GM6603 ETC2 [List of Unclassifed Manufacturers], GM6603 Datasheet - Page 7

• Manufacturer Part Number: GM6603
• Description: 3.0A PRECISION LINEAR REGULATORS
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

(a) Fixed Version
(b) Adjustable Version
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.
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
GM6603, so electrical isolation may be required for
some applications. Thermal compound should always
be used with high current regulators like the GM6603.
FIGURE 2
V
V
IN
IN
Minimized by this Grounding Scheme For Fixed
V
(a),(b)
V
and Adjustable Output Regulators
IN
IN
GM6603-3.3
Conductor Parasitic Resistance Effects are
GM6603-A
GND
ADJ
V
V
OUT
OUT
R2
R1
R
R
C
C
Conductor
Parasitic
Resistance
Conductor
Parasitic
Resistance
OUT
R
R
LOAD
LOAD
on the
The thermal characteristics of an IC depend four fac-
tors:
1. Maximum Ambient Temperature T (°C)
2. Power Dissipation P (Watts)
3. Maximum Junction Temperature T (°C)
4. Thermal Resistance Junction to ambient R
These relationship of these four factors is expressed
by equation (1):
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.
The maximum power dissipation for a regulator is ex-
pressed by equation (2):
where:
V
V
I
I is the maximum quiescent current at I
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
the total thermal resistance between the junction
and the air. This is expressed by equation (3):
Where all of the following are in °C/W:
R
R
R
air
The value for R
and the result can be substituted in equation (1).
The value for R
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.
OUT(max)
Q
IN(max)
OUT(min)
QJC
QCS
QSA
(°C/W)
P
is thermal resistance of junction to case,
is thermal resistance of case to heat sink,
is thermal resistance of heat sink to ambient
D(max)
is the maximum input voltage,
is the maximum output current
is the minimum output voltage,
R
={V
Q
T = T + P X R
JA
J
IN(max)
= R
QJA
QJC
Q
is 3.5°C/W for a given package
is calculated using equation (3)
A
JC
-V
D
OUT(min)
+ R
D
Q
CS
} I
+ R
OUT(max)
Q
Q
JA
SA
A
J
+ V
OUT(max)
IN(max) Q
Q
GM6603
JA
.
I
QJA
,
7