ASD1194 datasheet(64/76 Pages) TI

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ADS1198

0.1 F

1 F

AVDD

AVDD1

0.1 F

1 F

1.5V

AVSS

AVSS1

DGND

DVDD

+1.5V

+1.8V

0.1 F

1 F

VCAP1

VCAP2

VCAP3

0.1 F

VREFP

VREFN

10 F

VCAP4

WCT

1 F

1.5V

22 F

0.1 F

100pF

RESV1

5kW

10pF

AVSS

AVDD

INxP,

INxN

ADS1194, ADS1196

ADS1198

SBAS471C

– APRIL 2010 – REVISED NOVEMBER 2011

www.ti.com

Connecting the Device to Bipolar (

±1.5V/1.8V) Supplies

Figure 55 illustrates the ADS1194/6/8 connected to a bipolar supply. In this example, the analog supplies

connect to the device analog supply (AVDD). This supply is referenced to the device analog return (AVSS), and

the digital supplies (DVDD and DVDD) are referenced to the device digital ground return (DVDD).

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

Figure 55. Bipolar Supply Operation

Shielding Analog Signal Paths

As with any precision circuit, careful printed circuit board (PCB) layout ensures the best performance. It is

essential to make short, direct interconnections and avoid stray wiring capacitance

—particularly at the analog

input pins and AVSS. These analog input pins are high-impedance and extremely sensitive to extraneous noise.

The AVSS pin should be treated as a sensitive analog signal and connected directly to the supply ground with

proper shielding. Leakage currents between the PCB traces can exceed the input bias current of the

ADS1194/6/8 if shielding is not implemented. Digital signals should be kept as far as possible from the analog

input signals on the PCB.

Analog Input Structure

The analog input of the ADS119x is shown in Figure 56.

Figure 56. Analog Input Protection Circuit

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