Datasheet

100W 10kW
9.09kW
10kW
OPA350
OPA365
OPA365
ADS1158
47W
10kW
2.2nF
+2.5V
+2.5V
MUXOUTN
MUXOUTP ADCINP ADCINN
-2.5V
+2.5V
-2.5V
+2.5V
-2.5V
AINCOM
REFP
REFN
AIN15
AIN0
AVSS AVDD
±10V
9.09kW
±10V
1kW
1kW
+2.5V
-2.5V
0.1 Fm
100 Fm 0.1 Fm
0.47 Fm
+
10 Fm
+
REF5040
0.1 Fm
+
10 Fm
-2.5V
0.1 Fm
+
10 Fm
¼ ¼
47W
50W
AINx
20mAInput
ADS1158
SBAS429D –JUNE 2008– REVISED MARCH 2011 www.ti.com
ANALOG INPUT CONNECTIONS When using Auto-Scan mode to sequence through
the channels, the switch time delay feature
Figure 54 shows the ADS1158 interfacing to
(programmable by registers) can be used to provide
high-level ±10V inputs, commonly used in industrial
additional settling time of the external components.
environments. In this case, bipolar power supplies are
used to avoid the need for input signal level-shifting Figure 55 illustrates the ADS1158 interfacing to
that is otherwise required with a single supply. The multiple pressure sensors that have a resistor bridge
input resistors serve both to reduce the level of the output. Each sensor is excited by the +5V single
10V input signal to within the ADC range and also supply that also powers the ADS1158, and likewise is
protect the inputs from inadvertent signal over-voltage used as the ADS1158 reference input; the 6% input
up to 30V. The external amplifiers convert the overrange capability accommodates input levels at or
single-ended inputs to a fully differential output to above V
REF
. The ratiometric connection provides
drive the ADC inputs. Driving the inputs differentially cancellation of excitation voltage drift and noise. For
maintains good linearity performance. The 2.2nF best performance, the +5V supply should be free
capacitor at the ADC inputs is required to bypass the from glitches or transients. The 5V supply input
ADC sampling currents. The 2.5V reference, amplifiers (two OPA365s) form a differential
REF3125, is filtered and buffered to provide a input/differential output buffer with the gain set to 10.
low-noise reference input to the ADC. The chop The chop feature of the ADS1158 is used to reduce
feature of the ADC can be used to reduce offset and offset and offset drift to very low levels. The 2.2nF
offset drift of the amplifiers. capacitor at the ADC inputs is required to bypass the
ADC sampling currents. The 47Ω resistors isolate the
For ±1V input signals, the input resistor divider can
operational amplifier outputs from the filter capacitor.
be removed and replaced with a series protection
resistor. For 20mA input signals, the input resistor
divider is replaced by a 50Ω resistor, connected from
each input to AINCOM.
NOTE: 0.1μF capacitors not shown.
Figure 54. Multichannel, ±10V Single-Ended Input, Bipolar Supply Operation
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Product Folder Link(s): ADS1158