ADS1291
ADS1292
ADS1292R
SBAS502A –DECEMBER 2011–REVISED MARCH 2012
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Connecting the Device to Bipolar (±1.5 V or 1.8 V) Supplies
Figure 61 illustrates the ADS1291, ADS1292, and ADS1292R 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 supply (DVDD) is referenced to the device digital ground return (DGND).
+1.5 V
+1.8 V
1 mF
0.1 mF
0.1 mF
1 mF
AVDD
DVDD
VREFP
0.1 mF
10 mF
VREFN
PGA1N
PGA1P
(1)
4.7 nF
-1.5 V
VCAP1
VCAP2
Device
PGA2N
PGA2P
4.7 nF
AVSS DGND
1 mF
1 mF
1 mF
0.1 mF
-1.5 V
NOTE: Place the capacitors for supply, reference, VCAP1, and VCAP2 as close to the package as possible.
(1) When using the ADS1292R and the channel 1 respiration function, this capacitor must be 47 nF.
Figure 61. Bipolar Supply Operation
Shielding Analog Signal Paths
As with any precision circuit, careful 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 ADS1291, ADS1292, and ADS1292R input bias
current if shielding is not implemented. Digital signals should be kept as far as possible from the analog input
signals on the PCB.
60
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