SA57003 Datasheet, PDF (13/16 Pages) NXP Semiconductors – Five-output composite voltage regulator

Philips Semiconductors
Five-output composite voltage regulator
Product data
SA57003
generated heat. Heat dissipation must depend primarily on radiated
heat into the surrounding environment and the heat flow through the
leads into the printed circuit board. Some improvement can be
realized by allowing additional exposed copper on the circuit board
near the device to serve as heat absorbers and dissipaters for the
device.
The overall thermal resistance from junction to the surrounding
ambient of the package (R_th(j-a)) is made up of three series elements
and can be thought of as the total resistance of a series electrical
circuit. These elements are:
R_th(j-c) = Thermal resistance from Junction-to-Case
R_th(c-s) = Thermal resistance from Case-to-heat Sink
R_th(s-a) = Thermal resistance from heat Sink-to-Ambient
R_th(j-a) is based primarily on the package type and the size of the
silicon chip used in the device. The composition of package
materials plays an important part. High heat conductivity materials
produce reduced Junction-to-Case resistances.
R_th(c-s) value is based on the package type, heat sink interface, and
contact area of the device to the heat sink. The use of thermal
grease or an insulator will increase the transfer of heat from the
case to the heat sink.
R_th(s-a), which is thermal resistance from heat sink to the ambient, is
based on heat sink emissivity and airflow over the heat sink to carry
the heat away. The heat sink to ambient heat flow is dependent on
the ability of the surrounding ambient media to absorb the heat.
The total R_th(j-a) thermal resistance is expressed as:
R_th(j-a) = R_th(j-c) + R_th(c-s) + R_th(s-a)
The maximum power that a given package can handle is given by:
P_D
+
T_j(max) * T_amb
R_th(j*a)
DEFINITIONS
Line regulation is the change in output voltage caused by a change
in input line voltage. This parameter is measured using pulse
measurement techniques or under conditions of low power
dissipation so as to not significantly upset the thermal dynamics of
the device during test.
Load regulation is the change in output voltage caused by a
change in output load current for a constant device temperature.
Quiescent current is that current which flows to the ground pin of
the device when the device is operated with no load.
Ground current is that current which flows to the ground pin of the
device when the device is operated with output current flowing due
to an applied load. It is the measurement difference of input current
minus the output current.
Dropout voltage is the input/output differential at which the
regulator output no longer maintains regulation against further
reductions in input voltage. Measured when the output drops
100 mV below its nominal value (which is measured at 1.0 V
differential input/output), dropout voltage is affected by junction
temperature, load current and minimum input supply requirements.
Output noise voltage is the integrated output noise voltage
(RMS AC) specified over a frequency range and expressed in
nV/kHz or V_rms. It is measured at the output, with a constant load an
no input ripple.
Current limiting is internal device circuitry incorporated to limit the
output current of the device. This feature is incorporated in the
device to protect the device against output over current conditions or
output shorts to ground.
Thermal shutdown is internal device circuitry incorporated in the
device to shut down the device when the chip temperature reaches
a specified temperature. This feature protects the device from
excessive operating temperatures that would otherwise be
catastrophic to the device. Over heating can be created by
accidental output shorts.
Maximum power dissipation is the maximum total dissipation for
which the regulator will operate within specifications.
2003 Oct 13
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