LM22673EVAL National Semiconductor, LM22673EVAL Datasheet

BOARD EVALUATION FOR LM22673

LM22673EVAL

Manufacturer Part Number
LM22673EVAL
Description
BOARD EVALUATION FOR LM22673
Manufacturer
National Semiconductor
Series
SIMPLE SWITCHER®r
Datasheets

Specifications of LM22673EVAL

Main Purpose
DC/DC, Step Down
Outputs And Type
1, Non-Isolated
Voltage - Output
3.3V
Current - Output
3A
Voltage - Input
4.5 ~ 42V
Regulator Topology
Buck
Frequency - Switching
500kHz
Board Type
Fully Populated
Utilized Ic / Part
LM22673
Lead Free Status / RoHS Status
Not applicable / Not applicable
Power - Output
-
Other names
*LM22673EVAL
© 2010 National Semiconductor Corporation
LM22673 Evaluation Board
Introduction
The LM22673 evaluation board is designed to demonstrate
the capabilities of the LM22673 switching regulator. The
LM22673 evaluation board schematic shown in
configured to provide an output voltage of 3.3V up to 3A load
current with an input voltage range of 4.5V to 42V. Due to the
low R
mum duty-cycle limitations, the minimum input voltage of 4.5V
will only provide a 3.3V output voltage for load currents up to
500 mA. For load currents higher than 500 mA, an input volt-
age of 5.5V or higher is required. The typical operating fre-
quency is 500 kHz. The evaluation board is designed to
operate at ambient temperatures up to 50°C.
DS(ON)
of the integrated N-channel MOSFET and maxi-
300783
FIGURE 1. Evaluation Board Schematic
Figure 1
is
National Semiconductor
Application Note 1894
Frederik Dostal
September 16, 2010
The performance of the evaluation board is as follows:
Input Range: 4.5V to 42V
Output Voltage: 3.3V
Output Current Range: 0A to 3A
Frequency of Operation: 500 kHz
Board Size: 1.5 X 1.5 inches
Package: PSOP-8
At low input voltages between 4.5V and 6V, a minimum load
of approximately 5 mA may be required to reach a regulated
3.3V output voltage. See the LM22673 datasheet for more
details.
To aid in the design and evaluation of DC/DC buck converter
solutions based on the LM22673 switching regulator, the
evaluation board can be re-configured for different output
voltages.
The evaluation board is designed to highlight applications
with a small solution size. This implies that there will be a
tradeoff with the area of heat dissipation available. If this eval-
uation board is operated continuously at a full 3A load, it will
get hot. For higher output voltages than the pre-adjusted
3.3V, the total output power as well as the total power con-
version losses will increase. It is recommended to use a fan
or other source of air flow when evaluating the board at full
3A load or at output voltages greater than 3.3V. Typical eval-
uation board performance and characteristics curves are
shown in
layout.
Test points are provided to enable easy connection and mon-
itoring of critical signals. When performing over load or short
circuit tests, refer to the current limit section of the LM22673
datasheet to determine if the circuit is in safe operating mode.
For more information about device function and electrical
characteristics, refer to the LM22673 datasheet.
Figure 2
through
Figure
5.
30078301
Figure 6
shows the PCB
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LM22673EVAL Summary of contents

Page 1

... For load currents higher than 500 mA, an input volt- age of 5.5V or higher is required. The typical operating fre- quency is 500 kHz. The evaluation board is designed to operate at ambient temperatures up to 50°C. © 2010 National Semiconductor Corporation National Semiconductor Application Note 1894 Frederik Dostal ...

Page 2

... R3 is not populated on the evaluation board. This sets the current limit to the nominal current limit as specified in the LM22673 datasheet. TABLE 1. LM22673EVAL Bill of Materials for VOUT = 3.3V, Designed for 3A Output Current Ref # C1 C2 ...

Page 3

Performance Characteristics Unless otherwise specified 12V FIGURE 2. Start-Up Waveforms (Load Resistor = 1.1Ω) FIGURE 3. Operation 25°C. A 30078305 30078302 FIGURE 5. Overall Loop Gain and Phase (I 3 30078303 FIGURE 4. ...

Page 4

PCB Layout Diagram www.national.com 30078306 FIGURE 6. Top Layer 4 ...

Page 5

5 www.national.com ...

Page 6

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