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MAX17633AEVKIT# Evaluation Kit
Evaluates: MAX17633
3.3V Output-Voltage Application
General Description
The MAX17633AEVKIT# 3.3V output evaluation kit (EV
kit) provides a proven design to evaluate the MAX17633A
high-voltage, high-efficiency, synchronous step-down
DC-DC converter. The EV kit is preset for 3.3V output at
load currents of 3.5A and features a 500kHz switching
frequency for optimum efficiency and component size.
The EV kit features an adjustable input undervoltage lock-
out, adjustable soft-start, open-drain
RESET
signal, and
external frequency synchronization. EV kit specifications,
settings, features and benefits are highlighted. For full
MAX17633A IC features, benefits and parameters, refer
to MAX17633 datasheet.
Quick Start
Recommended Equipment
● One MAX17633AEVKIT# EV kit
● One 0V to 36V DC, 5A power supply
● Load capable of sinking 3.5A current
● Digital voltmeter (DVM)
Equipment Setup and Test Procedure
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 complete.
1)
2)
Set the input power supply at a voltage between 4.5V
and 36V. Disable the power supply.
Connect the positive terminal of the input power
supply to the VIN PCB pad and the negative terminal
to the nearest PGND pad. Connect the positive
terminal of the 3.5A load to the VOUT pad and the
negative terminal to the nearest PGND pad.
Connect a DVM across the VOUT pad and the nearest
PGND pad.
Verify that shunts are not installed on jumper JU1
(see
Table 1
for details).
Select the shunt position on jumper JU2 according
to the intended mode of operation (see
Table 2
for
details).
Turn on the input power supply.
Enable the load.
Verify that the DVM displays 3.3V.
Features
●
●
●
●
●
●
●
●
●
●
●
Wide 4.5V to 36V Input Range
Programmed 3.3V Output, 3.5A Load Current
500kHz Switching Frequency
EN/UVLO Input, Resistor-Programmable UVLO
Threshold
Programmed 1ms Soft-Start Time
Selectable PWM, PFM, and DCM Modes
Open-Drain
RESET
Output Pulled Up To 5V of
INTVCC
Provision for External Frequency Synchronization
Overcurrent and Overtemperature Protection
Proven PCB Layout
Fully Assembled and Tested
3)
4)
5)
6)
7)
8)
Ordering Information
appears at end of data sheet.
319-100197; Rev 1; 8/18
MAX17633AEVKIT# Evaluation Kit
Evaluates: MAX17633
3.3V Output-Voltage Application
Enable/Undervoltage-Lockout (EN/UVLO)
Programming
Detailed Description of Hardware
The MAX17633AEVKIT# is designed to demonstrate the
salient features of the MAX17633A. The EV kit includes
an EN/UVLO pad and jumper JU1 to enable the output at
a desired input voltage. The MODE/SYNC pad allows an
external clock interface to synchronize the device. Jumper
JU2 allows selection of a particular mode of operation
based on light-load performance requirements. An addi-
tional
RESET
pad is available for monitoring the status of
the output voltage.
Setting the Switching Frequency
Switching frequency selection must consider input-voltage
range, desired output voltage, t
ON(MIN)
, and t
OFF(MIN)
of
the MAX17633A and ambient temperature. To optimize
converter size and efficiency of the EV kit, a switching fre-
quency of 500kHz is chosen for 3.3V-programmed output.
Resistor R5 connected between RT and SGND pins, pro-
grams the desired switching frequency. R5 resistor is kept
open for a default 500kHz switching frequency. To program
the switching frequency, the R5 resistor is calculated as
follows:
21000
=
R5
−
1.7
f
SW
where R5 is in kΩ and f
SW
is in kHz.
The device offers an adjustable input undervoltage-lockout
level, where output is enabled at the minimum desired
input-voltage level. For always-enable operation, a shunt
should be installed across pins 1-2 on jumper JU1, which
pulls up the EN/UVLO to VIN. In order to disable the
output, install a shunt across pins 2-3 on JU1, which pulls
down the EN/UVLO pin to VSGND. See
Table 1
for JU1
settings. Set the input voltage level (input undervoltage-
lockout level) above which the device turns on with the
resistive voltage-divider R1 and R2 connected between
VIN and SGND.
Choose R1 to be 3.32MΩ and then calculate R2 as
follows:
R2
≥
4033.8
(V
INU
−
1.215)
where V
INU
is the input voltage at that the device requires
to turn on.
Table 1. Regulator Enable (EN/UVLO)
Description (JU1)
SHUNT
POSITION
1-2
Not
Installed*
2-3
*Default position
EN/UVLO PIN
Connected to VIN
Connected to the
center node of
resistor-divider R1
and R2
Connected to SGND
MAX17633A EV KIT
OUTPUT
Enabled
Enabled, UVLO level
set through the
R1 and R2 resistors
Disabled
Soft-Start Programming
The EV kit offers an adjustable soft-start function to
limit inrush current during startup. The soft-start time
is adjusted by changing the value of C3, the external
capacitor from the SS pin to SGND. The selected output
capacitance (C
SEL
) and the output voltage (V
OUT
)
determine the minimum value of C3, as shown by the
following equation:
C3 ≥ 28 x 10
-6
x C
SEL
x V
OUT
The soft-start time (t
SS
) is related to the soft-start capaci-
tor C3 by the following equation:
t
SS
=
5.55
×
10
−
6
C3
For example, in order to program a 1ms soft-start time, C3
should be 5600pF.
www.maximintegrated.com
Maxim Integrated │
2
MAX17633AEVKIT# Evaluation Kit
Evaluates: MAX17633
3.3V Output-Voltage Application
External Clock Synchronization
(MODE/SYNC)
MODE Selection (MODE/SYNC)
The device’s MODE/SYNC pin can be used to select
among forced PWM, DCM, or PFM modes of operation
at light loads. The logic state of the MODE/SYNC pin is
latched when the VCC and EN/UVLO voltages exceed
the respective UVLO rising thresholds and all internal volt-
ages are ready to allow LX switching. State changes on
the MODE/SYNC pin are ignored during normal operation.
Refer to the MAX17633 IC datasheet for more information
on the PWM, DCM, and PFM modes of operation.
Table 2
shows the EV kit jumper (JU2) settings that can be used to
configure the desired mode of operation.
Table 2. MODE/SYNC Description (JU2)
SHUNT
POSITION
1-2
2-3*
Not
Installed
*Default position
MODE/SYNC PIN
Connected to INTVCC
Connected to SGND
Unconnected
MAX17633A EV KIT
OUTPUT
DCM mode of
operation
PWM mode of
operation
PFM model of
operation
The internal oscillator of the MAX17633A can be
synchronized to an external clock signal through the
MODE/ SYNC pin in DCM and PWM modes of operation.
The synchronization to an external clock is not supported
in PFM mode of operation. The external synchronization
clock frequency must be between 1.1 x f
SW
and 1.4 x
f
SW
, where f
SW
is the frequency of operation as set by
R5 resistor. The minimum external clock high pulse width
should be greater than 50ns and minimum external low
pulse width should be greater than 160ns. The source
impedance of the external SYNC signal source should be
below 25kΩ for reliable operation.
Hot Plug-In and Long Input Cables
The MAX17633AEVKIT# PCB layout provides an optional
electrolytic capacitor (C6, 10μF/50V). This capacitor limits
the peak voltage at the input of the MAX17633A when
the DC input source is “Hot-Plugged” to the EV kit input
terminals with long input cables. The equivalent 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.
www.maximintegrated.com
Maxim Integrated │
3
MAX17633AEVKIT# Evaluation Kit
Evaluates: MAX17633
3.3V Output-Voltage Application
MAX17633A EV Kit Performance Report
(V
IN
= 24V, L = 5.6μH (XAL5050-562ME), f
SW
= 500kHz, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
100
90
80
toc01
EFFICIENCY vs. LOAD CURRENT
100
95
90
toc02
EFFICIENCY vs. LOAD CURRENT
100
90
80
toc03
EFFICIENCY (%)
60
50
40
30
20
10
0
0
500
V
IN
= 12V V
IN
= 24V
V
IN
= 4.5V
EFFICIENCY (%)
EFFICIENCY (%)
70
V
IN
= 36V
85
80
75
70
65
60
55
50
10
100
1000
LOAD CURRENT (mA)
CONDITIONS: PFM MODE
V
IN
= 4.5V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
70
60
50
40
30
20
10
0
50
500
LOAD CURRENT (mA)
CONDITIONS: DCM MODE
5000
V
IN
= 4.5V
V
IN
= 12V
V
IN
= 24V
V
IN
= 36V
1000 1500 2000 2500
LOAD CURRENT (mA)
CONDITIONS: PWM MODE
3000
3500
LINE AND LOAD REGULATION
3.310
V
IN
= 36V
3.305
V
IN
= 24V
toc04
LINE AND LOAD REGULATION
3.39
3.37
V
IN
= 12V
toc05
LINE AND LOAD REGULATION
3.310
V
IN
= 36V
V
IN
= 24V
3.305
toc06
V
IN
= 36V
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.300
3.295
3.290
3.285
3.280
V
IN
= 4.5V
V
IN
= 12V
3.35
3.33
3.31
3.29
3.27
3.25
V
IN
= 4.5V
OUTPUT VOLTAGE (V)
V
IN
= 24V
3.300
3.295
3.290
3.285
3.280
V
IN
= 12V
V
IN
= 4.5V
0
500
1000 1500 2000 2500 3000
LOAD CURRENT (mA)
CONDITIONS: PWM MODE
3500
0
500
1000 1500 2000 2500
LOAD CURRENT (mA)
CONDITIONS: PFM MODE
3000
3500
0
500
1000 1500 2000 2500
LOAD CURRENT (mA)
CONDITIONS: DCM MODE
3000
3500
SOFT-START/SHUTDOWN FROM EN/UVLO
toc07
SOFT-START WITH PRE-BIAS OF VOLTAGE 1.65V
toc08
V
EN/UVLO
5V/div
V
EN/UVLO
5V/div
V
OUT
2V/div
V
OUT
I
LX
2V/div
2A/div
I
LX
V
RESET
2ms/div
CONDITIONS: PWM MODE, 3.5A LOAD CURRENT
2A/div
5V/div
V
RESET
2ms/div
CONDITIONS: PWM MODE, 35mA LOAD CURRENT
5V/div
www.maximintegrated.com
Maxim Integrated │
4
MAX17633AEVKIT# Evaluation Kit
Evaluates: MAX17633
3.3V Output-Voltage Application
(V
IN
= 24V, L = 5.6μH (XAL5050-562ME), f
SW
= 500kHz, unless otherwise noted.)
MAX17633A EV Kit Performance Report (continued)
STEADY STATE PERFORMANCE
toc09
STEADY STATE PERFORMANCE
STEADY STATE PERFORMANCE
toc10
toc11
V
LX
20V/div
V
LX
20V/div
V
LX
20V/div
V
OUT
(AC-
COUPLED)
20mV/div
V
OUT
(AC-
10mV/div
V
OUT (AC-
COUPLED)
COUPLED)
50mV/div
I
LX
2µs/div
CONDITIONS: 3.5A LOAD CURRENT, PWM MODE
2A/div
I
LX
1µs/div
CONDITIONS: 35mA LOAD CURRENT, DCM MODE
0.5A/div
I
LX
40µs/div
CONDITIONS: 35mA LOAD CURRENT, PFM MODE
1A/div
LOAD TRANSIENT BETWEEN 0A AND 1.75A
toc12
LOAD TRANSIENT BETWEEN 1.75A AND 3.5A
toc13
LOAD TRANSIENT BETWEEN 0.035A AND 1.75A
toc14
V
OUT (AC-
COUPLED)
100mV/div
V
OUT (AC-
COUPLED)
100mV/div
V
OUT (AC-
COUPLED)
100mV/div
I
OUT
1A/div
I
OUT
2A/div
I
OUT
1A/div
100µs/div
CONDITIONS: PWM MODE
200µs/div
CONDITIONS: PWM MODE
400µs/div
CONDITIONS: PFM MODE
LOAD TRANSIENT BETWEEN 0.035A AND 1.75A
toc15
CLOSED LOOP BODE PLOT
40
toc16
100
90
80
V
OUT (AC-
COUPLED)
30
100mV/div
20
GAIN (dB)
0
-10
60
50
CROSSOVER
FREQUENCY = 56.4kHz
PHASE MARGIN = 61.9°
1k
40
I
OUT
1A/div
-20
-30
-40
200µs/div
CONDITIONS: DCM MODE
30
10k
100k
FREQUENCY (Hz)
CONDITIONS: 3.5A LOAD CURRENT, PWM MODE
www.maximintegrated.com
Maxim Integrated │ 5
PHASE (°)
10
70
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