This dual bidirectional I2C buffer is operational at 2.3V to 3.6V Vcc. The PCA9515A is a BiCMOS integrated circuit intended for I2C bus and SMBus systems applications. The device contains two identical bidirectional open-drain buffer circuits that enable I2C and similar bus systems to be extended without degradation of system performance.
The PCA9515A buffers both the serial data (SDA) and serial clock (SCL) signals on the I4C bus, while retaining all the operating modes and features of the I2C system. This enables two buses of 400-pF bus capacitance to be connected in an I2C application.
The I2C bus capacitance limit of 400 pF restricts the number of devices and bus length. Using the PCA9515A enables the system designer to isolate two halves of a bus, accommodating more I2C devices or longer trace lengths. The PCA9515A has an active-high enable (EN) input with an internal pullup, which allows the user to select when the repeater is active. This can be used to isolate a badly behaved slave on power-up reset. It never should change state during an IC operation, because disabling during a bus operation hangs the bus, and enabling part way through a bus cycle could confuse the I2C parts being enabled. The EN input should change state only when the global bus and the repeater port are in an idle state, to prevent system failures.
The PCA9515A also can be used to run two buses: one at 5V interface levels and the other at 3.3V interface levels, or one at 400kHz operating frequency and the other at 100kHz operating frequency. If the two buses are operating at different frequencies, the 100kHz bus must be isolated when the 400kHz operation of the other bus is required. If the master is running at 400kHz， the maximum system operating frequency may be less than 400 kHz, because of the delays that are added by the repeater.