amc7638 ADDtek Corp, amc7638 Datasheet - Page 6

• Manufacturer Part Number: amc7638
• Description: 450ma Dropout Regulator
• Manufacturer: ADDtek Corp

Copyright © 2007 ADDtek Corp.
The maximum power dissipation of a single-output regulator
Thermal consideration
overload conditions. However maximum junction temperature ratings should not be exceeded under continuous normal
load conditions. The thermal protection circuit of AMC7638 series will prevent the device from damage due to
excessive power dissipation. When the device temperature rises to approximately 150
off.
to control the junction temperature below 125
copper foil required. For multi-layered PCB, these layers can also be used as a heat sink. They can be connected with
several through hole vias.
Recommended figure of PCB area used as a heat sink.
P
PCB heat sink size (mm
D(MAX)
The AMC7638 series have internal power and thermal limiting circuitry designed to protect the device under
When power consumption is over about 775mW (SOT89 package, at T
The junction temperature is: T
If PC Board copper is going to be used as a heat sink, below table can be used to determine the appropriate size of
PCB θ
P
θ
θ
θ
= [(V
JT
SA
D
CS
: T hermal resistance from the junction to the mounting tab of the package.
: D issipated power.
: T hermal resistance from the mounting surface to ambient (thermal resistance of the heat sink).
SA
: T hermal resistance through the interface between the IC and the surface on which it is mounted.
(
(Top View)
O
IN(MAX)
(typically, θ
C /W )
V
I
I
V
- V
OUT(NOM)
Q
OUT(NOM)
IN(MAX)
2
= the quiescent current the regulator consumes at I
)
OUT(NOM)
CS
< 1.0
= the maximum input voltage
500
= the nominal output current, and
59
= the nominal output voltage
)] × I
J
O
= P
C /W)
OUT(NOM)
D
APPLICATION INFORMATION
(θ
1000
JT
45
+ θ
O
C.
+ V
(Bottom View)
CS
IN(MAX)
+ θ
SA
1500
38
) + T
6
× I
Q
A
through hole vias
2000
33
OUT(MAX)
A
=70
3000
O
27
C), additional heat sink is required
O
C, the regulator will be turned
4000
DD054_N -- MAY 2007
24
AMC7638
5000
21