LTC2433-1IMS Linear Technology, LTC2433-1IMS Datasheet - Page 26

• Manufacturer Part Number: LTC2433-1IMS
• Description: IC CONV A/D 16BIT DIFF 10-MSOP
• Manufacturer: Linear Technology

Specifications of LTC2433-1IMS

• Number Of Bits: 16
• Sampling Rate (per Second): 6.8
• 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)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LTC2433-1
APPLICATIO S I FOR ATIO
highest possible level of accuracy from this converter at
output data rates above 20 readings per second, the user
is advised to maximize the power supply voltage used and
to limit the maximum ambient operating temperature. In
certain circumstances, a reduction of the differential refer-
ence voltage may be beneficial.
Increasing Input Resolution by Reducing Reference
Voltage
The resolution of the LTC2433-1 can be increased by
reducing the reference voltage. It is often necessary to
amplify low level signals to increase the voltage resolution
of ADCs that cannot operate with a low reference voltage.
The LTC2433-1 can be used with reference voltages as low
as 100mV, corresponding to a 50mV input range with full
16-bit resolution. Reducing the reference voltage is func-
tionally equivalent to amplifying the input signal, however
no amplifier is required.
The LTC2433-1 has a 76 V LSB when used with a 5V
reference, however the thermal noise of the inputs is
1.45 V
reducing the reference voltage will increase the resolution
at the inputs as long as the LSB voltage is significantly
larger than 1.45 V
to a 8.7 V LSB, which is approximately the peak-to-peak
value of the 1.45 V
26
Figure 28. Integral Nonlinearity vs Output Data Rate
RMS
and is independent of reference voltage. Thus
22
20
18
16
14
12
10
0
V
V
V
V
–2.5V < V
F
O
CC
REF
REF
INCM
10
= EXTERNAL OSCILLATOR
OUTPUT DATA RATE (READINGS/sec)
= 5V
+
–
RMS
= 5V
= GND
20
RMS
= 2.5V
U
IN
30
< 2.5V
. A 570mV reference corresponds
input thermal noise. At this point,
40
U
50
60
70
W
80
90
2433 F28
100
U
the output code will be stable to 1LSB for a fixed input. As
the reference is decreased further, the measured noise will
approach 1.45 V
Figure 30 shows two methods of dividing down the
reference voltage to the LTC2433-1. Where absolute accu-
racy is required, a precision divider such as the Vishay
MPM series dividers in a SOT-23 package may be used. A
51:1 divider provides a 98mV reference to the LTC2433-1
from a 5V source. The resulting 49mV input range and
1.5 V LSB is suitable for thermocouple and 10mV full-
scale strain gauge measurements.
If high initial accuracy is not critical, a standard 2%
resistor array such as the Panasonic EXB series may be
used. Single package resistor arrays provide better tem-
perature stability than discrete resistors. An array of eight
resistors can be configured as shown to provide a 294mV
reference to the LTC2433-1 from a 5V source. The fully
differential property of the LTC2433-1 reference terminals
allow the reference voltage to be taken from four central
resistors in the network connected in parallel, minimizing
drift in the presence of thermal gradients. This is an ideal
reference for medium accuracy sensors such as silicon
micromachined pressure and force sensors. These de-
vices typically have accuracies on the order of 2% and full-
scale outputs of 50mV to 200mV.
–3
–6
–9
3
0
Figure 29. Offset Error vs Output
Data Rate and Reference Voltage
0
V
REF
V
V
F
T
O
CC
INCM
IN
A
10
= EXT OSC
= 25 C
RMS
OUTPUT DATA RATE (READINGS/SEC)
–
= 0V
= 5V
= GND
= 2.5V
20
.
30
40
50
V
REF
60
V
REF
= 2.5V
70
= 5V
80
90
24331 F29
100
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