Selecting Active Pull up Buffers for High Capacitance Sensor Buses
Active pull-up buffers restore slew rates on high-capacitance sensor lines without raising low-level output voltages or violating static sink limits.
PCA9517
Repeater Function
Buffering the clock and data lines of an I2C or SMBus system enables designers to extend the physical reach of a two-wire serial bus. An integrated circuit known as the PCA9517 acts as a bidirectional buffer that isolates bus capacitance on both sides of the device. It supports multi-master controllers and is used to connect different operating voltages across the communication interface.
Voltage Translation
System engineers use this chip to connect low-voltage microcontrollers to high-voltage peripheral sensors. The PCA9517 provides level-shifting capabilities between buses operating at voltages as low as zero point nine volts and those running at five point five volts. This allows older and newer integrated circuits to communicate without risk of overvoltage damage to the more sensitive low-voltage components.
It integrates automatic direction sensing to route signals without requiring a dedicated direction control pin from the host processor.
Bus Segmentation
Splitting a heavily loaded bus into separate segments keeps rise times within the maximum limits allowed by the protocol. Each side of the PCA9517 presents an independent capacitive load, preventing cumulative capacitance from slowing transition speeds.
Signal Restoration
Open-drain outputs require pull-up resistors, which work in tandem with the buffer to pull signal lines high when released. Active circuitry inside the PCA9517 drives the lines low when required, while the external resistors define the high-state voltage. High-speed communications are thus maintained across complex server backplanes and dense industrial control systems without signal degradation.