ZHCSF11B April 2016 – September 2016 ADS127L01
PRODUCTION DATA.
The ADS127L01 requires either two or three power supplies, depending on if the internal LDO is used to supply the LVDD analog supply. The AVDD analog supply is referenced to AGND, the LVDD analog supply is referenced to AGND, and the DVDD digital supply is referenced to DGND. The analog power supply can only be unipolar (for example, AVDD = 3.0 V, AGND = 0 V) and is independent of the digital power supply. If INTLDO = 0, the LVDD supply is internally generated using the AVDD supply. If INTLDO = 1, the internal LDO is disabled and LVDD supply must be externally supplied. The digital supply sets the digital I/O levels.
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. Bring the RESET/PWDN pin high after the analog and digital supplies are up, or bring the pin high with the DVDD supply (assuming the AVDD and LVDD supplies come up with or before DVDD). After all supplies are stabilized, wait for the td(POR) timing for the power-on-reset to complete before communicating with the device in order to allow the power-up reset process to complete.
Good power-supply decoupling is important to achieve optimum performance. AVDD, LVDD, and DVDD must be decoupled with at least a 1-µF capacitor, as shown in Figure 129. Place the bypass capacitors as close to the power-supply pins of the device as possible using low-impedance connections. Use multilayer 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, avoid the use of vias for connecting the capacitors to the device pins for 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.