Datasheet

ADA4084-1/ADA4084-2/ADA4084-4 Data Sheet
Rev. I | Page 32 of 36
LONG-TERM DRIFT
The stability of a precision signal path over its lifetime or
between calibration procedures is dependent on the long-term
stability of the analog components in the path, such as op amps,
references, and data converters. To help system designers
predict the long-term drift of circuits that use the ADA4084-1/
ADA4084-2/ADA4084-4, Analog Devices measured the offset
voltage of multiple units for 10,000 hours (more than 13 months)
using a high precision measurement system, including an
ultrastable oil bath. To replicate real-world system performance,
the devices under test (DUTs) were soldered onto an FR4 PCB
using a standard reflow profile (as defined in the JEDEC J-STD-
020D standard), as opposed to testing them in sockets. This
manner of testing is important because expansion and
contraction of the PCB can apply stress to the integrated circuit
(IC) package and contribute to shifts in the offset voltage.
The ADA4084-1/ADA4084-2/ADA4084-4 have extremely low
long-term drift, as shown in Figure 112. The red, blue, and
green traces show sample units. Note that the mean drift of the
ADA4084-1/ADA4084-2/ADA4084-4 over 10,000 hours is less
than 3 μV, or less than 3% of their maximum specified offset
voltage of 100 µV at room temperature.
CHANGE IN OFFSET VOLTAGE (µV)
08237-112
15
–15
10
5
0
–5
–10
TIME (Hours)
0
1000 2000 3000 4000 5000 6000 7000 8000 9000
10,000
V
SY
= 10V
27 UNITS
T
A
= 25°C
MEAN
MEAN PLUS ONE STANDARD DEVIATION
MEAN MINUS ONE STANDARD DEVIATION
SAMPLE 1
SAMPLE 2
SAMPLE 3
F
igure 112. Measured Long-Term Drift of the ADA4084-1/ADA4084-2/
ADA4084-4 Offset Voltage over 10,000 Hours
TEMPERATURE HYSTERESIS
In addition to stability over time as described in the Long-Term
Drift section, it is useful to know the temperature hysteresis,
that is, the stability vs. cycling of temperature. Hysteresis is an
important parameter because it tells the system designer how
closely the signal returns to its starting amplitude after the
ambient temperature changes and subsequent return to room
temperature. Figure 113 shows the change in input offset
voltage as the temperature cycles three times from room
temperature to +125°C to −40°C and back to room temperature.
The dotted line is an initial preconditioning cycle to eliminate
the original temperature-induced offset shift from exposure to
production solder reflow temperatures. In the three full cycles,
the offset hysteresis is typically only 4 μV, or 2% of its 200 µV
maximum offset voltage over the full operating temperature
range. The histogram in Figure 114 shows that the hysteresis is
larger when the device is cycled through only a half cycle, from
room temperature to 125°C and back to room temperature.
TEMPERATURE (°C)
CHANGE IN OFFSET VOLTAGE (µV)
V
SY
= 10V
08237-113
100
80
–100
–80
–40 –20 0 20 40 60 80 100 120
60
40
20
0
–20
–40
–60
PRECONDITION
CYCLE 1
CYCLE 2
CYCLE 3
F
igure 113. Change in Offset Voltage over Three Full Temperature Cycles
OFFSET VOLTAGE HYSTERESIS (µV)
NUMBER OF DEVICES
08237-114
0
–40 –32 –24 –18 –8 0 8 18 24 32 40
35
30
40
25
20
15
10
5
0
35
30
40
25
20
15
10
5
HALF CYCLE
FULL CYCLE
V
SY
= 10V
27 UNITS × 3 CYCLES
HALF CYCLE = +26°C, +125°C, +26°C
FULL CYCLE = +26°C, +125°C, +26°C, –40°C, +26°C
F
igure 114. Histogram Showing the Temperature Hysteresis of the Offset
Voltage over Three Full Cycles and over Three Half Cycles
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