Datasheet

ADR420/ADR421/ADR423/ADR425 Data Sheet
Rev. J | Page 16 of 24
TERMINOLOGY
Temperature Coefficient
The change of output voltage over the operating temperature
range is normalized by the output voltage at 25°C, and
expressed in ppm/°C as

 


6
10/ 



12
OUT
1
OUT
2
OUT
OUT
TTC25V
TVTV
CppmTCV
where:
V
OUT
(25°C) = V
OUT
at 25°C.
V
OUT
(T
1
) = V
OUT
at Temperature 1.
V
OUT
(T
2
) = V
OUT
at Temperature 2.
Line Regulation
The change in output voltage due to a specified change in input
voltage. It includes the effects of self-heating. Line regulation is
expressed in either percent per volt, parts per million per volt,
or microvolts per volt change in input voltage.
Load Regulation
The change in output voltage due to a specified change in load
current. It includes the effects of self-heating. Load regulation is
expressed in either microvolts per milliampere, parts per
million per milliampere, or ohms of dc output resistance.
Long-Term Stability
Typical shift of output voltage at 25°C on a sample of parts
subjected to operation life test of 1000 hours at 125°C.


1
OUT
0
OUTOUT
tVtVV 





6
10


0
OUT
1
OUT
0
OUT
OUT
tV
tVtV
ppmV
where:
V
OUT
(t
0
) = V
OUT
at 25°C at Time 0.
V
OUT
(t
1
) = V
OUT
at 25°C after 1000 hours operation at 125°C.
Thermal Hysteresis
The change of output voltage after the device is cycled through
temperatures from +25°C to −40°C to +125°C and back to
+25°C. This is a typical value from a sample of parts put
through such a cycle.


TCOUTOUTHYSOUT
VC25VV
__






6
_
_
10



C25V
VC25V
ppmV
OUT
TCOUTOUT
HYSOUT
where:
V
OUT
(25°C) = V
OUT
at 25°C.
V
OUT_TC
= V
OUT
at 25°C after temperature cycle at +25°C to
−40°C to +125°C and back to +25°C.
Input Capacitor
Input capacitors are not required on the ADR42x. There is
no limit for the value of the capacitor used on the input, but a
1 µF to 10 µF capacitor on the input improves transient response
in applications where the supply suddenly changes. An addi-
tional 0.1 µF capacitor in parallel also helps to reduce noise
from the supply.
Output Capacitor
The ADR42x do not need output capacitors for stability under
any load condition. An output capacitor, typically 0.1 µF, filters
out any low level noise voltage and does not affect the operation
of the part. On the other hand, the load transient response can
be improved with an additional 1 F to 10 F output capacitor
in parallel. A capacitor here acts as a source of stored energy for
sudden increase in load current. The only parameter that
degrades by adding an output capacitor is the turn-on time,
which depends on the size of the selected capacitor.