Datasheet

ADR3412/ADR3420/ADR3425/ADR3430/ADR3433/ADR3440/ADR3450
Rev. B | Page 18 of 24
TERMINOLOGY
Dropout Voltage (V
DO
)
Dropout voltage, sometimes referred to as supply voltage
headroom or supply-output voltage differential, is defined as
the minimum voltage differential between the input and output
such that the output voltage is maintained to within 0.1%
accuracy.
V
DO
= (V
IN
− V
OUT
)
min
| I
L
= constant
Because the dropout voltage depends upon the current passing
through the device, it is always specified for a given load current.
In series-mode devices, dropout voltage typically increases
proportionally to load current (see Figure 8 and Figure 14).
Temperature Coefficient (TCV
OUT
)
The temperature coefficient relates the change in output voltage
to the change in ambient temperature of the device, as normalized
by the output voltage at 25°C. This parameter is expressed in
ppm/°C and can be determined by the following equation:
]/[10
)()(
)},,(min{)},,(max{
6
132
321321
Cppm
TTTV
TTTVTTTV
TCV
OUT
OUTOUT
OUT
°
×
−×
−
=
(1)
where:
V
OUT
(T) is the output voltage at Temperature T.
T
1
= −40°C.
T
2
= +25°C.
T
3
= +125°C.
This three-point method ensures that TCV
OUT
accurately
portrays the maximum difference between any of the three
temperatures at which the output voltage of the part is
measured.
The TCV
OUT
for the ADR3412/ADR3425/ADR3430/ADR3433/
ADR3440/ADR3450 is guaranteed via statistical means. This is
accomplished by recording output voltage data for a large
number of units over temperature, computing TCV
OUT
for each
individual device via Equation 1, then defining the maximum
TCV
OUT
limits as the mean TCV
OUT
for all devices extended by
six standard deviations (6σ).
Thermally Induced Output Voltage Hysteresis (ΔV
OUT_HYS
)
Thermally induced output voltage hysteresis represents the
change in output voltage after the device is exposed to a
specified temperature cycle. This is expressed as either a shift in
voltage or a difference in ppm from the nominal output.
TCOUTOUTHYSOUT
VCVV
__
)25( −°
=
Δ
[V]
6
_
_
10
)25(
)25(
×
°
−°
=Δ
CV
VCV
V
OUT
TCOUTOUT
HYSOUT
[ppm]
where:
V
OUT
(25°C) is the output voltage at 25°C.
V
OUT_TC
is the output voltage after temperature cycling.
Long-Term Stability (ΔV
OUT_LTD
)
Long-term stability refers to the shift in output voltage at 50°C
after 1000 hours of operation in a 50°C environment. Ambient
temperature is kept at 50°C to ensure that the temperature
chamber does not switch randomly between heating and cooling,
which can cause instability over the 1000 hour measurement.
This is also expressed as either a shift in voltage or a difference
in ppm from the nominal output.
)()(
01
_
tVtVV
OUTOUTLTDOUT
−=Δ
[V]
6
0
01
_
10
)(
)()(
×
−
=Δ
tV
tVtV
V
OUT
OUTOUT
LTDOUT
[ppm]
where:
V
OUT
(t
0
) is the V
OUT
at 50°C at Time 0.
V
OUT
(t
1
) is the V
OUT
at 50°C after 1000 hours of operation
at 50°C.
Line Regulation
Line regulation refers to the change in output voltage in response
to a given change in input voltage and is expressed in percent
per volt, ppm per volt, or V per volt change in input voltage.
This parameter accounts for the effects of self-heating.
Load Regulation
Load regulation refers to the change in output voltage in
response to a given change in load current and is expressed in
V per mA, ppm per mA, or ohms of dc output resistance. This
parameter accounts for the effects of self-heating.
Solder Heat Resistance (SHR) Drift
SHR drift refers to the permanent shift in output voltage
induced by exposure to reflow soldering, expressed in units of
ppm. This is caused by changes in the stress exhibited upon the
die by the package materials when exposed to high tempera-
tures. This effect is more pronounced in lead-free soldering
processes due to higher reflow temperatures.