Datasheet
XTR106
13
SBOS092A
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to the upper and lower sides of the bridge to keep the bridge
output within the 1.1V to 3.5V common-mode input range.
Bridge output is reduced so a preamplifier as shown may be
needed to reduce offset voltage and drift.
OTHER SENSOR TYPES
The XTR106 can be used with a wide variety of inputs. Its
high input impedance instrumentation amplifier is versatile
and can be configured for differential input voltages from
millivolts to a maximum of 2.4V full scale. The linear range
of the inputs is from 1.1V to 3.5V, referenced to the I
RET
terminal, pin 6. The linearization feature of the XTR106 can
be used with any sensor whose output is ratiometric with an
excitation voltage.
ERROR ANALYSIS
Table I shows how to calculate the effect various error
sources have on circuit accuracy. A sample error calculation
for a typical bridge sensor measurement circuit is shown
(5kΩ bridge, V
REF
= 5V, V
FS
= 50mV) is provided. The
results reveal the XTR106’s excellent accuracy, in this case
1.2% unadjusted. Adjusting gain and offset errors improves
circuit accuracy to 0.33%. Note that these are worst-case
errors; guaranteed maximum values were used in the calcu-
lations and all errors were assumed to be positive (additive).
The XTR106 achieves performance which is difficult to
obtain with discrete circuitry and requires less board space.
Bridge Impedance (R
B
)5kΩ Full Scale Input (V
FS
) 50mV
Ambient Temperature Range (∆T
A
)20°C Excitation Voltage (V
REF
)5V
Supply Voltage Change (∆V+) 5V Common-Mode Voltage Change (∆CM) 25mV (= V
FS
/2)
ERROR
(ppm of Full Scale)
TABLE I. Error Calculation.
SAMPLE ERROR CALCULATION
NOTE (1): All errors are min/max and referred to input, unless otherwise stated.
SAMPLE
ERROR SOURCE ERROR EQUATION ERROR CALCULATION UNADJ ADJUST
INPUT
Input Offset Voltage V
OS
/V
FS
• 10
6
200µV/50mV • 10
6
2000 0
vs Common-Mode CMRR • ∆CM/V
FS
• 10
6
50µV/V • 0.025V/50mV • 10
6
25 25
vs Power Supply (V
OS
vs V+) • (∆V+)/V
FS
• 10
6
3µV/V • 5V/50mV • 10
6
300 300
Input Bias Current CMRR • I
B
• (R
B
/2)/V
FS
• 10
6
50µV/V • 25nA • 2.5kΩ/50mV • 10
6
0.1 0
Input Offset Current I
OS
• R
B
/V
FS
• 10
6
3nA • 5kΩ/50mV • 10
6
300 0
Total Input Error 2625 325
EXCITATION
Voltage Reference Accuracy V
REF
Accuracy (%)/100% • 10
6
0.25%/100% • 10
6
2500 0
vs Supply (V
REF
vs V+) • (∆V+) • (V
FS
/V
REF
) 20ppm/V • 5V (50mV/5V) 1 1
Total Excitation Error 2501 1
GAIN
Span Span Error (%)/100% • 10
6
0.2%/100% • 10
6
2000 0
Nonlinearity Nonlinearity (%)/100% • 10
6
0.01%/100% • 10
6
100 100
Total Gain Error 2100 100
OUTPUT
Zero Output | I
ZERO
– 4mA |/16000µA • 10
6
25µA/16000µA • 10
6
1563 0
vs Supply (I
ZERO
vs V+) • (∆V+)/16000µA • 10
6
0.2µA/V • 5V/16000µA • 10
6
62.5 62.5
Total Output Error 1626 63
DRIFT (∆T
A
= 20
°
C)
Input Offset Voltage Drift • ∆T
A
/(V
FS
) • 10
6
1.5µV/°C • 20°C/(50mV) • 10
6
600 600
Input Offset Current (typical) Drift • ∆T
A
• R
B
/(V
FS
) • 10
6
5pA/°C • 20°C • 5kΩ/(50mV) • 10
6
10 10
Voltage Refrence Accuracy 35ppm/°C • 20°C 700 700
Span 225ppm/°C • 20°C 500 500
Zero Output Drift • ∆T
A
/16000µA • 10
6
0.9µA/°C • 20°C/16000µA • 10
6
1125 1125
Total Drift Error 2936 2936
NOISE (0.1Hz to 10Hz, typ)
Input Offset Voltage V
n
(p-p)/V
FS
• 10
6
0.6µV/50mV • 10
6
12 12
Zero Output I
ZERO
Noise/16000µA • 10
6
0.035µA/16000µA • 10
6
2.2 2.2
Thermal R
B
Noise
[√ 2 • √ (R
B
/2)/1kΩ • 4nV/√ Hz • √10Hz]/V
FS
• 10
6
[√ 2 • √ 2.5kΩ /1kΩ • 4nV/√Hz • √ 10Hz]/50mV • 10
6
0.6 0.6
Input Current Noise (i
n
• 40.8 • √2 • R
B
/2)/V
FS
•
10
6
(200fA/√Hz • 40.8 • √2 • 2.5kΩ)/50mV• 10
6
0.6 0.6
Total Noise Error 15 15
TOTAL ERROR: 11803 3340
1.18% 0.33%