MAXM17545 in 3.3V Output-Voltage Application

MAXM17545 in 3.3V Output-Voltage Application
MAXM17545 3.3V Output
Evaluation Kit
General Description
The MAXM17545 evaluation kit (EV kit) is a demonstration
circuit of MAXM17545 high-voltage, high-efficiency, current
mode scheme, synchronous step-down DC-DC switching
power module. The EV kit is designed for a 3.3V output
and delivers up to 1.7A load current from a wide inputvoltage range of 4.5V to 42V. The EV kit switches at an
optimal 400kHz switching frequency to allow the use of
small component-sizes, helping to minimize solution-size
while maintaining high-performance. The EV kit provides
a precision-enable input, an open-drain RESET output
signal, and external frequency synchronization to provide
a simple and reliable startup sequence and eliminate beat
frequency between regulators. The EV kit also includes
optional component footprints to program different output
voltages, an adjustable input undervoltage-lockout, and a
soft-start time to control inrush current during startup. The
MAXM17545 IC data sheet provides a complete description of the part that should be read in conjunction with this
data sheet prior to modifying the demo circuit.
Ordering Information appears at end of data sheet.
19-7617; Rev 0; 5/15
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
Features
●● Highly Integrated Solution with Integrated Shield Inductor
●● Wide 4.5V to 42V Input Range
●● Preset 3.3V Output with a Fixed Resistor-Divider on
FB (Feedback Pin)
●● Programmable Output-Voltage Feature (0.9V to 12V)
●● Up to 1.7A Output Current
●● High 91.2% Efficiency (VIN = 12V, VOUT = 3.3V at 0.73A)
●● 400kHz Switching Frequency
●● Enable/UVLO Input, Resistor-Programmable UVLO
Threshold
●● Adjustable Soft-Start Time
●● Selectable PWM, PFM, or DCM Mode
●● Open-Drain RESET Output
●● External Frequency Synchronization
●● Overcurrent and Overtemperature Protection
●● Low-Profile, Surface-Mount Components
●● Lead(Pb)-Free and RoHS Compliant
●● Fully Assembled and Tested
MAXM17545 3.3V Output
Evaluation Kit
Quick Start
Recommended Equipment
●●
●●
●●
●●
●●
MAXM17545 EV kit
4.5V to 42V DC power supply (VIN)
Dummy load capable of sinking 1.7A
Digital voltmeter (DVM)
100MHz dual-trace oscilloscope
Procedure
The EV kit is fully assembled and tested. Follow the steps
below to verify board operation. Caution: Do not turn on
the power supply until all connections are completed.
1) Set the power supply at a voltage between 4.5V and
42V. Disable the power supply.
2) Connect the positive and negative terminals of the
power supply to IN and PGND PCB pads, respectively.
3) Connect the positive and negative terminals of the
1.7A load to OUT and PGND2 PCB pads, respectively,
and set the load to 0A.
4) Connect the DVM across the OUT PCB pad and the
PGND2 PCB pad.
5) Verify that no shunts are installed across pins 1-2 on
jumper JU1 to enable UVLO (see Table 1 for details).
6) Verify that a shunt is installed across JU3 to disable
the external synchronization (see Table 3 for details).
7) Verify that a shunt is installed across JU2 to enable
PWM mode (see Table 2 for details).
8) Enable the input power supply.
9) Verify the DVM displays 3.3V.
10) Increase the load up to 1.7A to verify the DVM
continues displaying 3.3V.
Detailed Description of Hardware
The EV kit is a proven circuit to demonstrate the highvoltage, high-efficiency, and compact solution-size of the
synchronous step-down DC-DC power module. The
output voltage is preset for 3.3V to operate from 4.5V to
42V and provides up to 1.7A load current. The optimal frequency is set at 400kHz to maximize efficiency and minimize
component size. The EV kit includes JU1 to enable/disable
UVLO of the device, JU2 to configure in PWM, PFM, or
DCM mode to improve light-load efficiency, and JU3 to
enable/disable external clock synchronize (SYNC). The
RESET PCB pad is also available for monitoring output
voltage regulation to enable/disable the application circuit
of the load. The electrolytic capacitor (C8) is required only
when the VIN power supply is situated far from device
circuit. On the bottom layer, additional footprints of optional
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Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
components are included to ease board modification for
different input/output configurations.
Soft-Start Input (SS)
The device utilizes an adjustable soft-start function to
limit inrush current during startup. The soft-start time is
programmed by the value of the external capacitor from
SS to GND (C1). The selected output capacitance (CSEL)
and the output voltage (VOUT) determine the minimum
value of C1, as shown by the following equation:
C1 ≥ 28 × 10 −3 × C SEL × VOUT
where C1 is in nF and CSEL is in µF
The soft-start time (tSS) is calculated by the equation
below:
t SS = C1/ 5.55
where tSS is in ms and C1 is in nF.
Programmable Undervoltage-Lockout (UVLO)
The EV kit offers an adjustable input undervoltagelockout level by resistor dividers connected between IN,
EN/UVLO, and GND pins. For normal operation, a shunt
should not be installed across pins 1-2 on JU1 to enable
the output through an internal pullup 3.3MΩ resistor from
EN/UVLO pin to IN pin. To disable the output, install the
shunt across pins 1-2 on JU1 to pull EN/UVLO pin to
GND. See Table 1 for JU1 jumper setting details. The
EV kit also provides an optional R3 PCB footprint to
program a UVLO threshold voltage at which an inputvoltage level device turns on. The R3 resistor can be
calculated by the following equation:
R3 =
4009.5
(VINU − 1.215)
where VINU is the input voltage at which the device is
required to turn on, and R3 unit is in kΩ.
Table 1. UVLO Enable/Disable
Configuration (JU1)
SHUNT
POSITION
EN PIN
MAXM17545_
OUTPUT
Installed
Connected to GND
Disable
Not installed*
Connected to VIN
Enable
*Default position.
Maxim Integrated │ 2
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
MAXM17545 3.3V Output
Evaluation Kit
Mode Selection (MODE)
The device’s MODE pin can be used to select among the
PWM, PFM, or DCM modes of operation in advance of
constant frequency or high efficiency at light load. The
logic state of the MODE pin is latched when the VCC
and EN/UVLO voltage exceed the respective UVLO rising
thresholds and all internal voltages are ready to allow LX
switching. The changes on the MODE pin are ignored
during normal operation. Refer to the MAXM17545 IC
data sheet for more information on the PWM, PFM, and
DCM modes of operation. Table 2 shows EV kit jumper
settings that can be used to configure the desired mode
of operation.
External Clock Synchronization (SYNC)
The internal oscillator of the device can be synchronized
to an external clock signal to eliminate beat frequency
between regulators through the SYNC pin. The external
synchronization clock frequency must be between 1.1fSW
to 1.4fSW, where fSW is the frequency of operation set
by R5. The minimum external clock high pulse width and
amplitude should be greater than 50ns and 2.1V, respectively.
The minimum external clock low pulse width should be
greater than 160ns, and the maximum external clock
low pulse amplitude should be less than 0.8V. Table 3
describes the connection of the SYNC pin.
Setting VOUT with a Resistive Voltage-Divider
at FB
The EV kit is preset for 3.3V and offers an adjustable-output voltage range of 0.9V to 12V at 1.7A
maximum load. The adjustable output voltage can be
programmed by the set of resistor-dividers R1 and R2.
Refer to Table 1 (Selection Component Values) of the
MAXM17545 IC data sheet to select optimal component values for each specific input voltage range from
4.5V to 42V and an output voltage from 0.9V to 12V.
To obtain a different output voltage other than default
setting outputs in Table 1, only seven component (R1, R2,
R4, C1, C2, C3, and C8) values are needed to modify
the equation described in the Setting the Output Voltage
section of the MAXM17545 IC data sheet.
Table 3. SYNC Description (JU3)
SHUNT
POSITION
SYNC PIN
MAXM17545_
SYNC
1-2*
Connected to
SGND
SYNC feature
unused
Not installed
Connected to test
loop on PCB
Frequency can be
synchronized with an
external clock
*Default position.
Table 2. MODE Description (JU2)
SHUNT
POSITION
MODE PIN
MAXM17545_
MODE
Not installed
Unconnected
PFM mode of
operation
1-2
Connected to
VCC
DCM mode of
operation
2-3*
Connected to
GND
PWM mode of
operation
*Default position.
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MAXM17545 3.3V Output
Evaluation Kit
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
Typical Operating Characteristics
(VIN = 4.5V - 42V, VOUT = 3.3V, IOUT = 0 – 1.7A, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
VOUT = 3.3V, PFM MODE toc01
100
90
90
80
80
70
VIN = 24V,
fSW = 400kHz
60
VIN = 12V,
fSW = 400kHz
50
40
EFFICIENCY (%)
EFFICIENCY (%)
100
VIN = 36V,
fSW = 400kHz
500
1000
VIN = 24V,
fSW = 400kHz
70
60
40
1500
MODE = SGND
0
500
EFFICIENCY vs. OUTPUT CURRENT
VOUT = 3.3V, DCM MODE toc03
80
3.400
VIN = 24V,
fSW = 400kHz
VIN = 12V,
fSW = 400kHz
50
40
VIN = 5.0V
fSW = 400kHz
VIN = 36V,
fSW = 400kHz
3.200
VIN = 24V
fSW = 400kHz
3.100
500
1000
3.000
1500
0
500
3.4000
VIN = 24V
fSW = 400kHz
3.1000
3.0000
3.5000
VIN = 12V
fSW =400kHz
3.3000
3.2000
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VIN = 5.0V
fSW = 400kHz
3.4000
500
1000
OUTPUT CURRENT (mA)
VIN = 12V
fSW = 400kHz
VIN = 24V
VIN = 36V
fSW = 400kHz f = 400kHz
SW
3.1000
1500
toc06
3.3000
3.2000
VIN = 36V
fSW = 400kHz
MODE = SGND
0
1500
LOAD REGULATION
VOUT = 3.3V, DCM MODE
3.6000
toc05
VOUT (V)
VOUT (V)
VIN = 5.0V
fSW = 400kHz
1000
OUTPUT CURRENT (mA)
LOAD REGULATION
VOUT = 3.3V, PWM MODE
3.5000
VIN = 36V
fSW = 400kHz
MODE = OPEN
OUTPUT CURRENT (mA)
3.6000
VIN = 12V
fSW = 400kHz
3.300
MODE = VCC
0
toc04
VOUT (V)
EFFICIENCY (%)
3.500
60
1500
LOAD REGULATION
VOUT = 3.3V, PFM MODE
3.600
90
70
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
100
VIN = 36V,
fSW = 400kHz
VIN = 12V,
fSW = 400kHz
50
MODE = OPEN
0
EFFICIENCY vs. OUTPUT CURRENT
VOUT = 3.3V, PWM MODE toc02
3.0000
MODE = VCC
0
500
1000
1500
OUTPUT CURRENT (mA)
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Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
MAXM17545 3.3V Output
Evaluation Kit
Typical Operating Characteristics (continued)
(VIN = 4.5V - 42V, VOUT = 3.3V, IOUT = 0 – 1.7A, TA = +25°C, unless otherwise noted.)
LOAD CURRENT TRANSIENT RESPONSE
VIN = 24V, VOUT = 3.3V, IOUT = 0.05A–0.85A,
MODE = SGND
toc08
LOAD CURRENT TRANSIENT RESPONSE
VIN = 24V, VOUT = 3.3V, IOUT = 0.05A - 0.85A,
MODE = OPEN
toc07
1A/div
IOUT
100mV/div
(AC
COUPLED)
VOUT
1A/div
IOUT
100mV/div
(AC
COUPLED)
VOUT
200µs/div
200µs/div
LOAD CURRENT TRANSIENT RESPONSE
VIN = 24V, VOUT = 3.3V, IOUT = 0.85A–1.7A,
MODE = SGND
toc10
LOAD CURRENT TRANSIENT RESPONSE
VIN = 24V, VOUT = 3.3V, IOUT = 0.05A–0.85A,
MODE = VCC
toc09
1A/div
IOUT
100mV/div
(AC
COUPLED)
VOUT
1A/div
IOUT
100mV/div
(AC
COUPLED)
VOUT
200µs/div
200µs/div
40
PHASE
GAIN (dB)
30
toc11
150
120
90
60
20
30
10
0
0
GAIN
-10
-30
-20
-60
-30
-90
-40
-120
-50
1k
10k
100k
PHASE MARGIN (°)
50
CLOSED-LOOP BODE PLOT
VIN = 24V, VOUT = 3.3V, IOUT = 1.7A,
MODE = SGND
-150
1Meg
FREQUENCY (Hz)
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MAXM17545 3.3V Output
Evaluation Kit
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
Component Suppliers
SUPPLIER
WEBSITE
Murata Americas
www.murata.com
NEC TOKIN America, Inc.
www.nec-tokinamerica.com
Panasonic Corp.
www.panasonic.com
SANYO Electric Co., Ltd.
www.sanyodevice.com
TDK Corp.
www.component.tdk.com
TOKO America, Inc.
www.tokoam.com
Note: Indicate that you are using the MAXM17545 when contacting these component suppliers.
Component List and Schematic
Refer to the following files attached to this data sheet for
component information and schematic:
●● MAXM17545_EV_BOM.xls
●● MAXM17545_EV_Schematic.pdf
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MAXM17545 3.3V Output
Evaluation Kit
Figure 1. MAXM17545 EV Kit Component Placement Guide—
Component-Side
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
Figure 2. MAXM17545 EV Kit Component Placement Guide—
Solder-Side
Figure 3. MAXM17545 EV Kit PCB Layout—Component-Side
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MAXM17545 3.3V Output
Evaluation Kit
Figure 4. MAXM17545 EV Kit PCB Layout—PGND Layer 2
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
Figure 5. MAXM17545 EV Kit PCB Layout—PGND Layer 3
Figure 6. MAXM17545 EV Kit PCB Layout—Solder-Side
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MAXM17545 3.3V Output
Evaluation Kit
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
Ordering Information
PART
TYPE
MAXM17545EVKIT#
EV Kit
#Denotes RoHS compliant.
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Maxim Integrated │ 9
Evaluates: MAXM17545 in 3.3V
Output-Voltage Application
MAXM17545 3.3V Output
Evaluation Kit
Revision History
REVISION
NUMBER
REVISION
DATE
0
5/15
DESCRIPTION
Initial release
PAGES
CHANGED
—
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2015 Maxim Integrated Products, Inc. │ 10
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