11.1 Layout Guidelines
At minimum, a two layer board is required for a typical pressure-sensing application. PCB layers must be separated by analog and digital signals. The pin map of the device is such that the power and digital signals are on the opposite side of the analog signal pins. Best practices for PGA302 device layout are as follows:
- The analog input signal pins, VINPP, VINPN, VINTP, and VINTN are the most susceptible to noise, and must be routed as directly to the sensor as possible. Additionally, each pair of positive and negative inputs must be routed in differential pairs with matching trace length, and both traces as close together as possible throughout their length. This routing is critical in reducing EMI and offset to provide the most accurate measurements.
- TI recommended separating the grounds to reduce noise at the analog input of the device. Capacitors to ground for ESD protection on the analog input signal pins must go first to this separate ground and be as close to the pins as possible to reduce the length of the ground wire. The analog input ground can be connected to the main ground with a ferrite bead, but acopper trace, a 0-Ω resistor can be used instead.
- The decoupling capacitors for DVDD and VDD must be placed as close to the pins as possible.
- All digital communication must be routed as far away from the analog input signal pins as possible. This includes the SCL and SDA pins, as well as the VDD pin when using OWI communication.