COMBOSMARTMETER datasheet(49/60 Pages) TI1

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Device

AVDD

0.1 µF

1 µF

+3 V

AVDD1

AVSS

AVSS1

DGND

DVDD

+1.8 V

0.1 µF

1 µF

0.1 µF

VREFP

VREFN

VCAP1

VCAP2

VCAP3

VCAP4

1 µF

10 µF

22 µF

0.1 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 fCLK. 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

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Product Folder Links: ADS131E04 ADS131E06 ADS131E08

COMBOSMARTMETER Datasheet(PDF) 49 Page - Texas Instruments

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