AN1729: ISL28133 Long Term Drift

Application Note 1729
Author: Bob Pospisil
ISL28133 Long Term Drift
Figure 2 shows a plot of daily VOS drift measurements of 30
individual ISL28133 amplifiers over a continuous 572 day
period at +25°C. The 30 units were connected in a gain of 10k
(see Figure 3), mounted on a single PC board and kept at room
temperature. The 30 amplifier outputs were measured daily by
a DVM and scanner under computer control. The daily VOS
measurements were subtracted from the initial VOS value to
calculate the VOS shift from zero-hour. The test board was
powered from a UPS to maintain uninterrupted power to the
test units. Three instances of lost measurement data ranging
from 2 days to 2 weeks due to power loss to the measurement
scanner were detected, and data was interpolated.
100k
+2.5V
10
10
VOUT
+
1k
-2.5V
100k
ACL = 10kV/V
FIGURE 1. LONG TERM DRIFT TEST CIRCUIT
The change in amplifier VOS over the 572 day period for all 30
amplifiers (see Figure 2) was less than ±100nV, and no clear
VOS long term drift trend was evident in the data. The excellent
long term drift performance is a result of the chopper
amplifier’s ability to measure and correct VOS errors, leaving
only the VOS error contribution due to changes in the long term
stability of the external components.
1.0
0.8
0.6
VOS (µV)
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
450
480
510
540
570
600
450
480
510
540
570
600
TIME (DAYS)
FIGURE 2. LONG TERM DRIFT (V OS vs TIME) FOR 30 UNITS
1.0
0.8
0.6
VOS (µV)
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0
30
60
90
120
150
180
210
240
270
300
330
360
390
420
TIME (DAYS)
FIGURE 3. LONG TERM DRIFT (VOS vs TIME) FOR A SINGLE UNIT
March 5, 2012
AN1729.0
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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