ASD1194 datasheet(63/76 Pages) TI

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ADS1198

AVDD

0.1 F

1 F

+3V

AVDD1

AVSS

AVSS1

DGND

DVDD

+1.8V

0.1 F

1 F

0.1 F

VREFP

VREFN

VCAP1

VCAP2

VCAP3

VCAP4

WCT

100pF

1 F

10 F

22 F

0.1 F

RESV1

ADS1194, ADS1196

ADS1198

www.ti.com

SBAS471C

– APRIL 2010 – REVISED NOVEMBER 2011

QUICK-START GUIDE

PCB LAYOUT

Power Supplies and Grounding

The ADS1194/6/8 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 the ADS1194/6/8 operation. Each supply of the

ADS1194/6/8 should be bypassed with 1

μF and a 0.1μF solid ceramic capacitors. It is recommended that

placement of the digital circuits (DSP, microcontrollers, FPGAs, etc.) in the system is done such that the return

currents on those devices do not cross the analog return path of the ADS1194/6/8. The ADS1194/6/8 can be

powered from unipolar or bipolar supplies.

The capacitors used for decoupling can be of the surface-mount, low-cost, low-profile, multi-layer ceramic type.

In most cases, the VCAP1 capacitor can also be a multi-layer ceramic, but in systems where the board is

subjected to high or low frequency vibration, it is recommend to install a non-ferroelectric capacitor such as a

tantalum or class 1 capacitor (for example, C0G or NPO). EIA class 2 and class 3 dielectrics (such as X7R, X5R,

X8R, etc.) are ferroelectric. The piezoelectric property of these capacitors can appear as electrical noise coming

from the capacitor. When using internal reference, noise on the VCAP1 node results in performance degradation.

Connecting the Device to Unipolar (+3V/+1.8V) Supplies

Figure 54 illustrates the ADS1194/6/8 connected to a unipolar supply. In this example, analog supply (AVDD) is

referenced to analog ground (AVSS) and digital supplies (DVDD) are referenced to digital ground (DGND).

NOTE: Place the capacitors for supply, reference, WCT, and VCAP1 to VCAP4 as close to the package as possible.

Figure 54. Single-Supply Operation

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Product Folder Link(s): ADS1194 ADS1196 ADS1198

ASD1194 Datasheet(PDF) 63 Page - Texas Instruments

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