Datasheet

ADS1110
SBAS276A − MARCH 2003 − REVISED NOVEMBER 2003
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13
APPLICATIONS INFORMATION
The sections that follow give example circuits and tips for
using the ADS1110 in various situations.
BASIC CONNECTIONS
For many applications, connecting the ADS1110 is
extremely simple. A basic connection diagram for the
ADS1110 is shown in Figure 4.
Figure 4. Typical Connections of the ADS1110
The fully differential voltage input of the ADS1110 is ideal
for connection to differential sources with moderately low
source impedance, such as bridge sensors and
thermistors. Although the ADS1110 can read bipolar
differential signals, it cannot accept negative voltages on
either input. It may be helpful to think of the ADS1110
positive voltage input as non−inverting, and of the negative
input as inverting.
When the ADS1110 is converting, it draws current in short
spikes. The 0.1µF bypass capacitor supplies the
momentary bursts of extra current needed from the supply.
The ADS1110 interfaces directly to standard mode, fast
mode, and high−speed mode I
2
C controllers. Any
microcontroller’s I
2
C peripheral, including master-only
and non-multiple-master I
2
C peripherals, will work with the
ADS1110. The ADS1110 does not perform
clock-stretching (i.e., it never pulls the clock line low), so
it is not necessary to provide for this unless
clock-stretching devices are on the same I
2
C bus.
Pull-up resistors are necessary on both the SDA and SCL
lines because I
2
C bus drivers are open-drain. The size of
these resistors depends on the bus operating speed and
capacitance of the bus lines. Higher-value resistors
consume less power, but increase the transition times on
the bus, limiting the bus speed. Lower-value resistors
allow higher speed at the expense of higher power
consumption. Long bus lines have higher capacitance and
require smaller pull-up resistors to compensate. The
resistors should not be too small; if they are, the bus drivers
may not be able to pull the bus lines low.
CONNECTING MULTIPLE DEVICES
Connecting multiple ADS1110s to a single bus is trivial.
The ADS1110 is available in eight different versions, each
of which has a different I
2
C address. An example showing
three ADS1110s connected on a single bus is shown in
Figure 5. Up to eight ADS1110s (provided their addresses
are different) can be connected to a single bus.
Figure 5. Connecting Multiple ADS1110s
Note that only one set of pull-up resistors is needed per
bus. The pull-up resistor values may need to be lowered
slightly to compensate for the additional bus capacitance
presented by multiple devices and increased line length.