Datasheet

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SWN
C3
10 µF
L1
10 µH
R1
R2
VBAT
VOUT
LDOIN
LDOSENSE
LDOOUT
R7 R8
C6
2.2 µF
C4
100 µF
U1
LBO
PGOOD
PGND
LBI
SYNC
EN
LDOEN
GND
TPS61120PW
List of Components:
U1 = TPS61120PW
L1 = Sumida CDRH73–100
C3, C5, C6 = X7R/X5R Ceramic
C4 = Low ESR Tantalum
D1 = On-Semiconductor MBR0520
V
CC
Control
Outputs
D1
USB Input
4.2 V...5.5 V
FB
3.3 V System Supply
R5
R4
1.022 MΩ
180 kΩ
R3
1 MΩ
180 kΩ
R6
SWP
THERMAL INFORMATION
P
D(MAX)

T
J(MAX)
 T
A
R
JA

150 °C  85°C
155 °CW
 420 mW
(10)
TPS61120
TPS61122, TPS61121
SLVS427C – JUNE 2002 – REVISED APRIL 2004
APPLICATION INFORMATION (continued)
Figure 30. Dual Input Power Supply Solution
Implementation of integrated circuits in low-profile and fine-pitch surface-mount packages typically requires
special attention to power dissipation. Many system-dependent issues such as thermal coupling, airflow, added
heat sinks and convection surfaces, and the presence of other heat-generating components affect the
power-dissipation limits of a given component.
Three basic approaches for enhancing thermal performance are listed below.
• Improving the power dissipation capability of the PCB design
• Improving the thermal coupling of the component to the PCB
• Introducing airflow in the system
The maximum junction temperature (T
J
) of the TPS6112x devices is 150 °C. The thermal resistance of the 16-pin
TSSOP package (PW) is R
ΘJA
= 155 °C/W. The 16-pin QFN PowerPAD package (RSA) has a thermal resistance
of R
ΘJA
= 38.1 °C/W, if the PowerPAD is soldered and the board layout is optimized. Specified regulator
operation is assured to a maximum ambient temperature T
A
of 85°C. Therefore, the maximum power dissipation
is about 420 mW for the TSSOP (PW) package and 1700 mW for the QFN (RSA) package; See Equation 10 .
More power can be dissipated if the maximum ambient temperature of the application is lower.
If designing for a lower junction temperature of 125°C, which is recommended, maximum heat dissipation is
lower. Using the above Equation 10 results in 1050 mW power dissipation for the RSA package and 260mW for
the PW package.
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