Datasheet

0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
-40 -20 0 20 40 60 80 100 120 140
AmbientTemperture(°C)
PowerDissipation(W)
TPS54262-Q1
www.ti.com SLVS996C –SEPTEMBER 2009–REVISED JUNE 2010
For device under operation at a given ambient temperature (T
A
), the junction temperature (T
J
) can be calculated
using Equation 30.
T
J
= T
A
+ (R
th
× P
Total
) (30) (30)
Therefore, the rise in junction temperature due to power dissipation is shown in Equation 31.
ΔT = T
J
– T
A
= (R
th
× P
Total
) (31) (31)
For a given maximum junction temperature (T
J-Max
), the maximum ambient temperature (T
A-Max
) in which the
device can operate is calculated using Equation 32.
T
A-Max
= T
J-Max
– (R
th
× P
Total
) (32) (32)
Where,
T
J
= junction temperature in °C
T
A
= ambient temperature in °C
R
th
= thermal resistance of package in W/°C
T
J-Max
= maximum junction temperature in °C
T
A-Max
= maximum ambient temperature in °C
There are several other factors that also affect the overall efficiency and power losses. Examples of such factors
are AC and DC losses in the inductor, voltage drop across the copper traces on PCB, power losses in the
flyback catch diode etc. Above discussion does not include such factors.
Figure 30. Power Dissipation vs Ambient Temperature
NOTE
The output current rating for the regulator may have to be derated for ambient
temperatures above 85°C. The derated value will depend on calculated worst-case power
dissipation and the thermal management implementation in the application.
Copyright © 2009–2010, Texas Instruments Incorporated Submit Documentation Feedback 25
Product Folder Link(s): TPS54262-Q1