LTC2411IMS#PBF Linear Technology, LTC2411IMS#PBF Datasheet - Page 34

• Manufacturer Part Number: LTC2411IMS#PBF
• Description: IC A/D CONV 24BIT MICRPWR 10MSOP
• Manufacturer: Linear Technology

Specifications of LTC2411IMS#PBF

• Number Of Bits: 24
• Sampling Rate (per Second): 7.5
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 2
• Power Dissipation (max): 1mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
• Number Of Elements: 1
• Resolution: 24Bit
• Architecture: Delta-Sigma
• Sample Rate: 0.008KSPS
• Input Polarity: Bipolar
• Input Type: Voltage
• Rated Input Volt: ±2.75V
• Differential Input: Yes
• Power Supply Requirement: Single
• Single Supply Voltage (typ): 3.3/5V
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (typ): Not RequiredV
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Integral Nonlinearity Error: 14ppm of Vref
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 10
• Package Type: MSOP
• Input Signal Type: Differential
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIO S I FOR ATIO
LTC2411/LTC2411-1
the sensor largely eliminates the need for protection
devices, RFI suppression and wiring. The LTC2411/
LTC2411-1 exhibit extremely low temperature dependent
drift. As a result, exposure to external ambient tempera-
ture ranges does not compromise performance. The in-
corporation of any amplification considerably complicates
thermal stability, as input offset voltages and currents,
temperature coefficient of gain settling resistors all be-
come factors.
The circuit in Figure 41 shows an example of a simple
amplification scheme. This example produces a differen-
tial output with a common mode voltage of 2.5V, as
determined by the bridge. The use of a true three amplifier
instrumentation amplifier is not necessary, as the LTC2411/
LTC2411-1 have common mode rejection far beyond that
of most amplifiers. The LTC1051 is a dual autozero ampli-
fier that can be used to produce a gain of 30 before its input
referred noise dominates the LTC2411/LTC2411-1 noise.
This example shows a gain of 34, that is determined by a
feedback network built using a resistor array containing
eight individual resistors. The resistors are organized to
optimize temperature tracking in the presence of thermal
gradients. The second LTC1051 buffers the low noise
34
BRIDGE
350
U
RN1
RN1 = 5k 8 RESISTOR ARRAY
U1A, U1B, U2A, U2B = 1/2 LTC1051
U
16
1
Figure 41. Using Autozero Amplifiers to Reduce Input Referred Noise
6
3
2
6
5
W
11
–
+
+
–
15
2
U1A
U1B
5V
4
7
8
10
14
0.1 F
3
U
1
7
8
9
13
4
5
input stage from the transient load steps produced during
conversion.
The gain stability and accuracy of this approach is very
good, due to a statistical improvement in resistor match-
ing due to individual error contribution being reduced. A
gain of 34 may seem low, when compared to common
practice in earlier generations of load-cell interfaces, how-
ever the accuracy of the LTC2411/LTC2411-1 changes the
rationale. Achieving high gain accuracy and linearity at
higher gains may prove difficult, while providing little
benefit in terms of noise reduction.
At a gain of 100, the gain error that could result from
typical open-loop gain of 160dB is –1ppm, however,
worst-case is at the minimum gain of 116dB, giving a gain
error of –158ppm. Worst-case gain error at a gain of 34,
is –54ppm. The use of the LTC1051A reduces the worst-
case gain error to –33ppm. The advantage of gain higher
than 34, then becomes dubious, as the input referred
noise sees little improvement
tially compromised.
1
0.048 V
Input referred noise for A
12
RMS
.
2
3
6
5
–
+
–
+
U2A
U2B
5V
V
4
8
= 34 is approximately 0.05 V
0.1 F
1
7
2
3
4
5
1
REF
REF
IN
IN
and gain accuracy is poten-
LTC2411-1
+
–
LTC2411/
+
–
GND
RMS
V
CC
6
, whereas at a gain of 50, it would be
1
SDO
SCK
CS
F
5V
0.1 F
O
REF
8
9
7
10
2411 F41