ZHCSFJ3A July 2014 – September 2016 ADS1148-Q1
PRODUCTION DATA.
The device requires two power supplies: analog (AVDD, AVSS) and digital (DVDD, DGND). The analog power supply can be bipolar (for example, AVDD = 2.5 V, AVSS = –2.5 V) or unipolar (for example, AVDD = 3.3 V, AVSS = 0 V) and is independent of the digital power supply. The digital supply sets the digital I/O levels (with the exception of the GPIO levels that are set by the analog supply of AVDD to AVSS).
The power supplies can be sequenced in any order but in no case must any analog or digital inputs exceed the respective analog or digital power-supply voltage limits. Wait at least 216 tCLK cycles after all power supplies are stabilized before communicating with the device to allow the power-on reset process to complete.
Good power-supply decoupling is important to achieve optimum performance. AVDD, AVSS (when using a bipolar supply), and DVDD must be decoupled with at least a 0.1-µF capacitor, as shown in Figure 77. Place the bypass capacitors as close to the power-supply pins of the device as possible using low-impedance connections. Use multi-layer ceramic chip capacitors (MLCCs) that offer low equivalent series resistance (ESR) and inductance (ESL) characteristics for power-supply decoupling purposes. For very sensitive systems, or for systems in harsh noise environments, avoiding the use of vias for connecting the capacitors to the device pins can offer superior noise immunity. The use of multiple vias in parallel lowers the overall inductance and is beneficial for connections to ground planes. Connect analog and digital ground together as close to the device as possible.