SN74HCT245NSR - Octal Bus Transceiver 3-State | Texas Instruments
MPN: SN74HCT245NSR β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.42 | $0.42 |
| 10 | $0.37 | $3.70 |
| 100 | $0.29 | $29.00 |
| 500 | $0.24 | $120.00 |
| 1,000 | $0.2 | $200.00 |
SN74HCT245NSR Overview
An octal bus transceiver is a digital logic integrated circuit that buffers and transfers eight bits of data between two buses in either direction. As a member of the broader voltage-level-translation and buffer/driver family within the 74HCT high-speed CMOS-TTL-compatible logic series, it sits between bus masters (such as microcontrollers or FPGAs) and peripheral buses, providing drive strength, direction control, and high-impedance isolation.
Key features include an operating voltage range of 4.5V to 5.5V, high-current 3-state outputs that can drive bus lines directly or up to 15 LSTTL loads, and low power consumption with a maximum ICC of 80 uA. The device provides Β±6mA output drive at 5V and a low input current of 1 uA maximum. Inputs are TTL-voltage compatible, allowing direct interfacing with 5V TTL logic and many 3.3V microcontroller outputs.
Architecturally, the SN74HCT245 uses a non-inverting 8-bit transceiver core with two control pins: DIR (direction) selects the data path (A-to-B or B-to-A), and OE (output enable) active-low pin places all outputs in the high-impedance 3-state condition. The HCT CMOS process combines the low static power of CMOS with TTL input thresholds, minimizing external timing requirements per the TI datasheet.
Typical applications include microprocessor and MCU peripheral bus isolation, memory and I/O expansion buses, backplane communication in industrial controllers, and 5V legacy system interfacing where TTL-compatible inputs are required.
For reliable operation, tie OE low through a pull-down resistor when unused, and place 0.1uF decoupling capacitors close to the VCC pin on both sides of the wide-body package.
This page synthesizes distributor pricing, drop-in alternatives, pinout data, and practical design notes not consolidated in the manufacturer datasheet.
Drop-in alternatives for SN74HCT245NSR β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool β Select alternative parts for side-by-side comparison:
SN74HCT245NS
β Drop-Inπ Reference alternative (not in catalog)
SN74HCT245NSRE4
β Drop-Inπ Reference alternative (not in catalog)
SN74HCT245NSRG4
β Drop-Inπ Reference alternative (not in catalog)
SN74AHCT245NSR
β Drop-Inπ Reference alternative (not in catalog)
SN74HCT245NSR Maximum Ratings & Electrical Characteristics
| Logic Function | Octal bus transceiver, non-inverting |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Output Drive Current | Β±6 mA at 5 V |
| Typical Propagation Delay | 14 ns |
| Maximum ICC (Quiescent) | 80 uA |
| Maximum Input Current | 1 uA |
| Output Type | 3-state |
| Bus Load Capability | Up to 15 LSTTL loads |
| Input Compatibility | TTL-voltage compatible |
| Number of Bits | 8 |
| Control Pins | DIR (direction), OE (output enable, active low) |
| Operating Temperature | -40C to +85C |
| Package | SOP (NS), 20 pins, wide body |
| Mounting Type | Surface Mount |
| Marking Code | HCT245 |
| RoHS Status | Compliant |
SN74HCT245NSR Pin Configuration
| Pin 1 | DIR β Direction control: high = A to B, low = B to A |
| Pin 2 | A0 β Data port A, bit 0 |
| Pin 3 | A1 β Data port A, bit 1 |
| Pin 4 | A2 β Data port A, bit 2 |
| Pin 5 | A3 β Data port A, bit 3 |
| Pin 6 | A4 β Data port A, bit 4 |
| Pin 7 | A5 β Data port A, bit 5 |
| Pin 8 | A6 β Data port A, bit 6 |
| Pin 9 | A7 β Data port A, bit 7 |
| Pin 10 | GND β Ground |
| Pin 11 | B7 β Data port B, bit 7 |
| Pin 12 | B6 β Data port B, bit 6 |
| Pin 13 | B5 β Data port B, bit 5 |
| Pin 14 | B4 β Data port B, bit 4 |
| Pin 15 | B3 β Data port B, bit 3 |
| Pin 16 | B2 β Data port B, bit 2 |
| Pin 17 | B1 β Data port B, bit 1 |
| Pin 18 | B0 β Data port B, bit 0 |
| Pin 19 | OE β Output enable, active low; high = 3-state outputs |
| Pin 20 | VCC β Power supply, 4.5 V to 5.5 V |
Typical Applications
SN74HCT245NSR is suitable for 6 applications: Microcontroller Peripheral Bus Isolation, Industrial Backplane and PLC I/O Boards, Legacy 5V System Interfacing and Repair, Memory and SRAM Bus Expansion, Mixed 3.3V/5V Signal Interfacing (3.3V Source to 5V Load), LED and Relay Drive Glue Logic.
Microcontroller Peripheral Bus Isolation
The SN74HCT245NSR buffers an MCU general-purpose or memory-expansion bus with Β±6mA per-pin drive, allowing eight lines to fan out to multiple peripherals without violating the controller output current budget. Its TTL-compatible inputs accept standard 5V MCU signaling, and DIR/OE control enables dynamic direction switching under software control. With a 14 ns typical propagation delay, it adds negligible timing to bus cycles up to tens of MHz. Placing the transceiver at the board edge also protects the MCU from hot-plug and back-drive events, since OE sets all outputs high-impedance during power sequencing or bus arbitration.
Recommended
Industrial Backplane and PLC I/O Boards
In industrial controllers and PLC backplanes, buses cross long PCB traces and multiple card slots, requiring the 15-LSTTL-load drive capability of the SN74HCT245NSR to maintain valid logic levels. Its 4.5V to 5.5V supply tolerance accommodates noisy plant power rails, and -40C to +85C operation covers cabinet environments. The 3-state outputs allow multiple boards to share a common backplane bus, with each card's OE pin asserting only when addressed. The wide-body SOP-20 package offers 0.05-inch lead pitch that eases inspection and soldering on industrial assembly lines.
Recommended
Legacy 5V System Interfacing and Repair
Legacy industrial, telecom, and test equipment designs standardized on 5V TTL buses that the SN74HCT245NSR natively supports. Its TTL-voltage-compatible inputs make it a direct repair part for boards originally populated with 74LS245/74ALS245 devices, while cutting static power from milliwatts (bipolar) to the 80 uA maximum ICC of the HCT process. The 14 ns typical delay matches or improves on original LS-family timing, so retrofits do not perturb bus timing budgets. Reel packing (NSR suffix) suits volume refurbishment, and the pin-compatible family spans DIP for through-hole repairs.
Recommended
Memory and SRAM Bus Expansion
When expanding systems with SRAM, EEPROM, or parallel-flash devices, the SN74HCT245NSR isolates the data bus so multiple memory devices can share the same eight-bit bus with 3-state arbitration. The 1 uA maximum input current keeps loading negligible even with several transceivers cascaded, preserving signal integrity on long address/data runs. Its 14 ns typical tpd fits comfortably within 100 ns-class memory access cycles. OE gating from the memory chip-select ensures only the addressed device drives the bus, while DIR switches the data path between CPU writes and reads without external glue timing.
Recommended
Mixed 3.3V/5V Signal Interfacing (3.3V Source to 5V Load)
Many modern MCUs and FPGAs operate at 3.3V but must drive 5V peripherals. The HCT input threshold (approximately 1.4V) accepts 3.3V logic highs as valid, so the SN74HCT245NSR powered at 5V translates 3.3V controller outputs to full-swing 5V signals - a one-directional level-shift function widely used in UART, SPI, and parallel-peripheral glue logic. The Β±6mA output drive then meets 5V TTL load requirements. Designers should add a series-resistor or dedicated translator (e.g., LVC4245A) for the reverse 5V-to-3.3V direction, since 5V outputs exceed most 3.3V input ratings.
Recommended
LED and Relay Drive Glue Logic
The Β±6mA outputs and 15-LSTTL-load capability of the SN74HCT245NSR make it useful as a segment driver bank for LEDs (through resistors), optocoupler input drivers, and relay-coil transistor pre-drivers on control boards. The 3-state outputs let firmware blank entire display or output banks during startup, avoiding spurious actuation. Its 5V supply aligns with standard relay/optocoupler logic rails, and the 80 uA maximum quiescent ICC keeps standby drain low in battery-backed control panels. Series gate resistors sized for 6mA per pin keep the device within recommended drive limits in continuous duty.
Recommended
Recommended Products Summary
Engineering reference data for SN74HCT245NSR β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | SN74HCT245NS | SN74HCT245NSRE4 | SN74HCT245NSRG4 | SN74AHCT245NSR |
|---|---|---|---|---|---|
| Package | SOP-20 (NS) wide body | SOP-20 (NS) - same | SOP-20 (NS) - same | SOP-20 (NS) - same | SOP-20 (NS) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Logic Family | HCT (TTL-compatible CMOS) | HCT | HCT | HCT | AHCT (advanced, faster) |
| Supply Voltage | 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 | Β±6 mA at 5 V | Β±6 mA at 5 V | Β±6 mA at 5 V | Β±6 mA at 5 V | Β±8 mA at 5 V (higher) |
| LSTTL Load Capability | 15 loads | 15 loads | 15 loads | 15 loads | 15 loads |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| Packing | Tape & Reel (NSR suffix) | Tube / Cut Tape | Tape & Reel (E4 suffix) | Tape & Reel (G4 suffix) | Tape & Reel |
Key Differentiators
- TTL-compatible input thresholds (vs SN74HC245 (CMOS-threshold equivalent))
- Low static power consumption (vs SN74HCT245NSRE4 (same die) vs legacy 74LS245)
- Drop-in speed upgrade path (vs SN74AHCT245NSR)
Design Notes
Decouple the SN74HCT245NSR with a 100 nF ceramic capacitor placed within 5 mm of the VCC (pin 20) to GND (pin 10) path, plus one bulk 10 uF per group of four to six logic devices on the 5V rail. Because eight outputs can switch simultaneously, simultaneous-switching ground bounce is the primary noise mechanism; a solid ground plane under the wide-body SOP-20 and short return paths for A/B port traces keep glitches below TTL noise margins.
Route the A and B buses on adjacent layers with a ground reference plane between signal layers to control reflection on runs longer than about 10 cm. Keep the DIR and OE control traces away from clock lines to prevent false direction or bus contention glitches; a 10 kOhm pull-up on OE (to keep outputs disabled during reset) and a defined DIR level at power-up prevent bus fights when multiple transceivers share one backplane bus.
Never enable two transceivers driving the same bus simultaneously - brief OE overlap during direction changes causes shoot-through current and possible device stress. Insert a brief 3-state interval (OE high) between DIR transitions in firmware or logic. Also note this is a 5V-only device (4.5V to 5.5V): connecting a 5V output to a 3.3V input violates most modern MCU absolute maximum ratings, so choose LVC-family parts for bidirectional mixed-voltage buses.
Compliance Information
RoHS compliance stated for current TI SN74HCT245 production parts. REACH, halogen-free, and conflict-minerals status not stated in provided data - verify on TI product page.
