My Inquiry
My Account
Texas Instruments SN74ALS540N
- Part No.:
- SN74ALS540N
- Manufacturer:
- Texas Instruments
- Package:
- 20-DIP (0.300", 7.62mm)
- Datasheet:
-
SN74ALS540N.pdf
- Description:
- IC BUFFER INVERT 5.5V 20DIP
- Quantity:
- Payment:
- Shipping:
Inventory:133
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
SN74ALS540N from Texas Instruments is an octal inverting buffer/line driver with 3-state outputs, designed for bus interfacing and memory address register buffering in TTL-compatible digital systems. It features dual 3-state enable inputs (OE1/OE2), pnp input structure for reduced DC loading, data flowthrough pinout (inputs and outputs on opposite package sides), and operates at 4.5–5.5 V supply. It delivers 12 mA low-level output current and supports propagation delays as low as 2 ns (tPHL) under load.
For engineers reviewing the SN74ALS540N datasheet, SN74ALS540N pinout, SN74ALS540N application, or SN74ALS540N equivalent, key selection criteria include its inverted logic function, dual-NOR 3-state control architecture, PDIP-20 package compatibility, −1.2 V input clamp voltage (VIK), and guaranteed 24 mA IOL capability at VCC = 4.5 V - critical for legacy bus driving and industrial control backplane designs.
Technical Context
The SN74ALS540N implements an octal inverting buffer with independent true/inverted output logic paths per channel, where each output is controlled by a 2-input NOR gate formed by OE1 and OE2 - either high disables all eight outputs into high-impedance state. Its pnp-based input stage reduces DC loading on preceding logic, improving fanout in dense TTL systems.
It uses a data flowthrough pinout: all eight inputs (A1–A8) are on one side of the 20-pin PDIP package, while all eight outputs (Y1–Y8), power (VCC), ground (GND), and enables (OE1/OE2) occupy the opposite side - simplifying PCB routing for bidirectional bus interfaces and minimizing trace crossovers.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Logic Function | Inverting octal buffer with 3-state outputs - provides signal inversion and bus isolation simultaneously |
| Supply Voltage Range | 4.5 V to 5.5 V - compatible with standard 5 V TTL systems and tolerant of nominal rail variation |
| Output Drive (IOL) | 24 mA at VCC = 4.5 V - sufficient to drive multiple TTL loads or terminated transmission lines |
| Propagation Delay (tPHL) | 2 ns minimum, 9 ns maximum at VCC = 4.5–5.5 V, CL = 50 pF - enables high-speed address/data latching |
| Input Clamp Voltage (VIK) | −1.2 V at II = −18 mA - protects against negative transients and ensures robust noise immunity |
| 3-State Enable Logic | 2-input NOR (OE1, OE2) - either enable high forces all Y outputs into high-Z, supporting shared-bus arbitration |
| Quiescent Current (ICC) | 11–19 mA when outputs disabled - predictable power budgeting during bus idle states |
Pinout & Package
SN74ALS540N is housed in a 20-pin plastic dual in-line package (PDIP-N), 0.300″ wide, with standard through-hole mounting and RoHS-compliant NiPdAu lead finish. Thermal impedance θJA is 69°C/W, suitable for natural-convection operation in industrial enclosures.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2, 3, 4, 5, 6, 7, 8 | A1–A8 (Inputs) | Inverting data inputs - accept TTL-level signals; pnp structure minimizes DC loading on source |
| 9 | GND | Ground reference for logic and output stages - must be low-impedance connection for noise control |
| 10 | Y1 | Inverted output corresponding to A1 - drives bus line or memory register with 24 mA sink capability |
| 11–17 | Y2–Y8 | Inverted outputs for A2–A8 - identical electrical behavior; collectively support octal parallel data paths |
| 18 | VCC | Positive supply (4.5–5.5 V) - requires local 0.1 µF ceramic decoupling adjacent to pin |
| 19 | OE1 | Output-enable 1 - active-high input; OR'd with OE2 via internal NOR to control 3-state mode |
| 20 | OE2 | Output-enable 2 - active-high input; dual-enable architecture allows flexible bus arbitration schemes |
Key Features
| Feature | Design Value |
|---|---|
| Data flowthrough pinout | Inputs (A1–A8) on left side, outputs (Y1–Y8) + controls on right - eliminates layer jumps and reduces PCB trace length by >40% in bus layouts |
| pnp input structure | Reduces input current to ≤0.2 mA (IIL) - increases fanout to ≥20 LS-TTL loads without external buffering |
| Dual 3-state enable (OE1/OE2) | NOR-gated control allows independent bus segment enabling or fault-isolation via either enable line |
| Inverting logic function | Yn = NOT(An) - directly supports complemented address/data paths required in many legacy memory controllers |
| Robust input clamping | VIK = −1.2 V - suppresses negative ringing from long traces or inductive switching, preventing false triggering |
Applications
| Industrial PLC Backplanes | Legacy Memory Address Buffering |
|---|---|
Use Scenario: Driving multiplexed address buses between CPU and multiple memory modules in programmable logic controllers. IC Role / Device Role / Timing Role: Octal inverting buffer isolating and strengthening address signals while maintaining timing integrity across 20+ inch backplane traces. Use Value: 24 mA IOL and 9 ns max tPHL ensure setup/hold compliance at 12 MHz clock rates; pnp inputs prevent loading-induced skew across parallel address lines. |
Use Scenario: Interfacing Z80 or 8085 microprocessors to static RAM banks requiring inverted address strobes. IC Role / Device Role / Timing Role: Inverting buffer generating complementary A0–A7 signals for RAM chip-select decoding and address latching. Use Value: Guaranteed −1.2 V VIK clamps negative transients from bus contention, eliminating need for external Schottky clamps and reducing BOM count. |
| Test Equipment Signal Conditioning | TTL-Level Bus Isolation |
Use Scenario: Level-shifting and isolating DUT interface signals in automated test fixtures handling mixed-voltage boards. IC Role / Device Role / Timing Role: 3-state buffer enabling/disabling signal paths between tester channels and device-under-test without signal contention. Use Value: Dual OE inputs allow synchronized enable/disable across multiple SN74ALS540N devices, ensuring glitch-free bus handoff during test sequence transitions. |
Use Scenario: Segregating noisy peripheral buses (e.g., printer port, ISA expansion) from core system logic in embedded instrumentation. IC Role / Device Role / Timing Role: Bidirectional bus driver providing galvanic isolation via high-Z state and controlled edge rates. Use Value: 69°C/W θJA and 19 mA max ICC support continuous operation in sealed enclosures up to 70°C ambient without forced cooling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar octal inverting 3-state buffer applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SN74ALS540-1N | Rated for 48 mA IOL (vs. 24 mA) at VCC = 4.75–5.25 V; otherwise identical pinout, logic, and timing | Required for driving heavier loads (e.g., unterminated 50 Ω lines or >40 TTL units) | Select SN74ALS540-1N only if sustained 48 mA sink capability is verified necessary; SN74ALS540N suffices for standard TTL bus loading. |
| SN74LS240N | Non-inverting octal buffer; lacks pnp inputs (higher IIL ≈ −0.4 mA); 15 mA IOL; slower tPHL (15 ns max) | Suitable for non-inverting paths but requires redesign for polarity-sensitive interfaces like address complementing | Choose SN74LS240N only when inversion is not required and lower speed is acceptable; SN74ALS540N offers superior speed, drive, and input loading. |
Compared with SN74ALS540-1N, the SN74ALS540N trades peak drive strength for broader VCC tolerance (4.5–5.5 V vs. 4.75–5.25 V) and lower thermal stress; versus SN74LS240N, it delivers 3× faster propagation, 60% higher drive, and 50% lower input current - making it optimal for timing-critical, high-fanout legacy systems.
Availability
SN74ALS540N is available at Aetrix Electronics and suitable for industrial PLC backplanes, legacy memory address buffering, and TTL-level bus isolation requiring stable component supply across extended product lifecycles.
Supply support for SN74ALS540N 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 with deep heritage in TTL and advanced logic families.
The SN74ALS540N belongs to TI's ALS (Advanced Low-Power Schottky) logic family, engineered for high-speed, low-power operation in industrial control, test equipment, and military-grade computing systems requiring reliability across temperature extremes.
FAQ
What logic function does the SN74ALS540N implement?
The SN74ALS540N implements an octal inverting buffer with 3-state outputs: each output Yn equals NOT(An), and all outputs enter high-impedance state when either OE1 or OE2 is high. This function is confirmed in the SDAS025D datasheet section "description" and logic diagram. The SN74ALS540N is distinct from the non-inverting SN74ALS541N and cannot substitute without logic inversion in the signal path.
Does the SN74ALS540N support 3.3 V operation?
No, the SN74ALS540N does not support 3.3 V operation. Its recommended operating supply range is strictly 4.5 V to 5.5 V, with absolute maximum VCC at 7 V. Operation below 4.5 V risks undefined output states and degraded noise margins, as specified in the "recommended operating conditions" table of the SDAS025D datasheet. For 3.3 V systems, consider modern alternatives like SN74LVC244A.
What is the purpose of the pnp input structure in the SN74ALS540N?
The pnp input structure in the SN74ALS540N reduces DC input loading: it limits low-level input current (IIL) to −0.2 mA maximum, compared to −0.4 mA in standard LS devices. This allows the SN74ALS540N to drive more downstream TTL loads without signal degradation. The feature is explicitly stated in the datasheet description and contributes directly to its fanout advantage in dense bus architectures.
How are the 3-state outputs controlled on the SN74ALS540N?
The SN74ALS540N uses a 2-input NOR gate for 3-state control: if either OE1 or OE2 is high, all eight outputs (Y1–Y8) go to high-impedance state. Both enables must be low for normal inverted output operation. This architecture is detailed in the "description" section and logic diagram of SDAS025D, enabling flexible bus arbitration using either enable line independently.
Is the SN74ALS540N pin-compatible with the SN74LS240N?
Yes, the SN74ALS540N and SN74LS240N share identical 20-pin PDIP (N) packaging and pin assignments (A1–A8, Y1–Y8, OE1, OE2, GND, VCC), but differ functionally: SN74ALS540N is inverting while SN74LS240N is non-inverting. Substitution requires logic inversion elsewhere in the design and verification of timing margins due to differing propagation delays and drive strengths.
SN74ALS540N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- 74ALS
- Package/Case:
- 20-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- 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:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 20-PDIP
SN74ALS540N FAQ
1.How can I place an order for SN74ALS540N through Aetrix?
Please submit a Request for Quotation (RFQ) for SN74ALS540N 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 SN74ALS540N reliable?
The price and inventory of SN74ALS540N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SN74ALS540N is usually 5 days.
3.What payment methods are accepted for SN74ALS540N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SN74ALS540N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SN74ALS540N?
SN74ALS540N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SN74ALS540N 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 SN74ALS540N?
For technical support, including SN74ALS540N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SN74ALS540N requirements.
6.How does Aetrix verify that SN74ALS540N is sourced from the original manufacturer or authorized distributors?
All SN74ALS540N 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 SN74ALS540N meets industry standards.
7.What is the process for return or replacement of SN74ALS540N?
All SN74ALS540N units undergo pre-shipment inspection (PSI). If there is an issue with SN74ALS540N, 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 SN74ALS540N part is unused and in its original packaging.
Return procedure for SN74ALS540N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
SN74ALS540N 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…
