Datasheet

Device
AVDD
0.1 µF1 µF
+3 V
AVDD1
AVSSAVSS1 DGND
DVDD
+1.8 V
0.1 µF 1 µF
0.1 µF
VREFP
VREFN
VCAP1
VCAP2
VCAP3
VCAP4
1 µF 1 µF 1 µF
10 µF
22 µF0.1 µF
RESV1
ADS131E04
ADS131E06
ADS131E08
www.ti.com SBAS561A –JUNE 2012–REVISED APRIL 2013
QUICK-START GUIDE
PCB LAYOUT
Power Supplies and Grounding
The ADS131E0x have three supplies: AVDD, AVDD1, and DVDD. Both AVDD and AVDD1 should be as quiet as
possible. AVDD1 provides the supply to the charge pump block and has transients at f
CLK
. Therefore, it is
recommended that AVDD1 and AVSS1 be star-connected to AVDD and AVSS. It is important to eliminate noise
from AVDD and AVDD1 that is non-synchronous with device operation. Each ADS131E0x supply should be
bypassed with 10-μF and a 0.1-μF solid ceramic capacitors. It is recommended to place the digital circuits [such
as digital signal processors (DSPs), microcontrollers, and field-programmable gate arrays (FPGAs)] in the
system such that the return currents on those devices do not cross the ADS131E0x analog return path. The
ADS131E0x can be powered from unipolar or bipolar supplies.
The decoupling capacitors can be surface-mount, low-cost, low-profile multi-layer ceramic. In most cases the
VCAP1 capacitor can also be a multilayer ceramic. However, in systems where the board is subjected to high- or
low-frequency vibration, it is recommend that a non-ferroelectric capacitor (such as a tantalum or class 1
capacitor, C0G or NPO for example) be installed. EIA class 2 and class 3 dielectrics (such as X7R, X5R, and
X8R) are ferroelectric. The piezoelectric property of these capacitors can appear as electrical noise coming from
the capacitor. When using the internal reference, noise on the VCAP1 node results in performance degradation.
Connecting the Device to Unipolar (+3 V or +1.8 V) Supplies
Figure 47 illustrates the ADS131E0x connected to a unipolar supply. In this example, the analog supply (AVDD)
is referenced to analog ground (AVSS) and the digital supplies (DVDD) are referenced to digital ground (DGND).
NOTE: Place the supply, reference, and VCAP1 to VCAP4 capacitors as close to the package as possible.
Figure 47. Single-Supply Operation
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 49
Product Folder Links: ADS131E04 ADS131E06 ADS131E08