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© Semiconductor Components Industries, LLC, 2008
December, 2016 − Rev. 1
1 Publication Order Number:
AND8338/D
AND8338/D
How to Prevent Thermal
Issues with High Output
Current DC to DC
Converters in Portable
Applications
Introduction
As power demand in portable designs is more and more
important, designers must optimize full system efficiency in
order to save battery life and reduce power dissipation.
Energy losses study allows knowing thermal stakes. Due to
integration and miniaturization, junction temperature can
increase significantly which could lead to bad application
behaviors or in worst case to reduce components reliability.
Stand alones DC to DC converters are commonly used in
order to increase system efficiency. This document will
focus high output current switching regulators to
demonstrate that basic thermal skills are sufficient to avoid
any thermal issue. Tips and tricks to improve thermal
dissipation will be tackled in this document.
Power Dissipation Evaluation
Efficiency measurements directly lead to electrical power
dissipation results. It can be easily calculated on switching
converters using Equation 1.
P
DIP
+ V
OUT
I
OUT
ǒ
1
Eff
* 1
Ǔ
(eq. 1)
Worst environment cases allow designers to determine the
maximum power dissipation point. Following table could
help to determine worst cases of each parameter to get the
worst efficiency point.
Table 1. WORST ENVIRONMENT CASES
FOR DC-DC EFFICIENCY
Switching Converters
Ambient Temperature High
Input Voltage Minimum
Output Current Maximum
NCP1529 – 1 A DC to DC converter – will be used to
illustrate following application example which consists to
drive a core at 1.2 V; power demand will not exceed
900 mA.
Figure 1. NCP1529 Efficiency at V
IN
= 2.7 V, V
OUT
= 1.2 V, Temp = 85°C
APPLICATION NOTE
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