Datasheet

R
T
JA
a =
165
o
C - 113
o
C
322 mW
= 161
o
C/W
6P
COND
+ P
SWF
+ P
SWR
+ P
Q
+ P
BOOST
= P
INTERNAL
P
INTERNAL
= 322 mW
LM2734Z
SNVS334E –JANUARY 2005–REVISED APRIL 2013 www.ti.com
(48)
This example follows example 2, but uses the WSON package. Using a standard Texas Instruments WSON-6
demonstration board, use Method 2 to determine R
θJA
of the board. The four layer PCB is constructed using FR4
with 1/2oz copper traces. The copper ground plane is on the bottom layer. The ground plane is accessed by four
vias. The board measures 2.5cm x 3cm. It was placed in an oven with no forced airflow.
The ambient temperature was raised to 113°C, and at that temperature, the device went into thermal shutdown.
(49)
If the junction temperature is to be kept below 125°C, then the ambient temperature cannot go above 73.2°C.
T
J
- (R
θJA
x P
LOSS
) = T
A
(50)
Package Selection
To determine which package you should use for your specific application, variables need to be known before you
can determine the appropriate package to use.
1. Maximum ambient system temperature
2. Internal LM2734Z power losses
3. Maximum junction temperature desired
4. R
θJA
of the specific application, or R
θJC
(WSON or Thin SOT-6)
The junction temperature must be less than 125°C for the worst-case scenario.
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