LTC2431 Linear Technology, LTC2431 Datasheet - Page 37

• Manufacturer Part Number: LTC2431
• Description: (LTC2430 / LTC2431) 20-Bit No Latency Delta-Sigma ADCs
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
temperature) will produce a worst-case error of –180ppm
at a noise gain of 3, such as would be encountered in an
inverting gain of 2, to produce –10V from a 5V reference.
The error associated with the 10V excitation would be
–80ppm. Hence, overall reference error could be as high
as 130ppm, the average of the two.
Figure 45 shows a similar scheme to provide excitation
using resistor arrays to produce precise gain. The circuit
is configured to provide 10V and –5V excitation to the
bridge, producing a common mode voltage at the input to
the LTC2430/LTC2431 of 2.5V, maximizing the AC input
range for applications where induced 60Hz could reach
amplitudes up to 2V
The circuits in Figures 43 and 45 could be used where
multiple bridge circuits are involved and bridge output can
be multiplexed onto a single LTC2430/LTC2431, via an
inexpensive multiplexer such as the 74HC4052.
Figure 44 shows the use of an LTC2430/LTC2431 with a
differential multiplexer. This is an inexpensive multiplexer
that will contribute some error due to leakage if used
directly with the output from the bridge, or if resistors are
inserted as a protection mechanism from overvoltage.
Although the bridge output may be within the input range
U
RMS
.
U
Figure 44. Use a Differential Mulitplexer to Expand Channel Capability
TO OTHER
DEVICES
W
5V
U
12
14
15
11
1
5
2
4
74HC4052
8
16
9
10
of the A/D and multiplexer in normal operation, some
thought should be given to fault conditions that could
result in full excitation voltage at the inputs to the multi-
plexer or ADC. The use of amplification prior to the
multiplexer will largely eliminate errors associated with
channel leakage developing error voltages in the source
impedance.
Complete 20-Bit Data Acquistion System in 0.1 Inch
The LTC2430/LTC2431 provide 20-bit accuracy while
consuming a maximum of 300 A. The MS package of the
LTC2431 makes it especially attractive in applications
where very limited space is available. A complete 20-bit
data acquisition system in 0.1 inch
where the LTC2431 is powered by the LT1790 reference
family in an S6 package. A supply voltage from 0.25V
above the LT1790 output level to 20V enables the LT1790
to source up to 1mA and ensure the solid performance of
the LT2431.
The 3V, 3.3V, 4.096V and 5V versions of the LT1790 can
power the LTC2430/LTC2431 directly. Lower voltage ver-
sions will require a separate V
the LTC2430/LTC2431.
13
3
6
+
47 F
REF
REF
IN
IN
+
–
LTC2430/
LTC2431
+
–
GND
V
5V
CC
LTC2430/LTC2431
2431 F44
A0
A1
CC
supply of 2.7V to 5.5V for
2
is shown in Figure 46
37
24301f
2