NSC LMZ142033A

National Semiconductor
Application Note 2032
Alan Martin
January 22, 2010
Description
Demo Board Features
The LMZ14203 SIMPLE SWITCHER power module is a complete, easy to use step-down DC-DC solution capable of
driving up to 3A load. The LMZ14203 is available in an innovative, easy to use package that enhances thermal performance and allows for hand or machine soldering.
The LMZ14203 demo board can accept an input voltage rail
between 8V and 42V and deliver an adjustable and highly
accurate output voltage as low as 0.8V. The LMZ14203 only
requires three external resistors and four external capacitors
to complete the power solution. The LMZ14203 is a reliable
and robust solution with the following protection features:
thermal shutdown, input under-voltage lockout, output overvoltage protection, short-circuit protection, output current limit, and allows startup into a pre-biased output. A single resistor
adjusts switching frequency up to 1 MHz.
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Packaging Highlights
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Power input voltage range 6V-42V
UVLO programmed at 8V
Adjustable output voltage range 0.8V to 6V
Up to 3A output current
Integrated shielded inductor in module
Efficiency up to 92%
All ceramic capacitor design
No loop compensation required
Starts into pre-biased loads
Short circuit protection
Thermal Shutdown
Only 9 external passives plus module
Max 78°C ambient at full load
2 layer low cost assembly
Typical Applications
7 lead module package (Similar to TO-263)
Single exposed die attach pad for enhanced thermal
performance
10.2 x 13.8 x 4.6 mm module package
High power density
1.7” x 2.3” reduced size demo board form factor
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Point of load conversions from 12V and 24V input rail
Space constrained applications
Industrial controls
Telecom
Networking equipment
© 2010 National Semiconductor Corporation
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Back View
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Front View
LMZ14203 3A Demo Board SIMPLE SWITCHER® Power Module Quick Start Guide
LMZ14203 3A Demo Board
SIMPLE SWITCHER® Power
Module Quick Start Guide
AN-2032
Absolute Maximum Module Ratings
Demo Board Operating Ratings
VIN, RON to GND -0.3V to 47
VIN
6V to 42V
EN, FB, SS to
GND
VOUT (Default
setting)
3.3V
IOUT
0A to 3A
-0.3V to 7V
Module Operating Ratings
VIN
EN (Input on demo 0V to 42V
board post)
6V to 42V
EN (Input on pin 3 0V to 6.5V
module pin)
UVLO setting on
ENable input
8V
Junction
Temperature
Range (Tj)
Soft-start time
2.2 mSec
Operating
Temperature
Range (Tj)
- 40C to +78C (at
full 3A load)
- 40C to +125C
Demo Board Schematic
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Demo Board Bill of Materials
Ref Des
Description
Case
RON
61.9 kohm 1%
resistor
603
RENT
68.1 kohm 1%
resistor
603
RENB
11.8 kohm 1%
resistor
603
RFBT
3.32 kohm 1%
resistor
603
RFBB
1.07 kohm 1%
resistor
603
CFF
0.022 uF 50V X7R 603
ceramic capacitor
CSS
0.022 uF 50V X7R 603
ceramic capacitor
CIN1
10 uF 50V X5R
1210
ceramic capacitor
UMK325BJ106M
M-T
CO1
1.0 uF 50V X7R
1206
ceramic capacitor
UMK316B7105KL
-T
CO2
100 uF 6.3V X5R 1210
ceramic capacitor
JMK325BJ107M
M-T
U1
LMZ14203
SIMPLE
SWITCHER
Power Module
LMZ14203TZADJ
TOPMOD
Manufacturer
Part Number
Alternate resistor values for alternative output voltages
VOUT
RFBT
RFBB
RON
6
2.49k
3.83k
124k
5
5.62k
1.07k
100k
3.3
3.32k
1.07k
61.9k
2.5
2.26k
1.07k
47.5k
1.8
1.87k
1.50k
32.4k
1.5
1.00k
1.13k
28.0k
1.2
4.22k
8.45k
22.6k
0.8
0.0K
39.2k
24.9k
Quiescent current: If the Enable post is disconnected, the
module will be disabled and about 20 uA of supply current will
flow from Vin to ground while in the disabled mode. With the
enable input connected to Vin via the 68.1K/11.8K divider
there will be about 1.5 mA of no-load quiescent current into
the Vin input. Additional current flows into the enable divider
string.
Demo Board Hookup
VOUT Connect the load to VOUT and one of the GND posts.
The module can source up to a 3A load current.
VIN : Connect Vin to a positive voltage in the 8 to 42V range.
Connect the negative terminal of the source supply to one of
the posts labeled GND.
En: The Enable input post is configured for direct connection
to the Vin post. The on-board resistive voltage divider is chosen such that when connected to 42V that the enable input at
pin 3 of the module will not exceed 6.5V. With the chosen
resistor values this results in an under voltage lockout level of
8 V input. The top enable resistor is RENT (aka REN1) and
the bottom enable resistor is RENB (aka REN2). The bottom
enable resistor may have a location for a shunt zener clamp
(Labeled D1 OPT in the silkscreen - Included only in the later
revisions of the assembly.)
Demo Board Passive Components
Soft-start capacitor The soft-start capacitor controls the rise
time of the output voltage when power is first applied and following the clearing of a fault mode.
Feedback dividerRegulator output voltage is programmed
though the selection of the two resistors, RFBT ( aka RFB1)
and RFB (aka RFB2) A feed forward capacitor (CFF) is located in parallel with the upper feedback divider resistor. This
capacitor improves the step response to abrupt changes in
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load current. Refer to the table above when modifying the
board for a different output voltage. Resistor values shown
will minimize error in output voltage setting.
RON Resistor: The primary function of the RON resistor is to
set the On-Time interval of the internal control section switching cycle. The secondary function of the RON resistor is to
create a nearly constant operating frequency over the input
operating voltage range. If the output voltage of the regulator
is changed by adjusting the feedback divider then it is generally required that the RON resistor value also be changed in
order to maintain the same operating frequency.
Cout A parallel connection of a 1uF 50V and a 100uF 6.3V
multilayer ceramic are used for the output capacitor. Locations are provided on the PCB assembly for experimenting
with additional output capacitors. Some recommended values
are shown on the schematic as “DNS” and labeled in the PCB
silkscreen as “OPT”.
CinA 10 uF 50V multilayer ceramic is connected as the input
filter. Locations are provided on the PCB assembly for experimenting with additional input capacitors. Some recommended values are shown on the schematic as “DNS” and labeled
in the PCB silkscreen as “OPT”.
Performance Characteristics
Efficiency 24V [email protected] 25°C
Dissipation, 24V [email protected] 25°C
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Line and Load Regulation @ 25°C
Transient Response
24VIN 3.3Vo 0.6A to 3A Step
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Notes
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LMZ14203 3A Demo Board SIMPLE SWITCHER® Power Module Quick Start Guide
Notes
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