Datasheet

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APPLICATION INFORMATION
BASIC CONNECTIONS
1
2
3
6
5
4
V
IN-
V
IN+
SCL
GND
V
DD
SDA
ADS1000
PositiveInput
(0Vto5V)
NegativeInput
(0Vto5V)
V
DD
V
DD
4.7 F(typ.)m
Microcontrolleror
Microprocessor
withI CPort
2
SCL
SDA
I CPull-UpResistors
1k to10k (typ.)W W
2
ADS1000
SBAS357A – SEPTEMBER 2006 – REVISED OCTOBER 2007
The ADS1000 interfaces directly to standard mode,
fast mode, and high-speed mode I
2
C controllers. Any
microcontroller I
2
C peripheral, including master-only
For many applications, connecting the ADS1000 is
and non-multiple-master I
2
C peripherals, will work
extremely simple. A basic connection diagram for the
with the ADS1000. The ADS1000 does not perform
ADS1000 is shown in Figure 9 .
clock-stretching (that is, it never pulls the clock line
The fully differential voltage input of the ADS1000 is
low), so it is not necessary to provide for this unless
ideal for connection to differential sources with
other devices are on the same I
2
C bus.
moderately low source impedance, such as bridge
Pull-up resistors are necessary on both the SDA and
sensors and thermistors. Although the ADS1000 can
SCL lines because I
2
C bus drivers are open-drain.
read bipolar differential signals, it cannot accept
The size of these resistors depends on the bus
negative voltages on either input. It may be helpful to
operating speed and capacitance of the bus lines.
think of the ADS1000 positive voltage input as
Higher-value resistors consume less power, but
noninverting, and of the negative input as inverting.
increase the transition times on the bus, limiting the
When the ADS1000 is converting, it draws current in
bus speed. Lower-value resistors allow higher speed
short spikes. The 0.1 μ F bypass capacitor supplies
at the expense of higher power consumption. Long
the momentary bursts of extra current needed from
bus lines have higher capacitance and require
the supply.
smaller pullup 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.
Figure 9. Typical Connections of the ADS1000
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