LM2734ZEVAL National Semiconductor, LM2734ZEVAL Datasheet - Page 12

• Manufacturer Part Number: LM2734ZEVAL
• Description: BOARD EVALUATION LM2734Z
• Manufacturer: National Semiconductor

Specifications of LM2734ZEVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.8V
• Current - Output: 1A
• Voltage - Input: 3 ~ 20V
• Regulator Topology: Buck
• Frequency - Switching: 3MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM2734
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

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LLP Package
The LM2734Z is packaged in a Thin SOT23-6 package and
the 6–pin LLP. The LLP package has the same footprint as
the Thin SOT23-6, but is thermally superior due to the ex-
posed ground paddle on the bottom of the package.
R
than that of the Thin SOT23-6 package for a similar PCB con-
figuration (area, copper weight, thermal vias).
For certain high power applications, the PCB land may be
modified to a "dog bone" shape (see Figure 7). By increasing
the size of ground plane, and adding thermal vias, the R
for the application can be reduced.
θJA
of the LLP package is normally two to three times better
No Pullback LLP Configuration
FIGURE 7. Dog Bone
20130370
20130374
θJA
12
This example follows example 2, but uses the LLP package.
Using a standard National Semiconductor LLP-6 demonstra-
tion board, use Method 2 to determine R
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.
If the junction temperature is to be kept below 125°C, then the
ambient temperature cannot go above 73.2°C.
Design Example 4:
Package
V
V
I
V
Freq
I
I
V
T
T
R
IND
D
OUT
Q
BOOST
IN
OUT
D
BOOST
RISE
FALL
DSON
DCR
LLP-6
12.0V
3.3V
750mA
0.35V
3MHz
1.5mA
4mA
5V
8ns
8ns
400mΩ
75mΩ
30.3%
T
Operating Conditions
J
- (R
θJA
x P
P
P
P
P
P
P
P
P
P
LOSS
OUT
DIODE
IND
SWF
SWR
COND
Q
BOOST
LOSS
) = T
θJA
A
of the board. The
2.475W
523mW
56.25mW
108mW
108mW
68.2mW
18mW
20mW
902mW