ADS1194 datasheet(67/80 Pages) TI

67 / 80 page

ADS1298

AVDD

0.1 F

10 F

+3V

AVDD1

AVSS

AVSS1

DGND

DVDD

+1.8V

0.1 F

10 F

0.1 F

VREFP

VREFN

VCAP1

VCAP2

VCAP3

VCAP4

WCT

100pF

1 F

10 F

22 F

0.1 F

ADS1294

, ADS1296

ADS1298

www.ti.com

SBAS459E – JANUARY 2010 – REVISED AUGUST 2010

GUIDE TO GET UP AND RUNNING

PCB LAYOUT

Power Supplies and Grounding

The ADS1294/6/8 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 ADS1294/6/8 operation. Each supply of the

ADS1294/6/8 should be bypassed with 10mF and a 0.1mF 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 ADS1294/6/8. The ADS1294/6/8 can be

powered from unipolar or bipolar supplies.

The capacitors used for decoupling can be surface-mount, low-cost, or low-profile multi-layer ceramic. In most

cases, the VCAP1 capacitor can also be a multi-layer ceramic. However, in systems where the board is

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

tantalum or class 1 capacitor (for example, C0G or NPO) be installed. 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 the internal reference, the noise on the VCAP1 node results in

performance degradation.

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

Figure 61 illustrates the ADS1294/6/8 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 61. Single-Supply Operation

Submit Documentation Feedback

Product Folder Link(s): ADS1294 ADS1296 ADS1298

ADS1194 Datasheet(PDF) 67 Page - Texas Instruments

ADS1194 Datasheet(HTML) 67 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

Datasheet Download

Link URL