Overview
The SN74LVC4245A, produced by Texas Instruments, is an 8-bit (octal) noninverting bus transceiver designed for asynchronous communication between data buses. This device features two separate supply rails: the B port operates at 3.3 V (VCCB), and the A port operates at 5 V (VCCA), enabling translation between 3.3-V and 5-V environments. The device can transmit data from the A bus to the B bus or from the B bus to the A bus, controlled by the direction-control (DIR) input. Additionally, the output-enable (OE) input allows the device to be disabled, effectively isolating the buses. The control circuitry is powered by VCCA, making it versatile for various bus interface applications.
Key Specifications
| Parameter | Condition | Min | Typ | Max | Unit |
|---|---|---|---|---|---|
| VCCA Supply Voltage Range | - | -0.5 | - | 6.5 | V |
| VI Input Voltage Range (A port) | - | -0.5 | - | VCCA + 0.5 | V |
| VO Output Voltage Range (A port) | - | -0.5 | - | VCCA + 0.5 | V |
| IO Continuous Output Current | - | - | - | ±50 | mA |
| Tstg Storage Temperature Range | - | -65 | - | 150 | °C |
| tPHL Propagation Delay Time (A to B) | VCCA = 5 V, VCCB = 2.7 V to 3.6 V | 6.1 | - | 6.3 | ns |
| tPLH Propagation Delay Time (A to B) | VCCA = 5 V, VCCB = 2.7 V to 3.6 V | 5 | - | 6.7 | ns |
| RθJA Junction-to-Ambient Thermal Resistance | - | - | - | 90.7 (DB), 100.6 (PW) | °C/W |
Key Features
- 8-bit (octal) noninverting bus transceiver with two separate supply rails (VCCA = 5 V, VCCB = 3.3 V) for voltage translation between 3.3-V and 5-V environments.
- Direction-control (DIR) input to select data transmission direction between A and B buses.
- Output-enable (OE) input to disable the device and isolate the buses.
- 24 mA drive at 3-V supply, suitable for heavier loads and longer traces.
- Low VIH (input high voltage) allows for 3.3-V to 5-V translation.
- CMOS technology with balanced output drive.
- Available in DB (SSOP), DW (SOIC), and PW (TSSOP) packages.
Applications
The SN74LVC4245A is designed for a variety of bus interface applications where output drive or PCB trace length is a concern. It is particularly useful in systems that require asynchronous communication between data buses operating at different voltage levels. Typical applications include:
- Interface between 3.3-V and 5-V logic systems.
- High-drive CMOS applications requiring robust output drive.
- Systems with long PCB traces or heavy loads).
Q & A
- What is the primary function of the SN74LVC4245A?
The SN74LVC4245A is an 8-bit noninverting bus transceiver designed for asynchronous communication between data buses, allowing voltage translation between 3.3-V and 5-V environments).
- How does the device control data transmission direction?
The direction-control (DIR) input determines whether data is transmitted from the A bus to the B bus or from the B bus to the A bus).
- What is the purpose of the output-enable (OE) input?
The output-enable (OE) input can be used to disable the device, effectively isolating the buses).
- What are the typical supply voltage ranges for the A and B ports?
The A port (VCCA) operates at 4.5 V to 5.5 V, and the B port (VCCB) operates at 2.7 V to 3.6 V).
- What are the propagation delay times for the device?
The propagation delay times (tPHL and tPLH) range from 5 ns to 6.7 ns depending on the direction of data transmission and load conditions).
- What are the thermal resistance values for the device?
The junction-to-ambient thermal resistance (RθJA) is approximately 90.7 °C/W for the DB package and 100.6 °C/W for the PW package).
- What packages is the SN74LVC4245A available in?
The device is available in DB (SSOP), DW (SOIC), and PW (TSSOP) packages).
- Why is the SN74LVC4245A suitable for high-drive applications?
The device offers a 24 mA drive at 3-V supply, making it suitable for heavier loads and longer traces).
- What should be considered when designing with the SN74LVC4245A?
Care should be taken to avoid bus contention, and routing and load conditions should be considered to prevent ringing due to the high drive and fast edges).
- Can the SN74LVC4245A be used in place of other '245 devices without board re-layout?
Yes, the device's pinout allows it to be used in place of normal all-3.3-V or all-5-V 20-pin '245 devices without board re-layout).
