MAX17761 3.3V Output
Evaluation Kit
Evaluates: MAX17761
3.3V Output-Voltage Application
General Description
The MAX17761 3.3V output EV kit is a proven design
to evaluate the MAX17761 high-efficiency, high-voltage,
synchronous step-down DC-DC converter in a TDFN
package. The EV kit generates 3.3V at load currents up
to 1A from a 4.5V to 76V input supply. The EV kit features
a 400kHz switching frequency for optimum efficiency and
component size. The EV kit features adjustable input
undervoltage lockout, adjustable soft-start, adjustable
switching frequency, adjustable current limit, open-drain
RESET
signal and external frequency synchronization.
Quick Start
Recommended Equipment
●
MAX17761 3.3V output EV kit
● 4.5V to 76V, 2A DC input power supply
● Load capable of sinking 1A
● Digital voltmeter (DVM)
Procedure
Features
The EV kit is fully assembled and tested. Follow the steps
below to verify board operation.
Caution: Do not turn
on power supply until all connections are completed.
1)
2)
Set the power supply at a voltage between 4.5V and
76V. Disable the power supply.
Connect the positive terminal of the power supply to
the VIN 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 1-2 on
jumper JU1, JU2, and JU3 (see
Table 3
for details).
Turn on the DC power supply.
Enable the load.
Verify that the DVM displays 3.3
● Operates from a 4.5V to 76V Input Supply
●
3.3V Output Voltage
● Up to 1A Output Current
● 400kHz Switching Frequency
● Enable/UVLO Input, Resistor-Programmable UVLO
Threshold
● Adjustable Soft-Start Time
● MODE/ILIM Pin to Select Among PWM or PFM
Modes and 1.6A or 1.14A current limits
● Auxiliary Bootstrap LDO to improve efficiency
● Open-Drain RESET
Output
● External Frequency Synchronization
● Overcurrent and Overtemperature Protection
● Proven PCB Layout
● Fully Assembled and Tested
3)
4)
5)
6)
7)
Ordering Information
appears at end of data sheet.
319-100077; Rev 1; 2/18
MAX17761 3.3V Output
Evaluation Kit
Detailed Description
Evaluates: MAX17761
3.3V Output-Voltage Application
Current Limit and Mode of Operation Selection
The following table lists the values of the resistor R5 to
program PWM or PFM modes of operation and 1.6A or
1.14A peak current limits.
The MAX17761 3.3V Output EV kit provides a proven
design to evaluate the MAX17761 high-efficiency, high-
voltage, synchronous step-down DC-DC converter. The
EV kit generates 3.3V at load currents up to 1A from a
4.5V to 76V input supply. The EV kit features a 400kHz
switching frequency for optimum efficiency and compo-
nent size.
The EV kit includes an EN/UVLO PCB pad and JU1 to
enable the output at a desired input voltage. The RT/SYNC
PCB pad and JU3 allow an external clock to synchronize
the device. An additional
RESET
PCB pad is available for
monitoring when the converter output is in regulation.
Table 1. R
ILIM
Resistor vs. Modes of
Operation and Peak Current Limit
R5
(kΩ)
OPEN
422
243
121
MODE OF
OPERATION
PFM
PFM
PWM
PWM
PEAK CURRENT
LIMIT (A)
1.6
1.14
1.6
1.14
Soft-Start Input (SS)
The device implements adjustable soft-start operation to
reduce inrush current. A capacitor connected from the SS
pin to SGND programs the soft-start time for the corre-
sponding output voltage. The selected output capacitance
(C
SEL
) and the output voltage (V
OUT
) determine the mini-
mum required soft-start capacitor as follows:
C
SS
≥ 30 x 10
-6
x C
SEL
x V
OUT
The soft-start time (t
SS
) is related to the capacitor con-
nected at SS (C
SS
) by the following equation:
t
SS
=
6.25
×
10
−
6
C
SS
The mode of operation cannot be changed on-the-fly after
power-up.
Switching Frequency Selection and
External Frequency synchronization
The RT/SYNC pin programs the switching frequency of
the converter. The resistor R7 sets the switching frequency
of the part at any one of four discrete frequencies—
200kHz, 300kHz, 400kHz, and 600kHz. The following
table gives the resistor values.
Table 2. Switching Frequency
vs. RT Resistor
SWITCHING FREQUENCY (kHz)
200
300
400
600
R7 (kΩ)
210
140
105
69.8
For example, to program a 5.3ms soft-start time, a 33nF
capacitor should be connected from the SS pin to SGND.
The minimum possible soft-start time is 5ms.
Regulator Enable/Undervoltage-Lockout Level
(EN/UVLO)
The device offers an adjustable input undervoltage-lock-
out level. For always on operation, no shunt should be
installed across JU1. To disable the output, install a shunt
across pins 2-3 on JU1 and the EN/UVLO pin is pulled to
GND. See
Table 3
for JU1 settings.
Set the voltage at which each converter turns on with a
resistive voltage-divider connected from VIN to SGND.
Connect the center node of the divider to EN/UVLO pin.
Choose R1 as follows:
R1 ≤ (110000 x V
INU
)
Where V
INU
is the input voltage at which the MAX17761
is required to turn ON and R1 is in Ω. Calculate the value
of R2 as follows:
R2
=
1.215
×
R1
(V
INU
−
1.215
+
(2.5µA
×
R1))
The internal oscillator of the MAX17761 can be synchro-
nized to an external clock signal on the RT/SYNC pin. A
shunt should be placed across the jumper JU3 for this
purpose. The external synchronization clock frequency
must be between 1.15 x f
SW
and 1.4 x f
SW
, where f
SW
is
the frequency programmed by R7.
Table 3. Regulator Enable (EN/UVLO)
Description (JU1)
SHUNT
POSITION
Not Installed
1-2
2-3
EN/UVLO PIN
Floating
Connected to the center
node of resistor-divider
R1 and R2
Connected to SGND
MAX17761 OUTPUT
Always ON
Enabled, UVLO level set
through the R1 and R2
resistors
Disabled
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Maxim Integrated
│ 2
MAX17761 3.3V Output
Evaluation Kit
MAX17761 EV Kit Performance Report
LOAD AND LINE REGULATION
(3.3V OUTPUT, PWM MODE)
3.36
3.35
Evaluates: MAX17761
3.3V Output-Voltage Application
toc01
EFFICIENCY vs. LOAD CURRENT
(3.3V OUTPUT, PWM MODE)
100
V
IN
= 12V V
IN
= 24V
V
IN
= 36V
toc02
OUTPUT VOLTAGE (V)
3.34
3.33
3.32
3.31
3.30
3.29
V
IN
= 12V
V
IN
= 24V
V
IN
= 48V
V
IN
=48V
V
IN
= 76V
90
EFFICIENCY (%)
80
70
V
IN
= 48V
V
IN
= 60V
V
IN
= 76V
V
IN
= 36V
V
IN
= 60V
60
0.00
0.20
0.40
0.60
0.80
LOAD CURRENT (A)
CONDITIONS: f
SW
= 400kHz
1.00
50
0.00
0.20
0.40
0.60
0.80
LOAD CURRENT (A)
CONDITIONS: f
SW
= 400kHz
1.00
LOAD AND LINE REGULATION
(3.3V OUTPUT, PFM MODE)
3.50
toc03
EFFICIENCY VS. LOAD CURRENT
(3.3V OUTPUT, PFM MODE)
100
90
toc04
3.45
V
IN
= 48V
OUTPUT VOLTAGE (V)
3.40
V
IN
= 76V
EFFICIENCY (%)
V
IN
= 60V
80
70
V
IN
= 48V
60
50
V
IN
= 76V
V
IN
= 60V
V
IN
= 12V
V
IN
= 36V
V
IN
= 24V
3.35
V
IN
= 12V
3.30
V
IN
= 24V
V
IN
= 36V
40
30
3.25
0.00
0.20
0.40
0.60
LOAD CURRENT (A)
CONDITIONS: f
SW
= 400kHz
0.80
1.00
0.00
0.01
0.10
LOAD CURRENT (A)
CONDITIONS: f
SW
= 400kHz
1.00
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Maxim Integrated
│
3
MAX17761 3.3V Output
Evaluation Kit
MAX17761 EV Kit Performance Report (continued)
LOAD CURRENT STEPPED FROM 0A TO 0.25A
(3.3V OUTPUT, PWM MODE)
toc05
Evaluates: MAX17761
3.3V Output-Voltage Application
LOAD CURRENT STEPPED FROM 0.5A TO 0.75A
(3.3V OUTPUT, PWM MODE)
toc06
V
OUT
(AC)
50mV/div
V
OUT
(AC)
50mV/div
I
OUT
100µs/div
100mA/div
I
OUT
100µs/div
200mA/div
LOAD CURRENT STEPPED FROM 0A TO 0.25A
(3.3V OUTPUT, PFM MODE)
toc07
BODE PLOT
(3.3V OUTPUT, 1A LOAD CURRENT)
40
30
toc08
V
OUT
(AC)
100
100mV/div
20
10
0
-10
CROSSOVER
FREQUENCY = 15.8kHz,
PHASE MARGIN = 69.8 °
10
3
10
4
FREQUENCY (Hz)
10
5
50
0
I
OUT
1ms/div
100mA/div
-20
-50
CONDITIONS: f
SW
= 400kHz, 24V INPUT
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Maxim Integrated
│
4
PHASE (°)
GAIN (dB)
MAX17761 3.3V Output
Evaluation Kit
MAX17761 EV Kit Bill of Materials
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
Description
0.1uF 10%, 100V ,X7R,Ceramic capacitor (0603)
2.2uF 10%, 100V ,X7R,Ceramic capacitor (1210)
22uF 20%,100V, Electrolytic capacitor
1uF 10%, 6.3V ,X7R,Ceramic capacitor (0603)
47pF, 5%, 25V, COG, Ceramic capacitor(0402)
33nF, 10%, 25V, X7R, Ceramic capacitor(0402)
47uF,10%,10V, X7R,Ceramic capacitor (1210)
6800pF,10%,50V,X7R,Ceramic capacitor(0402)
3-pin header (36-pin header 0.1” centers )
2-pin header (36-pin header 0.1” centers )
INDUCTOR, 22 uH,3.6A
430k ohm ±1%,1/10W, resistor (0603)
137k ohm ±1%,1/10W, resistor (0603)
57.6k ohm ±1%,1/10W, resistor (0402)
18.2k ohm ±1%, 1/16W,resistor (0402)
Not installed, OPEN (0402)
10k ohm ±1%,1/10W, resistor (0402)
105k ohm ±1%,1/16W, resistor (0402)
15.4k ohm ±1%, 1/10W, resistor (0402)
Buck Converter
MAX17761ATC+
Shunts (JU1, JU2, JU3)
Quantity
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1
0
1
1
1
1
3
Designator
C1
C2
C3
C4
C5
C6
C7
C8
JU1
JU2,JU3
L1
R1
R2
R3
R4
R5
R6
R7
R8
U1
-
Evaluates: MAX17761
3.3V Output-Voltage Application
Part Number
MURATA GRM188R72A104KA35, TDK
CC0603KRX7R0BB104
MURATA GRM32ER72A225KA35, TDK
CGA6N3X7R2A225K230
PANASONIC EEE-TG2A220UP
MURATA GRM188R70J105KA01, SAMSUNG
ELECTRONICS CL10B105KQ8NNNC
MURATA GRM1555C1E470JA01
MURATA GRM155R71E333KA88
MURATA GRM32ER71A476KE15
MURATA GRM155R71H682KA88
Sullins: PEC03SAAN
Sullins: PEC02SAAN
Coilcraft XAL5050-223ME
Any
Any
Any
Any
Any
Any
Any
Any
MAX17761ATC+
Sullins: STC02SYAN
Component Suppliers
SUPPLIER
Murata Americas
Panasonic Corp.
Coilcraft
TDK Corp.
Samsung Electronics
SullinsCorp
WEBSITE
www.murata.com
www.panasonic.com
www.coilcraft.com
www.tdk.com
www.samsung.com
www.sullinscorp.com
Ordering Information
PART
MAX17761EVKITA#
#Denotes RoHS compliant.
TYPE
EV Kit
Note:
Indicate that you are using the MAX17761 when contacting
these component suppliers.
www.maximintegrated.com
Maxim Integrated
│
5
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