JAJSLQ5C April 2021 – September 2022 ADS127L11
PRODUCTION DATA
To achieve data sheet performance, use a minimum four-layer PCB board with the inner layers dedicated to ground and power planes. Best performance is achieved by combining the analog and digital grounds on a single, unbroken ground plane. In some layout geometries, however, using separate analog and digital grounds may be necessary to help direct digital currents away from the analog ground (such as pulsing LED indicators, relays, and so on). In this case, consider separate ground return paths for these loads. When separate analog and digital grounds are used, join the grounds at the ADC.
Use the power plane layer to route the power supplies to the ADC.
The top and bottom layers route the analog and digital signals. Route the input signal as a matched differential pair throughout the signal chain to reduce differential noise coupling. Avoid crossing or adjacent placement of digital signals with the analog signals. This layout is especially true for high-frequency digital signals such as the clock input, and SPI signals, SCLK, and SDO/DRDY. The pin placement of both ADC package options minimizes the need to cross digital and analog signals.
Place the voltage reference close to the ADC. Orient the reference such that the reference ground pin is close to the ADC REFN pin. Place the reference input bypass capacitors directly at the ADC pins. Use reference bypass capacitors for each ADC in multichannel systems and connect the reference ground pin to the ground plane (or to AVSS in some bipolar supply systems) at one point and route REFP and REFN as paired traces to each ADC.