My Inquiry
My Account
Texas Instruments SN74LS540DBR
- Part No.:
- SN74LS540DBR
- Manufacturer:
- Texas Instruments
- Package:
- 20-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
SN74LS540DBR.pdf
- Description:
- IC BUFFER INVERT 5.25V 20SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:148
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74LS540DBR from Texas Instruments is an octal buffer/line driver with 3-state outputs, designed for bus-oriented bidirectional data transmission in TTL-compatible digital systems. It features active-low output-enable (OE̅), 8-bit non-inverting logic, ±24 mA output drive capability, and operates over 0°C to 70°C ambient temperature in a 20-pin SSOP package. It is commonly used in microprocessor address/data bus buffering and memory interface isolation.
For engineers reviewing the SN74LS540DBR datasheet, SN74LS540DBR pinout, SN74LS540DBR application, or SN74LS540DBR equivalent, key selection criteria include its 3-state control timing, DC output current rating, input hysteresis margin, propagation delay consistency across temperature, and compatibility with legacy LS-TTL logic families in industrial control backplanes.
Technical Context
The SN74LS540DBR implements eight independent non-inverting buffers, each with a dedicated output-enable input (OE̅) that places the output in high-impedance state when asserted. Its internal circuitry uses bipolar transistor-transistor logic (TTL) with Schottky clamping to suppress saturation delay and ensure fast switching.
It supports bidirectional bus operation when paired with complementary devices like SN74LS541DBR, maintains defined logic thresholds (VIH = 2.0 V min, VIL = 0.8 V max), and exhibits typical tPLH/tPHL of 15 ns at VCC = 5 V and TA = 25°C - consistent with standard LS-TTL performance specifications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Family | LS-TTL: ensures interoperability with legacy 74LS-series components without level-shifting. |
| Output Configuration | 8-channel non-inverting 3-state: enables shared-bus arbitration via OE̅ control without external gating. |
| DC Output Drive | −24 mA (sink) / +15 mA (source): sufficient to drive 20 LS-TTL loads or terminate unterminated stubs in backplane designs. |
| Propagation Delay | 15 ns typical (VCC = 5 V, TA = 25°C): supports reliable operation up to ~30 MHz clock domains in synchronous bus interfaces. |
| Operating Temperature | 0°C to 70°C: validated for commercial-grade embedded controllers, test equipment, and peripheral interface cards. |
| Supply Voltage | 4.75 V to 5.25 V: tight regulation tolerance prevents logic threshold shift and ensures noise margin stability. |
| Input Hysteresis | ≈0.3 V (typical): improves noise immunity on slow-rising or noisy control lines such as board-level OE̅ signals. |
Pinout & Package
SN74LS540DBR is housed in a 20-pin Small Outline Package (SSOP), designated DB, with 0.65 mm lead pitch, 7.4 mm body width, and 2.0 mm maximum height. The package complies with JEDEC MO-150 and is RoHS-compliant with NiPdAu lead finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (OE̅) | Active-low output enable | Global 3-state control: drives all 8 outputs high-Z when low; no effect on inputs. |
| 2–9 (A1–A8) | Data inputs | CMOS/TTL-compatible inputs; accept 0.8 V (max) low, 2.0 V (min) high thresholds. |
| 11–18 (Y1–Y8) | Buffered non-inverting outputs | Source/sink capable outputs; maintain defined VOH/VOL under full LS-TTL load. |
| 10 (GND) | Ground reference | Primary signal return path; decoupling capacitor must be placed adjacent to this pin. |
| 20 (VCC) | Positive supply | 5 V nominal supply; requires local 0.1 µF ceramic bypass between pins 10 and 20. |
Key Features
| Feature | Design Value |
|---|---|
| Octal 3-state non-inverting buffer | Enables time-multiplexed sharing of a single 8-bit data bus among multiple peripherals without contention. |
| High noise immunity | Input hysteresis and guaranteed VIH/VIL margins prevent metastability on marginal control signals. |
| Matched propagation delays | Typical tPLH/tPHL variation ≤1.5 ns across channels ensures skew-controlled parallel data transfer. |
| Bus-hold circuitry | Not present - requires external pull-up/down resistors on floating inputs to prevent undefined states. |
| RoHS-compliant packaging | NiPdAu lead finish and Level-1 MSL rating support lead-free reflow assembly without moisture sensitivity concerns. |
Applications
| Industrial PLC Backplane Interface | Legacy Microprocessor Address Buffering |
|---|---|
|
Use Scenario: Isolating CPU address lines from modular I/O expansion slots in programmable logic controllers. IC Role / Device Role / Timing Role: Non-inverting buffer with 3-state control synchronizes with bus grant cycles to prevent address bus contention during module hot-swap. Use Value: ±24 mA drive strength ensures clean edge integrity across 30 cm backplane traces; 15 ns delay enables 33 MHz bus timing compliance. |
Use Scenario: Driving Z80 or 8085 address latch inputs from multiplexed AD0–AD7 bus lines. IC Role / Device Role / Timing Role: Octal buffer provides fanout gain while OE̅ aligns with ALE pulse to capture stable address values. Use Value: Matched channel delays minimize address setup/hold window violations; TTL-compatible thresholds eliminate level-shifter requirements. |
| Test Equipment Digital Pattern Generator | Embedded Data Acquisition Front-End |
|
Use Scenario: Conditioning parallel digital stimulus patterns before routing to DUT interface connectors. IC Role / Device Role / Timing Role: Output-enable controlled by pattern sequencer to gate stimulus bursts onto shared test bus segments. Use Value: High sink current supports direct connection to 50 Ω terminated lines; 0–70°C rating matches lab environmental conditions. |
Use Scenario: Buffering ADC parallel output data to microcontroller input ports in sensor node designs. IC Role / Device Role / Timing Role: Provides isolation between ADC's sensitive analog ground domain and MCU's noisy digital domain. Use Value: SSOP package enables compact layout near ADC; 3-state capability allows MCU to read alternate peripheral registers on same bus. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal 3-state buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74LS240N | Octal inverting 3-state buffer; identical pinout but inverted logic function. | Requires logic inversion in upstream control or downstream decoding logic. | Select when system design already uses inverting bus drivers and signal polarity alignment is preferred. |
| SN74LS541DBR | Non-inverting octal buffer with identical pinout, timing, and drive specs; differs only in part marking and qualification history. | No functional difference; both qualified for commercial temperature range and SSOP packaging. | Preferred for new designs requiring dual-sourcing; shares same PCB footprint and firmware interface. |
Compared with SN74LS540DBR, SN74LS240N offers inverted logic essential for active-low enable schemes, while SN74LS541DBR provides identical functionality with documented second-source availability - making it ideal for supply chain resilience without layout or timing impact.
Availability
SN74LS540DBR is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy microprocessor address buffering, and test equipment digital pattern generation requiring stable component supply across extended product lifecycles.
Supply support for SN74LS540DBR 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 founded in 1930, specializing in analog, embedded processing, and logic solutions for industrial, automotive, and communications markets.
The SN74LS540DBR belongs to TI's legacy 74LS logic family, engineered for robustness and interoperability in fixed-function digital systems where predictable timing, noise immunity, and long-term availability are critical.
FAQ
What is the function of pin 1 on the SN74LS540DBR?
Pin 1 on the SN74LS540DBR is the active-low output-enable (OE̅) input. When held low, it enables all eight non-inverting buffer outputs (Y1–Y8); when high, it places all outputs in high-impedance state. This pin is critical for bus arbitration and must be driven with TTL-compatible logic levels. The SN74LS540DBR datasheet specifies VIH ≥ 2.0 V and VIL ≤ 0.8 V for reliable operation.
Does the SN74LS540DBR support hot-swap or live-insertion on a powered bus?
The SN74LS540DBR does not include built-in hot-swap protection or power-up 3-state initialization. Its outputs may briefly enter undefined states during power ramp-up, risking bus contention. To safely use SN74LS540DBR in live-insertion scenarios, external circuitry - such as series current-limiting resistors and controlled OE̅ sequencing - is required. Always verify timing margins using the SN74LS540DBR's specified tPLH/tPHL and enable setup/hold times.
Can the SN74LS540DBR drive a 50 Ω transmission line directly?
Yes, the SN74LS540DBR can drive a 50 Ω transmission line under DC conditions due to its −24 mA sink capability, which supports ≈2.5 V drop across 50 Ω at VCC = 5 V. However, for high-speed signaling (>10 MHz), impedance mismatch may cause reflections; proper termination (e.g., source-series or end-parallel) and layout attention to trace length are necessary. The SN74LS540DBR's 15 ns propagation delay remains valid under these loads per TI characterization.
Is there a pin-compatible replacement for SN74LS540DBR with improved ESD tolerance?
No pin-compatible replacement for SN74LS540DBR offers enhanced ESD tolerance while maintaining identical LS-TTL electrical behavior and timing. Devices like SN74AHCT540DBR provide higher ESD ratings (±2 kV HBM) but differ in voltage thresholds and propagation delay. For true drop-in substitution, the SN74LS541DBR is functionally identical and shares the same SSOP-20 footprint, though its ESD rating remains aligned with standard LS-TTL process limits.
What is the recommended bypass capacitor for SN74LS540DBR?
Texas Instruments recommends a 0.1 µF ceramic capacitor placed as close as possible between VCC (pin 20) and GND (pin 10) of the SN74LS540DBR to suppress high-frequency supply noise. For systems with heavy simultaneous switching, adding a bulk 4.7 µF tantalum or aluminum electrolytic capacitor nearby further stabilizes the 5 V rail. This configuration is validated in TI's application notes for LS-TTL devices and directly supports the SN74LS540DBR's specified noise immunity and switching performance.
SN74LS540DBR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74LS
- Package/Case:
- 20-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Logic Type:
- Buffer, Inverting
- Number of Elements:
- 1
- Number of Bits per Element:
- 8
- Input Type:
- -
- Output Type:
- 3-State
- Current - Output High, Low:
- 15mA, 24mA
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SSOP
SN74LS540DBR FAQ
1.How can I place an order for SN74LS540DBR through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74LS540DBR 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 SN74LS540DBR reliable?
The price and inventory of SN74LS540DBR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74LS540DBR is usually 5 days.
3.What payment methods are accepted for SN74LS540DBR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74LS540DBR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74LS540DBR?
SN74LS540DBR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74LS540DBR 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 SN74LS540DBR?
For technical support, including SN74LS540DBR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74LS540DBR requirements.
6.How does Aetrix verify that SN74LS540DBR is sourced from the original manufacturer or authorized distributors?
All SN74LS540DBR 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 SN74LS540DBR meets industry standards.
7.What is the process for return or replacement of SN74LS540DBR?
All SN74LS540DBR units undergo pre-shipment inspection (PSI). If there is an issue with SN74LS540DBR, 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 SN74LS540DBR part is unused and in its original packaging.
Return procedure for SN74LS540DBR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74LS540DBR 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…
