Overview
The PCA9517DRG4, produced by Texas Instruments, is a 2-bit level-translating 400-kHz I2C/SMBus buffer/repeater. This device is designed to extend I2C and SMBus systems by allowing the connection of two buses with up to 400-pF bus capacitance each. It supports voltage-level translation between low voltages (as low as 0.9 V) and higher voltages (2.7 V to 5.5 V), making it suitable for mixed-mode applications. The PCA9517 also enables the isolation of two halves of a bus for voltage and capacitance, enhancing system flexibility and reliability.
Key Specifications
| Parameter | Value | Description |
|---|---|---|
| Operating Supply Voltage Range | 0.9 V to 5.5 V | Voltage range for both VCCA and VCCB |
| I2C Bus Frequency | Up to 400 kHz | Maximum frequency for I2C/SMBus operations |
| Bus Capacitance | Up to 400 pF per bus | Maximum capacitance for each connected bus |
| Input/Output Voltage Tolerance | Up to 5.5 V | Overvoltage tolerance for inputs and I/Os even when unpowered |
| Enable Input | Active-High | Internal pullup to VCCB |
| Driver Enable Conditions | VCCA > 0.8 V, VCCB > 2.5 V | Conditions for enabling the drivers |
Key Features
- Voltage-Level Translation: Supports translation between low voltages (down to 0.9 V) and higher voltages (2.7 V to 5.5 V).
- Bus Extension and Isolation: Allows the connection of two buses with up to 400-pF bus capacitance each and isolates two halves of a bus for voltage and capacitance.
- Active-High Enable Input: With an internal pullup to VCCB, allowing selective activation of the repeater.
- Open-Drain I2C I/O: Compatible with standard I2C systems, requiring pullup resistors.
- Lockup-Free Operation: Ensures reliable operation without bus lockups.
- Multiple Device Connection: Supports star topography and series connection of multiple PCA9517s without offset voltage buildup.
Applications
- Mixed-Mode Systems: Ideal for systems requiring voltage-level translation between different voltage domains.
- Extended I2C/SMBus Systems: Useful for extending the reach of I2C/SMBus buses in complex systems.
- Bus Isolation: Suitable for isolating sections of a bus to manage voltage and capacitance issues.
- Industrial and Automotive Systems: Can be used in various industrial and automotive applications requiring reliable I2C/SMBus communication.
Q & A
- What is the primary function of the PCA9517?
The PCA9517 is a 2-bit level-translating 400-kHz I2C/SMBus buffer/repeater designed to extend and isolate I2C/SMBus buses.
- What is the operating supply voltage range for the PCA9517?
The operating supply voltage range is from 0.9 V to 5.5 V for both VCCA and VCCB.
- Can the PCA9517 handle high bus capacitance?
Yes, it can handle up to 400-pF bus capacitance per connected bus.
- Is the PCA9517 tolerant to overvoltage?
Yes, all inputs and I/Os are overvoltage tolerant up to 5.5 V, even when the device is unpowered.
- How does the enable input work on the PCA9517?
The PCA9517 has an active-high enable input with an internal pullup to VCCB, allowing selective activation of the repeater.
- Can multiple PCA9517s be connected in series?
Yes, multiple PCA9517s can be connected in series (A side to B side) without any buildup in offset voltage and with only time-of-flight delays to consider.
- Does the PCA9517 support clock stretching and arbitration?
No, the PCA9517 does not support clock stretching and arbitration across the repeater.
- What are the conditions for enabling the drivers on the PCA9517?
The drivers are enabled when VCCA is above 0.8 V and VCCB is above 2.5 V.
- Can the PCA9517 be used in star topography configurations?
Yes, the A side of two or more PCA9517s can be connected together to allow a star topography with the A side on the common bus.
- Is the PCA9517 suitable for safety-critical applications?
While it is reliable, it is not recommended for new designs, and specific considerations should be taken for safety-critical applications.
