AS1374
Datasheet - Application Information
Figure 28. Steady State Heat Flow Equivalent Circuit
Junction
TJ°C
Package
TC°C
PCB/Heatsink
TS°C
Ambient
TA°C
RJC
RCS
RSA
Chip
Power
Total Thermal Path Resistance:
RJA = RJC + RCS + RSA
(EQ 6)
(EQ 7)
Junction Temperature (TJ ºC) is determined by:
TJ = (PD(MAX) x RJA) + TAMB ºC
9.5 Explanation of Steady State Specifications
9.5.1 Line Regulation
Line regulation is defined as the change in output voltage when the input (or line) voltage is changed by a known quantity. It is a measure of the
regulator’s ability to maintain a constant output voltage when the input voltage changes. Line regulation is a measure of the DC open loop gain
of the error amplifier. More generally:
VOUT
-----------------
Line Regulation =
and is a pure number
(EQ 8)
VIN
In practise, line regulation is referred to the regulator output voltage in terms of % / VOUT. This is particularly useful when the same regulator is
available with numerous output voltage trim options.
VOUT
----------------- -------------
100
VOUT
Line Regulation =
% / V
(EQ 9)
VIN
9.5.2 Load Regulation
Load regulation is defined as the change of the output voltage when the load current is changed by a known quantity. It is a measure of the
regulator’s ability to maintain a constant output voltage when the load changes. Load regulation is a measure of the DC closed loop output
resistance of the regulator. More generally:
VOUT
-----------------
Load Regulation =
and is units of ohms ()
(EQ 10)
IOUT
In practise, load regulation is referred to the regulator output voltage in terms of % / mA. This is particularly useful when the same regulator is
available with numerous output voltage trim options.
VOUT
100
----------------- -------------
Load Regulation =
% / mA
(EQ 11)
IOUT VOUT
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