Data Sheet ADR4520/ADR4525/ADR4530/ADR4533/ADR4540/ADR4550
Rev. 0 | Page 29 of 32
TERMINOLOGY
Dropout Voltage (VDO)
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.
VDO = (VIN − VOUT)min|IL = constant
Because the dropout voltage depends on the current passing
through the device, it is always specified for a given load current.
In series mode devices, the dropout voltage typically increases
proportionally to the load current (see Figure 6, Figure 21,
Figure 37, Figure 52, Figure 67, and Figure 82).
Temperature Coefficient (TCVOUT)
The temperature coefficient relates the change in the output
voltage to the change in the ambient temperature of the device, as
normalized by the output voltage at 25°C. This parameter is
determined by the box method, which is represented by the
following equation:
6
10
)()(
)},,({)},,({ ×
−×
−
=
132
OUT
321
OUT
321
OUT
OUT
TTTV
TTTVminTTTVmax
TCV
where:
TCVOUT is expressed in ppm/°C.
VOUT(Tx) is the output voltage at Temperature Tx.
T1 = −40°C.
T2 = +25°C.
T3 = +125°C.
This three-point method ensures that TCVOUT accurately portrays
the maximum difference between any of the three temperatures
at which the output voltage of the part is measured.
The TCVOUT for the ADR4520/ADR4525/ADR4530/ADR4533/
ADR4540/ADR4550 is fully tested over three temperatures:
−40°C, +25°C, and +125°C.
Thermally Induced Output Voltage Hysteresis (ΔVOUT_HYS)
Thermally induced output voltage hysteresis represents the
change in the 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.
6
25_
_25_
_10×
−
=∆
°
°
COUT
TCOUTCOUT
HYSOUT V
VV
V
[ppm]
where:
VOUT_25°C is the output voltage at 25°C.
VOUT_TC is the output voltage after temperature cycling.
Long-Term Stability (ΔVOUT_LTD)
Long-term stability refers to the shift in the output voltage at 60°C
after 1000 hours of operation in a 60°C environment. The ambient
temperature is kept at 60°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.
6
_10
)(
)()( ×
−
=∆
0
OUT
0
OUT
1
OUT
LTDOUT tV
tVtV
V
[ppm]
where:
VOUT(t0) is the VOUT at 60°C at Time 0.
VOUT(t1) is the VOUT at 60°C after 1000 hours of operation at 60°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 μV 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 μV per mA,
ppm per mA, or ohms of dc output resistance. This parameter
accounts for the effects of self-heating.
Solder Heat Resistance (SHR) Shift
SHR shift refers to the permanent shift in output voltage that is
induced by exposure to reflow soldering and is expressed in units
of ppm. This shift is caused by changes in the stress exhibited
on the die by the package materials when these materials are
exposed to high temperatures. This effect is more pronounced
in lead-free soldering processes due to higher reflow temperatures.