCT540B1R.pdf
- Description:
- IC BUFFER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:756
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Product details
Overview
M74HCT540B1R from STMicroelectronics is an octal inverting bus buffer with 3-state outputs, designed for bidirectional data bus isolation in TTL- and CMOS-compatible digital systems. It features 12 ns typical propagation delay at 4.5 V, ±6 mA symmetrical output drive, and dual active-low enable inputs (G1, G2) that place all eight outputs in high-impedance state when asserted. Used in address/data bus buffering for microcontroller peripheral interfaces.
For engineers reviewing the M74HCT540B1R datasheet, M74HCT540B1R pinout, M74HCT540B1R application, or M74HCT540B1R equivalent, key selection criteria include guaranteed 3-state timing (tPZL/tPHZ ≤ 41 ns), TTL-compatible input thresholds (VIH ≥ 2.0 V, VIL ≤ 0.8 V), and DIP-20 package compatibility with legacy board layouts.
Technical Context
The device implements a dual-input AND logic gate for 3-state control: both G1 and G2 must be low to enable inverted output buffering; either high forces all Y1–Y8 into high-impedance. Inputs are protected against ESD and transient overvoltage, supporting robust operation in industrial environments.
Its C2MOS silicon gate process delivers balanced tPLH ≅ tPHL propagation delays and symmetrical |IOH| = IOL = 6 mA (min) drive capability, enabling clean signal integrity across bidirectional buses without external termination.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC Range | 4.5 V to 5.5 V - Ensures stable operation under standard 5 V TTL/CMOS rail tolerances. |
| tPD (Typ.) | 12 ns at VCC = 4.5 V, CL = 50 pF - Enables reliable 33 MHz bus operation with margin. |
| IOH / IOL | ±6 mA min - Drives standard TTL loads without fanout limitation or external pull-ups. |
| VIH / VIL | 2.0 V min / 0.8 V max - Guarantees interoperability with 5 V TTL outputs and CMOS inputs. |
| ICC (Max) | 40 µA at TA = 85°C - Supports low-static-power system design in thermally constrained enclosures. |
| CIN | 10 pF max - Minimizes capacitive loading on driving gates, preserving edge rates. |
| tPZL / tPHZ | 41 ns max at VCC = 4.5 V - Defines worst-case bus release timing for multi-master arbitration. |
Pinout & Package
Supplied in plastic DIP-20 (0.300" wide) package with 2.54 mm pitch, optimized for through-hole PCB assembly and legacy socket compatibility.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 19 | G1, G2 | Active-low 3-state enable inputs - Both must be low to activate inverted output buffering. |
| 2–9 | A1–A8 | Inverting data inputs - Each drives corresponding Yn output with polarity inversion. |
| 11–18 | Y1–Y8 | Inverting 3-state bus outputs - High-impedance when G1 or G2 is high; otherwise Yn = NOT(An). |
| 10 | GND | Ground reference - Serves as return path for all input/output currents and internal logic. |
| 20 | VCC | Positive supply - Powers internal logic and output drivers; requires local 0.1 µF decoupling. |
Key Features
| Feature | Design Value |
|---|---|
| Inverting 3-state bus buffer | Provides polarity-inverted data transfer with controlled bus release via dual enable logic. |
| Pin- and function-compatible with 74LS540 | Enables drop-in replacement in existing 74-series designs without layout or firmware changes. |
| Balanced tPLH/tPHL propagation | Ensures minimal duty cycle distortion on clocked or bidirectional data streams. |
| Symmetrical output impedance | Delivers matched rise/fall times and reduces ground bounce during simultaneous switching. |
| Input ESD protection | Withstands ±2 kV HBM per IEC 61000-4-2, reducing need for external TVS on board-level I/O. |
Applications
| Microcontroller Address Bus Isolation | Legacy Peripheral Interface Buffering |
|---|---|
Use Scenario: Isolating 8-bit address lines between an MCU and multiple memory-mapped peripherals sharing a common bus. IC Role / Device Role / Timing Role: Inverting 3-state buffer controlling bus access timing via G1/G2 enables deterministic arbitration and prevents contention. Use Value: Eliminates need for discrete logic or bus transceivers while maintaining strict setup/hold margins due to 12 ns tPD and matched delays. | Use Scenario: Interfacing modern HCMOS controllers with legacy TTL-based display controllers or keypad scanners. IC Role / Device Role / Timing Role: Level-shifting and drive-strengthening buffer ensuring VIH/VIL compliance and 6 mA sink/source capability. Use Value: Achieves reliable communication without external pull-ups or level translators, reducing BOM count and layout complexity. |
| Industrial PLC I/O Expansion Module | Digital Test Equipment Signal Conditioning |
Use Scenario: Buffering parallel I/O signals in modular PLC backplanes where hot-swap and fault isolation are required. IC Role / Device Role / Timing Role: Bidirectional bus isolator with fast disable (tPHZ ≤ 41 ns) enabling safe module insertion/removal under power. Use Value: Prevents bus contention during module reconfiguration, meeting IEC 61000-6-2 immunity requirements via integrated input protection. | Use Scenario: Driving calibrated test loads in automated test equipment requiring precise edge control and repeatable timing. IC Role / Device Role / Timing Role: Precision timing buffer delivering matched tPLH/tPHL and low jitter (<1 ns variation) on buffered clock/data paths. Use Value: Maintains sub-nanosecond skew across 8 channels, critical for synchronized sampling in boundary-scan or JTAG applications. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74HCT540N | Same logic function and AC specs; DIP-20 package; identical pinout and enable architecture. | No difference - fully interchangeable in footprint and timing-critical designs. | Select when sourcing from TI-authorized channels or requiring TI-specific qualification documentation. |
| 74HCT540D | SOP-20 package only; same electrical specs but 1.27 mm pitch limits use in through-hole prototypes. | Requires PCB redesign for surface-mount assembly; unsuitable for breadboard or DIP socket evaluation. | Choose for space-constrained production boards where reflow compatibility is prioritized over prototyping flexibility. |
Compared with SN74HCT540N and 74HCT540D, the M74HCT540B1R uniquely supports legacy DIP-20 through-hole assembly while retaining full functional equivalence and industrial temperature range (−55°C to +125°C), making it optimal for field-deployed equipment requiring long-term mechanical reliability.
Availability
M74HCT540B1R is available at Aetrix Electronics and suitable for microcontroller bus isolation, industrial PLC I/O expansion, and legacy peripheral interface applications requiring stable component supply across extended temperature ranges and long product lifecycles.
Supply support for M74HCT540B1R 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management ICs with vertical manufacturing capabilities.
The M74HCT540B1R belongs to ST's high-speed CMOS logic family, engineered for seamless interoperability between TTL, NMOS, and CMOS systems in harsh-environment industrial control applications.
FAQ
What is the maximum operating temperature range for M74HCT540B1R?
The M74HCT540B1R is rated for operation from −55°C to +125°C, validated per STMicroelectronics' industrial-grade qualification standards. This extended range supports deployment in uncontrolled environments such as outdoor automation cabinets, motor drive enclosures, and transportation infrastructure systems without thermal derating.
Can M74HCT540B1R drive standard TTL loads directly?
Yes - its guaranteed IOL = 6 mA (min) at VOL ≤ 0.4 V and IOH = −6 mA (min) at VOH ≥ 4.1 V meets or exceeds standard TTL fan-out requirements. No external pull-up resistors are needed when interfacing with 74LS or 74F series inputs, simplifying interconnect design.
How does the dual-enable (G1/G2) logic affect bus arbitration?
G1 and G2 form a wired-AND enable: both must be low to activate outputs. This allows hierarchical bus control - e.g., one enable tied to system select, the other to local peripheral ready - preventing unintended bus drive during reset or fault conditions.
Is there a non-inverting version of this device in the same package?
Yes - the M74HCT541B1R is the functionally identical non-inverting octal buffer in the same DIP-20 package, sharing identical pinout, timing, and DC specifications except for output polarity. Pin-for-pin replacement is possible with only logic-level inversion adjustment in firmware or upstream logic.
M74HCT540B1R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- 74HCT
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Logic Type:
- Buffer, 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:
- Through Hole
- Supplier Device Package:
- 20-DIP
M74HCT540B1R FAQ
1.How can I place an order for M74HCT540B1R through Aetrix?
Please submit a Request for Quotation (RFQ) for M74HCT540B1R 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 M74HCT540B1R reliable?
The price and inventory of M74HCT540B1R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M74HCT540B1R is usually 5 days.
3.What payment methods are accepted for M74HCT540B1R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M74HCT540B1R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M74HCT540B1R?
M74HCT540B1R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M74HCT540B1R 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 M74HCT540B1R?
For technical support, including M74HCT540B1R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M74HCT540B1R requirements.
6.How does Aetrix verify that M74HCT540B1R is sourced from the original manufacturer or authorized distributors?
All M74HCT540B1R 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 M74HCT540B1R meets industry standards.
7.What is the process for return or replacement of M74HCT540B1R?
All M74HCT540B1R units undergo pre-shipment inspection (PSI). If there is an issue with M74HCT540B1R, 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 M74HCT540B1R part is unused and in its original packaging.
Return procedure for M74HCT540B1R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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