Datasheet

ADS1198
0.1 Fm1 Fm
AVDD AVDD1
0.1 Fm1 Fm
-1.5V
AVSSAVSS1
DGND
DVDD
+1.5V
+1.8V
0.1 Fm 1 Fm
VCAP1
VCAP2
VCAP3
0.1 Fm
VREFP
VREFN
10 Fm
VCAP4
WCT
1 Fm 1 Fm1 Fm
-1.5V
22 Fm0.1 Fm100pF
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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Product Folder Link(s): ADS1194 ADS1196 ADS1198