Overview
The SN74ALS245ANSR is an octal bus transceiver with 3-state outputs, designed for asynchronous two-way communication between data buses. This device is part of the 74ALS series from Texas Instruments, known for its advanced Schottky logic technology. It is used to facilitate data transmission between two buses, A and B, with the ability to isolate the buses when necessary.
Key Specifications
| Parameter | Min | Typ | Max | Unit |
|---|---|---|---|---|
| High-level input voltage (VIH) | 2 | - | - | V |
| Low-level input voltage (VIL) | 0.8 | - | - | V |
| High-level output voltage (VOH) | 2.4 | 3.4 | - | V |
| Low-level output voltage (VOL) | 0.4 | - | - | V |
| Propagation delay time (tPLH, tPHL) | 8 | - | - | ns |
| Output enable time to high level (tPLZ) | 25 | - | 40 | ns |
| Output disable time from low level (tPHZ) | 15 | - | 28 | ns |
| Operating temperature range | 0 | - | 70 | °C |
| Power supply voltage (VCC) | 4.5 | - | 5.5 | V |
Key Features
- 3-State Outputs: The outputs can drive bus lines directly and can be put into high impedance mode through the OE pin.
- PNP Inputs: Reduces DC loading on bus lines.
- Hysteresis on Bus Inputs: Improves noise margins.
- Direction Control: Data transmission can be controlled from A to B or from B to A using the DIR pin.
- Output Enable: The OE pin can disable the device, effectively isolating the buses.
- Fast Propagation Delay: Typical propagation delay times of 8 ns.
Applications
- Building Automation: Used in various building automation systems for data communication.
- Electronic Point of Sale: Utilized in POS systems for reliable data transmission.
- Factory Automation and Control: Employed in industrial automation to ensure robust data communication.
- Test and Measurement: Used in test and measurement equipment for accurate data transfer.
- Ribbon Cables and Back Plane Buses: Enhances signal strength and drive capability over long cables and back planes.
Q & A
- What is the primary function of the SN74ALS245ANSR?
The primary function is to facilitate asynchronous two-way communication between data buses A and B.
- How does the direction of data transmission get controlled?
The direction of data transmission is controlled using the DIR pin. A low level on DIR sets the direction from B to A, while a high level sets it from A to B.
- What is the purpose of the OE pin?
The OE (output enable) pin can disable the device, putting all outputs into high impedance mode and effectively isolating the buses.
- What are the typical propagation delay times for this device?
The typical propagation delay times are 8 ns.
- What is the operating temperature range for the SN74ALS245ANSR?
The operating temperature range is from 0°C to 70°C.
- What is the recommended power supply voltage range?
The recommended power supply voltage range is from 4.5 V to 5.5 V.
- How does the device improve signal strength over long cables?
The device improves signal strength by acting as a high-current drive transceiver, enhancing the signal quality over long ribbon cables and back planes.
- What are some common applications of the SN74ALS245ANSR?
Common applications include building automation, electronic point of sale, factory automation, test and measurement, and use in ribbon cables and back plane buses.
- What are the benefits of PNP inputs in this device?
The PNP inputs reduce DC loading on bus lines, which helps in maintaining signal integrity.
- How does hysteresis on bus inputs benefit the device?
Hysteresis on bus inputs improves noise margins, making the device more robust against noise and signal degradation.
