ZHCSJK4G June 2009 – March 2021 PCA9548A
PRODUCTION DATA
For PCB layout of the PCA9548A, common PCB layout practices must be followed but additional concerns related to high-speed data transfer such as matched impedances and differential pairs are not a concern for I2C signal speeds. It is common to have a dedicated ground plane on an inner layer of the board and pins that are connected to ground must have a low-impedance path to the ground plane in the form of wide polygon pours and multiple vias. By-pass and de-coupling capacitors are commonly used to control the voltage on the VCC pin, using a larger capacitor to provide additional power in the event of a short power supply glitch and a smaller capacitor to filter out high-frequency ripple.
In an application where voltage translation is not required, all VDPUX voltages and VCC could be at the same potential and a single copper plane could connect all of pull-up resistors to the appropriate reference voltage. In an application where voltage translation is required, VDPUM and VDPU0 – VDPU7 may all be on the same layer of the board with split planes to isolate different voltage potentials.
To reduce the total I2C bus capacitance added by PCB parasitics, data lines (SCn and SDn) must be a short as possible and the widths of the traces must also be minimized (For example, 5-10 mils depending on copper weight).