SN74HCT240PWR - Octal Inverting 3-State Buffer | TI TSSOP-20
MPN: SN74HCT240PWR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.49 | $0.49 |
| 10 | $0.42 | $4.20 |
| 100 | $0.3 | $30.00 |
| 500 | $0.24 | $120.00 |
| 1,000 | $0.2 | $200.00 |
| 3,000 | $0.16 | $480.00 |
SN74HCT240PWR Overview
A buffer and line driver is a digital logic device that amplifies and isolates a signal between a source and a load. In digital design hierarchy, buffers and line drivers sit between general-purpose logic gates (inverters, NAND, flip-flops) and transceivers/bus switches; they regenerate weak or fan-out-limited signals without changing their logic meaning. The 'inverting' variant flips the logic level - a high input produces a low output - which is useful for active-low control signals and bus arbitration. The 3-state output feature adds a high-impedance state controlled by an output-enable pin, allowing multiple drivers to share a bus without contention.
Key features of the SN74HCT240 include typical output drive of +/-6 mA at 5 V, low input current of +/-1 uA maximum, and a propagation delay of approximately 13 ns (tPLH/tPHL) at 25 C and 5 V VCC. The HCT logic family accepts TTL-level inputs while providing CMOS-level output swings, making it a drop-in interface between legacy 5 V TTL peripherals and modern CMOS logic. Two independent output-enable pins (1OE, 2OE) allow half-chip control for split-bus architectures.
Internally, the device uses CMOS fabrication with TTL-compatible input thresholds of 0.8 V (VIL) and 2.0 V (VIH), ensuring interoperability with 5 V TTL peripherals while maintaining CMOS low-power quiescent current of 40 uA maximum. The output stage uses a complementary push-pull structure that delivers symmetric rise and fall times.
Typical applications include bus buffering between microcontrollers and memory, signal isolation on address/data lines, LED driving arrays, and general-purpose signal conditioning in industrial controls and instrumentation. The wide operating temperature range of -40 C to +85 C supports both commercial and industrial environments.
When designing with the SN74HCT240, ensure that the output-enable pins are tied to a valid logic level (not left floating) to prevent the outputs from entering an indeterminate state. For high-speed buses, place a 0.1 uF decoupling capacitor as close as possible to the VCC pin and route output traces with controlled impedance.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found on a single manufacturer or distributor page - including same-brand SN74HCT244PWR (non-inverting variant) and cross-brand equivalents from onsemi (MC74HCT240ADTR2G) and NXP, enabling engineers to evaluate substitutes quickly.
Drop-in alternatives for SN74HCT240PWR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
SN74HCT244PWR
✅ Drop-In📋 Reference alternative (not in catalog)
SN74HCT240PWT
✅ Drop-In📋 Reference alternative (not in catalog)
SN74HCT240PW
✅ Drop-In📋 Reference alternative (not in catalog)
SN74HCT240PWRG4
✅ Drop-In📋 Reference alternative (not in catalog)
MC74HCT240ADTR2G
✅ Drop-In📋 Reference alternative (not in catalog)
CD74HCT240PW
✅ Drop-In📋 Reference alternative (not in catalog)
SN74HCT240PWR Maximum Ratings & Electrical Characteristics
| Function | Buffer/Line Driver, Inverting |
| Number of Elements | 2 |
| Bits per Element | 4 |
| Output Type | 3-State |
| Logic Family | HCT (TTL-compatible CMOS) |
| Supply Voltage (VCC) | 4.5 V to 5.5 V |
| Input Logic Levels (VIL/VIH) | 0.8 V / 2.0 V (TTL) |
| High-Level Output Current (IOH) | -6 mA (min) |
| Low-Level Output Current (IOL) | 6 mA (min) |
| Quiescent Current (ICC) | 40 uA (max) |
| Operating Temperature Range | -40 C to +85 C |
| Package | TSSOP-20 (PW) |
| Mounting Type | Surface Mount |
| MSL Level | 1 (unlimited) |
| RoHS Status | Compliant |
| Lead-Free | Yes |
| Number of Output Enables | 2 (1OE, 2OE, active-low) |
| Marking Code | HT240 |
SN74HCT240PWR Pin Configuration
| Pin 1 | 1OE-bar — Output enable for bank 1, active low (LOW = outputs enabled) |
| Pin 2 | 1A0 — Bank 1 data input 0 |
| Pin 3 | 2Y3 — Bank 2 inverting output 3 |
| Pin 4 | 1A1 — Bank 1 data input 1 |
| Pin 5 | 2Y2 — Bank 2 inverting output 2 |
| Pin 6 | 1A2 — Bank 1 data input 2 |
| Pin 7 | 2Y1 — Bank 2 inverting output 1 |
| Pin 8 | 1A3 — Bank 1 data input 3 |
| Pin 9 | 2Y0 — Bank 2 inverting output 0 |
| Pin 10 | GND — Ground reference |
| Pin 11 | 2A3 — Bank 2 data input 3 |
| Pin 12 | 1Y0 — Bank 1 inverting output 0 |
| Pin 13 | 2A2 — Bank 2 data input 2 |
| Pin 14 | 1Y1 — Bank 1 inverting output 1 |
| Pin 15 | 2A1 — Bank 2 data input 1 |
| Pin 16 | 1Y2 — Bank 1 inverting output 2 |
| Pin 17 | 2A0 — Bank 2 data input 0 |
| Pin 18 | 1Y3 — Bank 1 inverting output 3 |
| Pin 19 | 2OE-bar — Output enable for bank 2, active low (LOW = outputs enabled) |
| Pin 20 | VCC — Supply voltage (4.5 V to 5.5 V) |
Typical Applications
SN74HCT240PWR is suitable for 6 applications: Microcontroller Bus Buffering, Memory Address/Data Line Isolation, LED Driver and Display Multiplexing, Industrial Control Signal Conditioning, Test and Measurement Equipment, Communication Interface Line Driving.
Microcontroller Bus Buffering
The SN74HCT240PWR is widely deployed between a 5 V microcontroller or ASIC and external memory or peripheral buses that exceed the source driver's fan-out capability. With +/-6 mA output drive at 5 V and 3-state outputs controlled by independent enable pins (1OE-bar, 2OE-bar), the HCT240 can buffer 8 address/data lines simultaneously and isolate them during bus relinquish cycles. Place the buffer within 50 mm of the MCU with a 0.1 uF decoupling cap on VCC; the TTL-compatible inputs accept standard MCU GPIO drive without level shifting, and the inverting function is acceptable for active-low control signals or where downstream logic already includes an inversion stage.
Recommended
Memory Address/Data Line Isolation
In multi-bank memory architectures (e.g., dual SRAM, bank-switched flash), the SN74HCT240PWR isolates address and data lines between memory banks and the shared bus, preventing contention during read/write cycles. The two 4-bit elements can be enabled independently to gate half the bus, enabling byte-wise control of memory access. The TTL-compatible inputs interface directly with 5 V memory controllers while the 3-state outputs release the bus cleanly during bank switch. Operating at 5 V VCC with -40 C to +85 C range, the HCT240 suits industrial memory modules where signal integrity across long PCB traces must be preserved.
Recommended
LED Driver and Display Multiplexing
The SN74HCT240PWR's +/-6 mA per-output drive is well suited to driving low-current LED arrays and 7-segment display digit/segment lines, especially in multiplexed display panels where each buffer output sinks or sources LED current directly. The inverting function makes it natural for common-anode LED configurations where a logic-low signal activates the LED. With two independent output-enable pins, designers can pulse-width-modulate brightness on one bank while the other bank drives static segments. The TSSOP-20 footprint saves PCB area in compact HMI modules and industrial control panels.
Recommended
Industrial Control Signal Conditioning
In PLC and industrial automation systems, the SN74HCT240PWR conditions 5 V logic signals traveling between isolated sections, sensor interfaces, and actuator drivers. The TTL-compatible inputs handle noisy sensor lines, while the high-current CMOS outputs cleanly drive optocouplers, relays, and 24 V-level translators downstream. The wide -40 C to +85 C operating range supports factory-floor deployments, and the 3-state outputs allow multi-master bus arbitration on RS-485 / Modbus RTU links when paired with a transceiver. Place the buffer close to the connector side of an isolation barrier to regenerate the signal before it crosses.
Recommended
Test and Measurement Equipment
Bench instruments such as logic analyzers, protocol testers, and pattern generators use the SN74HCT240PWR to buffer and route test signals between the DUT interface and the instrument's main controller. The two output-enable pins allow the instrument to tri-state the probe outputs when not actively driving the bus, preventing back-driving the DUT. The HCT logic family accepts TTL probe inputs from legacy test fixtures, and the symmetric +/-6 mA drive preserves edge fidelity on cables up to 0.5 m. The TSSOP-20 footprint fits densely populated probe-interface PCBs.
Recommended
Communication Interface Line Driving
In legacy serial communication interfaces (RS-232 level shifters, parallel printer ports, SCSI interfaces), the SN74HCT240PWR drives long PCB traces or cables where the source device cannot meet the required current or voltage swing. The inverting function is useful for active-low handshake lines such as CTS, RTS, and ACK in parallel port designs. With 3-state outputs, multiple peripherals can share a bus segment with arbitration handled by the OE-bar pins. The TTL-compatible inputs interface directly with UARTs and parallel port controllers running at 5 V.
Recommended
Recommended Products Summary
Engineering reference data for SN74HCT240PWR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SN74HCT244PWR | SN74HCT240PWT | MC74HCT240ADTR2G | CD74HCT240PW |
|---|---|---|---|---|---|
| Package | TSSOP-20 (PW) | TSSOP-20 (PW) - same | TSSOP-20 (PW) - same | TSSOP-20 (PW) - same | TSSOP-20 (PW) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | onsemi | Texas Instruments |
| Function | Inverting buffer | Non-inverting buffer | Inverting buffer (same as this) | Inverting buffer (same as this) | Inverting buffer (same as this) |
| VCC Range | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V | 4.5 V to 5.5 V |
| Output Drive (IOL/IOH) | +/-6 mA | +/-6 mA | +/-6 mA | +/-6 mA | +/-6 mA |
| Output Type | 3-State | 3-State | 3-State | 3-State | 3-State |
| Input Logic Levels | TTL (0.8V / 2.0V) | TTL (0.8V / 2.0V) | TTL (0.8V / 2.0V) | TTL (0.8V / 2.0V) | TTL (0.8V / 2.0V) |
| Operating Temperature | -40 C to +85 C | -40 C to +85 C | -40 C to +85 C | -55 C to +125 C | -40 C to +85 C |
Key Differentiators
- Wide cross-brand second-source availability (vs MC74HCT240ADTR2G (onsemi))
- Pin-compatible non-inverting family member (vs SN74HCT244PWR)
- Independent dual-bank output enables (vs Single-enable octal buffers (e.g., SN74HCT241))
Design Notes
Place a 0.1 uF ceramic decoupling capacitor as close as possible to the VCC pin (pin 20) of the SN74HCT240PWR, with the ground return via a short trace to the GND pin (pin 10). For designs with multiple HCT buffers on the same board, add a bulk 1-10 uF tantalum or aluminum polymer cap near the power-entry point to handle simultaneous switching transients. The HCT240 draws brief current spikes during output transitions that can corrupt the 5 V rail if not decoupled; even at low clock rates, peak currents can exceed 30 mA per output pair switching simultaneously.
When using the SN74HCT240PWR to drive buses longer than 50 mm or cables, add a 22-33 ohm series damping resistor at each output to limit ringing and over/undershoot. The HCT240 outputs can drive 50 pF loads cleanly at 5 V VCC, but heavier loads or long traces introduce transmission-line effects that may exceed the device's +/-6 mA drive rating during edge transitions. For multi-receiver buses, place a 10 kohm pull-up or pull-down on each line to define the logic level when the OE-bar pin disables all outputs, preventing floating-bus oscillations.
Do not leave the 1OE-bar (pin 1) or 2OE-bar (pin 19) pins floating - they are active-low inputs and will float to an indeterminate logic level if not driven, causing the outputs to enter an undefined state. Tie unused OE-bar pins directly to GND through a 10 kohm resistor if the bank is permanently enabled, or to a GPIO if software-controlled. Also avoid operating the SN74HCT240PWR below 4.5 V VCC; the HCT input thresholds are specified only at 5 V nominal, and operation at 3.3 V will cause unpredictable input behavior and reduced noise margin.
Compliance Information
RoHS and lead-free confirmed via TI product page. REACH and conflict-minerals compliance available via TI environmental portal. Not AEC-Q100 qualified - industrial grade only.
