GM6603 Datasheet, PDF (7/10 Pages) List of Unclassifed Manufacturers – 3.0A PRECISION LINEAR REGULATORS

GM6603
Output Voltage Sensing
The GM6603 series are three terminal regulators, so
they cannot provide true remote load sensing. Load
regulation is limited by the resistance of the conductors
connecting the regulator to the load. For best results
the GM6603 should be connected as shown in Figure
2.
V_IN
V_IN
V_OUT
GM6603-3.3
Conductor
Parasitic
R_{C Resistance}
GND
R_LOAD
(a) Fixed Version
The thermal characteristics of an IC depend four fac-
tors:
1. Maximum Ambient Temperature T_A (°C)
2. Power Dissipation P_D (Watts)
3. Maximum Junction Temperature T_J (°C)
4. Thermal Resistance Junction to ambient R_QJA
(°C/W)
These relationship of these four factors is expressed
by equation (1):
T_J = T_A + P_D X R_QJA
Maximum ambient temperature and power dissipa-
tion are determined by the design while the maxi-
mum junction temperature and thermal resistance
depend on the manufacturer and the package type.
V_IN
V_IN
V_OUT
GM6603-A
ADJ
(b) Adjustable Version
Conductor
Parasitic
R_{C Resistance}
R1
R_LOAD
R2
The maximum power dissipation for a regulator is ex-
pressed by equation (2):
P_D(max)={V_IN(max)-V_OUT(min)} I_OUT(max) + V_IN(max)I_Q
where:
V_IN(max) is the maximum input voltage,
V_OUT(min) is the minimum output voltage,
I_OUT(max) is the maximum output current
I_Q is the maximum quiescent current at I_OUT(max).
(a),(b)
FIGURE 2 Conductor Parasitic Resistance Effects are
Minimized by this Grounding Scheme For Fixed
and Adjustable Output Regulators
Calculating Power Dissipation and Heat
Sink Requirements
The GM6603 series precision linear regulators include
thermal shutdown and current limit circuitry to protect
the devices. However, high power regulators normally
operate at high junction temperatures so it is important
to calculate the power dissipation and junction temper-
atures accurately to be sure that you use and adequate
heat sink. The case is connected to V_OUT on the
GM6603, so electrical isolation may be required for
some applications. Thermal compound should always
be used with high current regulators like the GM6603.
A heat sink effectively increases the surface area of
the package to improve the flow of heat away from
the IC into the air. Each material in the heat flow
path between the IC and the environment has a ther-
mal resistance. Like series electrical resistances,
these resistances are summed to determine R_QJA,
the total thermal resistance between the junction
and the air. This is expressed by equation (3):
R_QJA = R_QJC + R_QCS + R_QSA
Where all of the following are in °C/W:
R_QJC is thermal resistance of junction to case,
R_QCS is thermal resistance of case to heat sink,
R_QSA is thermal resistance of heat sink to ambient
air
The value for R_QJA is calculated using equation (3)
and the result can be substituted in equation (1).
The value for R_QJC is 3.5°C/W for a given package
type based on an average die size. For a high cur-
rent regulator such as the GM6603 the majority of
the heat is generated in the power transistor section.
7