MAXM17761 5V Output
Evaluation Kit
Evaluates: MAXM17761
5V Output-Voltage Application
General Description
The MAXM17761 5V-output evaluation kit (EV kit) pro-
vides a proven design to evaluate the MAXM17761 high-
voltage, high-efficiency, synchronous step-down DC-DC
converter. The EV kit is preset for 5V output at load cur-
rents up to 1A and features a 537kHz switching frequency
for optimum efficiency and component size. The EV kit
features an adjustable input undervoltage lockout, adjust-
able soft-start, open-drain
RESET
signal, and external
frequency synchronization. The MAXM17761 module
data sheet provides a complete description of the part
that should be read in conjunction with this data sheet
prior to operating the EV kit. For full features, benefits
and parameters of the MAXM17761 module, refer to the
MAXM17761 data sheet.
Quick Start
●
●
●
●
Recommended Equipment
One 10V–76V DC, 1A power supply
5W resistive load with 1A sink capacity
Four digital multimeters (DMM)
One MAXM17761EVKIT# EV kit
Equipment Setup and Test Procedure
The EV kit is fully assembled and tested. Follow the steps
below to verify the board operation.
Caution: Do not turn on power supply until all con-
nections are completed.
1)
2)
Set the power supply at a voltage between 10V and
76V. Disable the power supply.
Connect the positive terminal of the power supply to
the VIN_EMI PCB pad and the negative terminal to
the nearest PGND PCB pad. Connect the positive
terminal of the 1A load to the VOUT PCB pad and
the negative terminal to the nearest PGND PCB pad.
Connect the DVM across the VOUT PCB pad and
the nearest PGND PCB pad.
Verify that shunts are installed across pins 2-3 on
jumper J1 (see
Table 1
for details) and across pin
1-2 of J2.
Turn on the DC power supply.
Enable the load.
Verify that the DVM displays 5V across the output
terminals.
Benefits and Features
●
Highly Integrated Solution with Integrated Shielded
Inductor
●
Wide 10V to 76V Input Range
●
Up to 1A Output Current
●
High 91% Efficiency (V
IN
= 12V, V
OUT
= 5V at 0.2A)
●
537kHz Switching Frequency
●
Enable/UVLO Input, Resistor-Programmable UVLO
Threshold
●
Adjustable Soft-Start Time
●
Open-Drain
RESET
Output
●
Provision for External Frequency Synchronization
●
Overcurrent and Overtemperature Protection
●
Low-Profile, Surface-Mount Components
●
Proven PCB Layout
●
Fully Assembled and Tested
●
CISPR-22 Class B Compliant
3)
4)
5)
6)
7)
Ordering Information
appears at end of data sheet.
319-100079; Rev 0; 9/17
MAXM17761 5V Output
Evaluation Kit
Detailed Description
Evaluates: MAXM17761
5V Output-Voltage Application
jumper J2, the resistive divider is formed by R7 and R9.
See
Table 2
for J2 settings.
To get different output voltages, refer to Table 2 in
MAXM17761 datasheet. R7 and R9 of the EV kit corre-
spond to R
U
and R
B
of
Setting the Output Voltage
section
in the MAXM17761 data sheet.
The MAXM17761 5V output EV kit is designed to dem-
onstrate the salient features of the MAXM17761 power
module. The MAXM17761 EV kit includes an EN/UVLO
PCB pad and jumper J1 to enable the output at a desired
input voltage. The RT/SYNC PCB pad allows an external
clock interface to synchronize with the device. An addi-
tional
RESET
PCB pad is available for monitoring if the
converter output is in regulation.
On the bottom layer of the EV kit, additional footprints for
optional components are included to ease board modifi-
cation for different input/output configurations. The evalu-
ation board has place holders available on the bottom
layer for installation of EMI filter components.
Soft-Start Capacitor
MAXM17761 offers an adjustable soft-start function to limit
inrush current during startup. The soft-start time is adjusted
by changing the value of C
10
, the external capacitor from
SS pin to PGND. The capacitance required for a given soft-
start time (t
SS
) is given by the following equation:
Setting the Switching Frequency
Selection of switching frequency must consider input
Voltage range, desired output voltage, t
ON-MIN
of the
MAXM17761, and ambient temperature. To optimize
efficiency and component size, a switching frequency of
537kHz is chosen. Resistor R3 connected between RT/
SYNC and PGND pins, programs the desired switching
frequency. Using Table 1 in the MAXM17761 data sheet,
R3 is chosen to be 69.8kΩ.
Table 2 in the MAXM17761
data sheet lists the various switching frequency recom-
mendations for optimized designs.
C
SS
≥ 6.25 × 10
-6
× t
SS
For example, to program a 5ms soft-start time, a 33nF
capacitor should be connected from SS pin to PGND.
A parallel combination of the internal SS_C capacitor and
the optional external capacitor (C10) can also be used to
program soft-start time.
Enable/Undervoltage-Lockout (EN/UVLO)
Input Capacitor Selection
The input capacitor serves to reduce the current peaks
drawn from the input power supply and also reduce
switching frequency voltage ripple at the input. Table 2in
the MAXM17761 data sheet summarizes the choice of
Input capacitor for various requirements. Using this table,
the input capacitor (C2) for this EV kit is chosen to be
2.2µF/100V.
MAXM17761 offers an adjustable input undervoltage lock-
out feature. In this EV kit, place a shunt across pins 2-3
of Jumper J1 to enable the power conversion when V
IN
exceeds 9.5V. To disable the output, install a shunt across
pins 1-2 of J1. Leave jumper J1 pins open for always-on
operation. See
Table 1
for J1 settings. Calculate the value
of R1 and R2 based on the following equations.
R1 ≤ (110000 x V
INU
)
Where V
INU
is the input voltage at which the MAXM17761
is required to turn on and R1 is in Ω.
Calculate the value of R2 in Ω as follows
R2
=
1.215
×
R1
(
V
INU
−
1.215
+
(
2.5
µ
A
×
R1
)
)
Output Capacitor Selection
Ceramic output capacitors are preferred due to their sta-
bility over temperature in industrial applications. Table 2 in
MAXM17761 data sheet summarizes the choice of output
capacitor for various requirements. Using this table, the
output capacitor (C12) for this EV kit is chosen to be
47μF/10V.
For the MAXM17761 to turn on at 9.5V input, resistor
(R1) is chosen as 806kΩ and resistor (R2) is calculated
as 95.3kΩ.
External Clock Synchronization (RT/SYNC)
Adjusting Output Voltage
MAXM17761 supports an adjustable output voltage
range, from 0.8V to 5V, using a feedback resistive divider
from VOUT to PGND. In this EV kit, by placing a shunt
across 1-2 of jumper J2, the resistive divider is formed by
R7 and internal 22.1kΩ. By placing a shunt across 2-3 of
The internal oscillator of MAXM17761 can be synchro-
nized to an external clock signal through the RT/SYNC
pin. External synchronization clock frequency must be
between 1.15
×
f
SW
and 1.4
×
f
SW
, where f
SW
is the fre-
quency of operation as set by resistor R3. The minimum
external clock low pulse width should be greater than
40ns, and the amplitude of external clock pulse should be
greater 1.22V.
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MAXM17761 5V Output
Evaluation Kit
EXTVCC Linear Regulator
Evaluates: MAXM17761
5V Output-Voltage Application
Table 1. UVLO Enable/Disable
Configuration (J1)
POSITION
Not Installed
EN/UVLO PIN
Floating
Connected to the
center node of
resistor-divider
R1 and R2
Connected to
PGND
MAXM17761 OUTPUT
Enabled
Programmed to startup
at desired input voltage
level set by R1 and R2
Disabled
Powering VCC from EXTVCC increases the efficiency at
higher input voltages. If the applied EXTVCC voltage is
greater than 4.74V (typ), VCC is powered from EXTVCC.
If EXTVCC is lower than 4.74V (typ), VCC is powered
from VIN. Refer to the MAXM17761 module data sheet
for further information. Resistor R6 (0Ω) connects VOUT
to EXTVCC in this EV kit.
2–3*
Electromagnetic Interference (EMI)
Compliance to conducted emissions (CE) standards
requires an EMI filter at the input of a switching power
converter. The EMI filter attenuates high-frequency cur-
rents drawn by the switching power converter and limits
the noise injected back into the input power source.
The MAXM17761 EV kit PCB has designated footprints
on the bottom side for placement of EMI filter compo-
nents. Use of EMI filter components, as shown in the
schematic, results in lower conducted emissions, below
CISPR22 Class B limits. Cut open the trace at L
1
, before
installing EMI filter components. The MAXM17761 EV kit
PCB layout is also designed to limit radiated emissions
from switching nodes of the power converter, resulting in
radiated emissions below CISPR22 Class B limits.
1–2
*Default
position.
Table 2. Adjusting the Output Voltage (J2)
POSITION
1–2*
2–3
Not Installed
*Default
position.
FB PIN
Connected to the center node of resistor-
divider R7 and internal feedback resistor.
Connected to the center node of resistor-
divider R7 and R9
Results in V
OUT
= 0.8V
Hot-Plug-In and Long Input Cables
The MAXM17761 EV kit PCB provides an optional elec-
trolytic capacitor (C
1
, 22µF/100V). This capacitor limits
the peak voltage at the input of the MAXM17761 power
module, when the DC input source is “Hot-Plugged” to the
EV kit input terminals with long input cables. The equiva-
lent series resistance (ESR) of the electrolytic capacitor
dampens the oscillations caused by interaction of the
inductance of the long input cables, and the ceramic
capacitors at the power module Input.
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MAXM17761 5V Output
Evaluation Kit
EV Kit Performance Report
Evaluates: MAXM17761
5V Output-Voltage Application
(V
IN
= 24V, V
OUT
= 5V, I
OUT
= 1A, T
A
= 25°C. All voltages are referenced to PGND, unless otherwise noted.)
STARTUP THROUGH ENABLE
(LOAD RESISTANCE = 5Ω)
EFFICIENCY vs. LOAD CURRENT
toc01
100
90
toc02
V
EN/UVLO
5V/div
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0
200
V
IN
= 12V
V
IN
= 24V
V
IN
= 48V
V
IN
= 60V
V
IN
= 76V
MODE: PWM
400
600
800
1,000
LX
10V/div
V
OUT
RESET
1ms/div
5V/div
5V/div
LOAD CURRENT (mA)
LOAD REGULATION
5.20
toc03
LINE REGULATION
5.100
5.095
toc04
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
5.15
V
IN
= 76V
5.10
V
IN
= 60V
V
IN
= 24V
5.090
5.085
5.080
5.075
5.070
I
OUT
= 1A
I
OUT
= 0.5A
I
OUT
= 0.A
0
10
20
30
40
50
60
70
80
5.05
V
IN
= 48V
V
IN
= 12V
MODE: PWM
600
800
1000
5.065
5.060
5.00
0
200
400
LOAD CURRENT (mA)
INPUT VOLTAGE(V)
LOAD TRANSIENT RESPONSE
(CURRENT STEP 0A to 0.25A)
toc05
V
OUT
(AC)
50mV/div
MODE: PWM
V
OUT
= 5V
I
OUT
100µs/div
200mA/div
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MAXM17761 5V Output
Evaluation Kit
EV Kit Performance Report (continued)
Evaluates: MAXM17761
5V Output-Voltage Application
(V
IN
= 24V, V
OUT
= 5V, I
OUT
= 1A, T
A
= 25°C. All voltages are referenced to PGND, unless otherwise noted.)
LOAD TRANSIENT RESPONSE
(CURRENT STEP 0.5A to 0.75A)
BODE PLOT
V
IN
= 24V, V
OUT
= 5V, I
OUT
= 1A
40
toc06
toc07
100
V
OUT
(AC)
50mV/div
GAIN(dB)
20
50
0
0
-20
-50
I
OUT
100µs/div
MODE: PWM
V
OUT
= 5V
200mA/div
f
C
= 22.3kHz
PM = 74.28
°
1k
10k
FREQUENCY(HZ)
100k
CONDUCTED EMISSION PLOT
(WITH FILTER, L1 = 6.8µH, C7 = 1µF, C8 = C9 = 4.7µF)
toc08
RADIATED EMISSION PLOT
(C1 = 22µF, C5 = 0.1µF, C2 = 2.2µF)
toc09
70
60
CISPR-22 CLASS B QP Limit
MAGNITUDE (dBµV/m)
70
60
50
40
30
20
10
0
MAGNITUDE (dBµV)
50
40
30
20
10
CISPR-22 CLASS B AVG Limit
CISPR-22 CLASS B QP Limit
PEAK
EMISSION
AVERAGE
EMISSION
1M
FREQUENCY (Hz)
CONDITIONS: V
IN
= 24V, V
OUT
= 5V, LOAD = 1A
10M
150K
30M
100M
FREQUENCY (Hz)
1G
CONDITIONS: V
IN
= 24V, V
OUT
= 5V, LOAD = 1A
Component Suppliers
SUPPLIER
Murata Americas
NEC TOKIN America, Inc.
Panasonic Corp.
SANYO Electric Co., Ltd.
TDK Corp.
TOKO America, Inc.
WEBSITE
www.murata.com
www.nec-tokinamerica.com
www.panasonic.com
www.sanyodevice.com
www.component.tdk.com
www.tokoam.com
Ordering Information
PART
MAXM17761EVKIT#
#Denotes RoHS compliant.
TYPE
EV Kit
Note:
Indicate that you are using the MAXM17761 when
contacting these component suppliers.
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