EVALUATION KIT AVAILABLE
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
General Description
The MAX17504/MAX17504S high-efficiency, highvoltage, synchronously rectified step-down converter with
dual integrated MOSFETs operates over a 4.5V to 60V
input. It delivers up to 3.5A and 0.9V to 90% VIN output
voltage. Built-in compensation across the output voltage
range eliminates the need for external components. The
feedback (FB) regulation accuracy over -40°C to +125°C
is ±1.1%. The device is available in a compact (5mm x
5mm) TQFN lead (Pb)-free package with an exposed pad.
Simulation models are available.
The device features a peak-current-mode control
architecture with a MODE feature that can be used to
operate the device in pulse-width modulation (PWM),
pulse-frequency modulation (PFM), or discontinuous
mode (DCM) control schemes. PWM operation provides
constant frequency operation at all loads, and is useful
in applications sensitive to switching frequency. PFM
operation disables negative inductor current and
additionally skips pulses at light loads for high efficiency.
DCM features constant frequency operation down to
lighter loads than PFM mode, by not skipping pulses,
but only disabling negative inductor current at light loads.
DCM operation offers efficiency performance that lies
between PWM and PFM modes. The MAX17504S offers
a lower minimum on-time that allows for higher switching
frequencies and a smaller solution size.
A programmable soft-start feature allows users to reduce
input inrush current. The device also incorporates an
output enable/undervoltage lockout pin (EN/UVLO) that
allows the user to turn on the part at the desired inputvoltage level. An open-drain RESET pin provides a
delayed power-good signal to the system upon achieving
successful regulation of the output voltage.
Applications
●
●
●
●
●
●
Industrial Power Supplies
Distributed Supply Regulation
Base Station Power Supplies
Wall Transformer Regulation
High-Voltage Single-Board Systems
General-Purpose Point-of-Load
19-6844; Rev 3; 5/17
Benefits and Features
●● Eliminates External Components and Reduces Total Cost
• No Schottky-Synchronous Operation for High
Efficiency and Reduced Cost
• Internal compensation for Stable Operation at Any
Output Voltage
• All Ceramic Capacitor Solution: Ultra-Compact
Layout with as Few as Eight External Components
●● Reduce Number of DC-DC Regulators to Stock
• Wide 4.5V to 60V Input Voltage Range
• 0.9V to 90% VIN Output Voltage
• Delivers Up to 3.5A Over Temperature
• 100kHz to 2.2MHz Adjustable Frequency with
External Synchronization
• MAX17504S Allows Higher Frequency Of Operation
• Available in a 20-Pin, 5mm x 5mm TQFN Package
●● Reduce Power Dissipation
• Peak Efficiency > 90%
• PFM and DCM Modes for High Light-Load Efficiency
• Shutdown Current = 2.8FA (typ)
●● Operate Reliably
• Hiccup-Mode Current Limit and Autoretry Startup
• Built-In Output Voltage Monitoring—(Open-Drain
RESET Pin)
• Resistor Programmable EN/UVLO Threshold
• Adjustable Soft-Start and Pre-Biased Power-Up
• High Industrial -40°C to +125°C Ambient Operating
Temperature Range/-40°C to +150°C Junction
Temperature Range
Ordering Information appears at end of data sheet.
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Absolute Maximum Ratings (Note 1)
VIN to PGND..........................................................-0.3V to +65V
EN/UVLO to SGND................................................-0.3V to +65V
LX to PGND................................................-0.3V to (VIN + 0.3V)
BST to PGND.........................................................-0.3V to +70V
BST to LX..............................................................-0.3V to +6.5V
BST to VCC............................................................-0.3V to +65V
FB, CF, RESET, SS, MODE, SYNC,
RT to SGND......................................................-0.3V to +6.5V
VCC to SGND........................................................-0.3V to +6.5V
SGND to PGND.....................................................-0.3V to +0.3V
LX Total RMS Current.........................................................±5.6A
Output Short-Circuit Duration.....................................Continuous
Continuous Power Dissipation (TA = +70°C) (multilayer board)
TQFN (derate 33.3mW/°C above TA = +70°C).......2666.7mW
Junction Temperature.......................................................+150°C
Storage Temperature Range............................. -65NC to +160°C
Lead Temperature (soldering, 10s).................................. +300°C
Soldering Temperature (reflow)........................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Package Information
PACKAGE TYPE: 20 TQFN
Package Code
T2055+4
Outline Number
21-0140
Land Pattern Number
90-0009
THERMAL RESISTANCE, FOUR-LAYER BOARD
Junction to Ambient (θJA)
30°C/W
Junction to Case (θJC)
2°C/W
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board.
For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Note 1: Junction temperature greater than +125°C degrades operating lifetimes.
Electrical Characteristics
(VIN = VEN/UVLO = 24V, RRT = 40.2kI (500kHz), CVCC = 2.2µF, VPGND = VSGND = VMODE = VSYNC = 0V, LX = SS = RESET =
open, VBST to VLX = 5V, VFB = 1V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are
referenced to SGND, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
60
V
VEN/UVLO = 0V (shutdown mode)
2.8
4.5
VFB = 1V, MODE = RT= open
118
INPUT SUPPLY (VIN)
Input Voltage Range
Input Shutdown Current
VIN
IIN-SH
IQ_PFM
Input Quiescent Current
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4.5
VFB = 1V, MODE = open
162
IQ_DCM
DCM mode, VLX = 0.1V
1.16
IQ_PWM
Normal switching mode, fSW = 500kHz,
VFB = 0.8V
9.5
µA
1.8
mA
Maxim Integrated │ 2
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Electrical Characteristics (continued)
(VIN = VEN/UVLO = 24V, RRT = 40.2kI (500kHz), CVCC = 2.2µF, VPGND = VSGND = VMODE = VSYNC = 0V, LX = SS = RESET =
open, VBST to VLX = 5V, VFB = 1V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are
referenced to SGND, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
ENABLE/UVLO (EN/UVLO)
EN/UVLO Threshold
EN/UVLO Input Leakage Current
VENR
VEN/UVLO rising
1.19
1.215
1.24
VENF
VEN/UVLO falling
1.068
1.09
1.111
-50
0
+50
nA
4.75
5
5.25
V
26.5
54
100
mA
IEN
VEN/UVLO = 0V, TA = +25ºC
V
LDO
VCC Output Voltage Range
VCC
VCC Current Limit
IVCC-MAX
VCC Dropout
VCC-DO
6V < VIN < 60V, IVCC = 1mA
1mA ≤ IVCC ≤ 25mA
VCC = 4.3V, VIN = 6V
VIN = 4.5V, IVCC = 20mA
4.2
VCC_UVR
VCC rising
4.05
4.2
4.3
VCC_UVF
VCC falling
3.65
3.8
3.9
High-Side nMOS On-Resistance
RDS-ONH
ILX = 0.3A
165
325
mΩ
Low-Side nMOS On-Resistance
RDS-ONL
ILX = 0.3A
80
150
mΩ
ILX_LKG
VLX = VIN - 1V, VLX = VPGND + 1V,
TA = +25ºC
-2
+2
µA
VSS = 0.5V
4.7
5.3
µA
MODE = SGND or MODE = VCC
0.89
0.9
0.91
MODE = open
0.89
0.915
0.936
0 < VFB < 1V, TA = +25ºC
-50
VCC UVLO
V
V
POWER MOSFET AND BST DRIVER
LX Leakage Current
SOFT-START (SS)
Charging Current
ISS
5
FEEDBACK (FB)
FB Regulation Voltage
VFB_REG
FB Input Bias Current
IFB
+50
V
nA
MODE
MODE Threshold
VM-DCM
MODE = VCC (DCM mode)
VM-PFM
MODE = open (PFM mode)
VM-PWM
MODE = GND (PWM mode)
VCC 1.6
V
VCC/2
1.4
CURRENT LIMIT
Peak Current-Limit Threshold
Runaway Current-Limit Threshold
IPEAK-LIMIT
4.4
5.1
5.85
A
IRUNAWAY-LIMIT
4.9
5.7
6.7
A
0
+0.16
Valley Current-Limit Threshold
ISINK-LIMIT
PFM Current-Limit Threshold
IPFM
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MODE = open or MODE = VCC
-0.16
MODE = GND
MODE = open
-1.8
0.6
0.75
0.9
A
A
Maxim Integrated │ 3
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Electrical Characteristics (continued)
(VIN = VEN/UVLO = 24V, RRT = 40.2kI (500kHz), CVCC = 2.2µF, VPGND = VSGND = VMODE = VSYNC = 0V, LX = SS = RESET =
open, VBST to VLX = 5V, VFB = 1V, TA = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are
referenced to SGND, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
RRT = 210kΩ
90
100
110
RRT = 102kΩ
180
200
220
RRT = 40.2kΩ
475
500
525
RRT = 8.06kΩ
1950
2200
2450
RRT = OPEN
460
500
540
fSW set bt RRT
1.1 x
fSW
UNITS
RT AND SYNC
Switching Frequency
fSW
SYNC Frequency Capture Range
SYNC Pulse Width
SYNC Threshold
VFB Undervoltage Trip Level to
Cause Hiccup
1.4 x
fSW
50
VIH
VIL
0.8
HICCUP Timeout
0.56
(Note 3)
Minimum On-Time
tON-MIN
Minimum Off-Time
tOFF-MIN
0.58
0.6
32768
MAX17504
MAX17504S
55
140
LX Dead Time
RESET Output Level Low
IRESET = 1mA
RESET Output Leakage Current
TA = TJ = +25ºC, VRESET = 5.5V
-0.1
V
V
Cycles
135
ns
80
ns
160
ns
5
RESET
kHz
ns
2.1
VFB-HICF
kHz
ns
0.4
V
+0.1
µA
VOUT Threshold for RESET
Assertion
VFB-OKF
VFB falling
90.5
92
94
%
VOUT Threshold for RESET
Deassertion
VFB-OKR
VFB rising
93.8
95
97.2
%
RESET Deassertion Delay After FB
Reaches 95% Regulation
1024
Cycles
165
ºC
10
ºC
THERMAL SHUTDOWN
Thermal Shutdown Threshold
Temperature rising
Thermal Shutdown Hysteresis
Note 2: All limits are 100% tested at +25°C. Limits over temperature are guaranteed by design.
Note 3: See the Overcurrent Protection/HICCUP Mode section for more details.
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Maxim Integrated │ 4
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 5V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PWM MODE, FIGURE 5 CIRCUIT)
toc01
100
100
80
70
VIN = 48V
VIN = 36V
VIN = 24V
EFFICIENCY (%)
EFFICIENCY (%)
90
VIN = 12V
60
MAX17504 3.3V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PWM MODE, FIGURE 4 CIRCUIT)
toc01a
100
90
90
80
80
70
VIN = 24V
60
VIN = 36V
EFFICIENCY (%)
MAX17504 5V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PWM MODE, FIGURE 3 CIRCUIT)
VIN = 48V
VIN = 12V
50
40
MODE = SGND
0
500
VIN = 12V
60
1000 1500 2000 2500 3000 3500
30
LOAD CURRENT (mA)
VIN = 48V
50
50
40
VIN = 36V
VIN = 24V
70
toc02
40
MODE = SGND
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
MODE = SGND
0
500
1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
LOAD CURRENT (A)
MAX17504S 3.3V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PWM MODE, FIGURE 6 CIRCUIT)
toc02a
100
90
90
80
80
EFFICIENCY (%)
EFFICIENCY (%)
100
MAX17504 5V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PFM MODE, FIGURE 3 CIRCUIT)
70
VIN = 36V
60
VIN = 12V
50
VIN = 24V
VIN = 48V
VIN = 48V
VIN = 24V
60
VIN = 36V
VIN = 12V
50
40
40
MODE = OPEN
30
30
MODE = SGND
20
70
toc03
0.0
0.5
1.0
1.5
2.0
2.5
3.0
1
3.5
10
100
3500
1000
LOAD CURRENT (mA)
LOAD CURRENT (A)
MAX17504S 5V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PFM MODE, FIGURE 5 CIRCUIT)
100
toc03a
90
90
80
80
70
EFFICIENCY (%)
EFFICIENCY (%)
100
MAX17504 3.3V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PFM MODE, FIGURE 4 CIRCUIT)
VIN = 48V
60
VIN = 24V
VIN = 12V
VIN = 36V
VIN = 48V
60
VIN = 24V
VIN = 36V
VIN = 12V
40
40
MODE = OPEN
30
70
50
50
toc04
0.0
0.1
1.0
30
3.5
MODE = OPEN
1
10
100
1000
3500
LOAD CURRENT (mA)
LOAD CURRENT (A)
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Maxim Integrated │ 5
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 3.3V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(PFM MODE, FIGURE 6 CIRCUIT)
100
MAX17504 5V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(DCM MODE, FIGURE 3 CIRCUIT)
toc04a
100
MAX17504S 5V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(DCM MODE, FIGURE 5 CIRCUIT)
toc05
100
VIN = 48V
VIN = 48V
60
50
VIN = 12V
VIN = 24V
VIN = 36V
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
70
VIN = 24V
70
60
VIN = 12V
50
MODE = OPEN
0.0
0.1
30
3.5
1.0
VIN = 24V
70
VIN = 12V
60
50
40
30
20
40
40
VIN = 36V
80
VIN = 36V
80
80
30
90
90
90
MODE = VCC
1
10
100
10
1000
0
3500
LOAD CURRENT (mA)
MODE = VCC
0.0
0.1
100
MAX17504S 3.3V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(DCM MODE, FIGURE 6 CIRCUIT)
toc06
100
VIN = 48V
VIN = 24V
VIN = 12V
60
50
VIN = 24V
70
VIN = 12V
60
50
40
30
40
MODE = VCC
30
1
10
100
20
10
3500
1000
LOAD CURRENT (mA)
MODE = VCC
0.0
toc07a
5.00
5.07
4.99
5.06
5.05
4.98
VIN = 36V
5.04
5.03
5.02
5.01
VIN = 12V VIN = 48V
5.00
VIN = 24V
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1.0
MAX17504S 5V OUTPUT
LOAD AND LINE REGULATION
(PWM MODE, FIGURE 5 CIRCUIT)
toc07
5.08
0.1
LOAD CURRENT (A)
MAX17504 5V OUTPUT
LOAD AND LINE REGULATION
(PWM MODE, FIGURE 3 CIRCUIT)
VIN = 48V
VIN = 36V
4.97
4.96
4.95
4.94
VIN = 24V
VIN = 12V
4.93
4.99
4.98
toc06a
VIN = 36V
80
EFFICIENCY (%)
EFFICIENCY (%)
VIN = 36V
70
3.5
VIN = 48V
90
90
80
1.0
LOAD CURRENT (A)
LOAD CURRENT (A)
MAX17504 3.3V OUTPUT
EFFICIENCY vs. LOAD CURRENT
(DCM MODE, FIGURE 4 CIRCUIT)
toc05a
VIN = 48V
MODE = SGND
0
500
1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
4.92
4.91
MODE = SGND
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
LOAD CURRENT (A)
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Maxim Integrated │ 6
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 3.3V OUTPUT
LOAD AND LINE REGULATION
(PWM MODE, FIGURE 6 CIRCUIT)
MAX17504 3.3V OUTPUT
LOAD AND LINE REGULATION
(PWM MODE, FIGURE 4 CIRCUIT)
toc08
3.36
5.4
VIN = 48V
3.32
3.31
3.30
3.29
VIN = 36V
VIN = 12V
3.28
VIN = 24V
3.27
0
500
VIN = 48V
VIN = 24V
3.37
3.36
3.35
VIN = 12V
5.2
VIN = 36V
5.1
5.0
4.9
4.8
3.32
LOAD CURRENT (mA)
4.5
MODE = SGND
0.0
0.5
1.0
1.5
2.0
2.5
3.0
VIN = 48V
VIN = 36V
4.6
3.33
1000 1500 2000 2500 3000 3500
VIN = 12V
4.7
3.34
MODE = SGND
VIN = 24V
5.3
3.38
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.33
toc09
5.5
3.39
3.34
3.26
toc08a
3.40
3.35
MAX17504 5V OUTPUT
LOAD AND LINE REGULATION
(PFM MODE, FIGURE 3 CIRCUIT)
MODE = OPEN
0
500
1000 1500 2000 2500 3000 3500
3.5
LOAD CURRENT (mA)
LOAD CURRENT (A)
MAX17504 3.3V OUTPUT
LOAD AND LINE REGULATION
(PFM MODE, FIGURE 4 CIRCUIT)
MAX17504S 5V OUTPUT
LOAD AND LINE REGULATION
(PFM MODE, FIGURE 5 CIRCUIT)
toc09a
5.25
5.20
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.5
VIN = 48V
5.15
5.10
VIN = 12V
5.05
5.00
4.95
4.90
VIN = 24V
VIN =36V
4.85
4.80
4.75
0.5
1.0
1.5
2.0
2.5
VIN = 12V
3.4
3.3
3.2
VIN = 24V
3.1
3.0
MODE = OPEN
0.0
toc10
3.6
3.0
VIN = 48V
VIN = 36V
MODE = OPEN
0
500
1000 1500 2000 2500 3000 3500
3.5
LOAD CURRENT (mA)
LOAD CURRENT (A)
MAX17504S 3.3V OUTPUT
LOAD AND LINE REGULATION
(PFM MODE, FIGURE 6 CIRCUIT)
3.60
SWITCHING FREQUENCY (kHz)
VIN = 48V
3.50
VIN = 36V
3.45
3.40
VIN = 24V
3.35
3.30
VIN = 12V
2000
1800
1600
1400
1200
1000
800
600
400
3.25
3.20
toc11
2400
2200
3.55
OUTPUT VOLTAGE (V)
SWITCHING FREQUENCY
vs. RT RESISTANCE
toc10a
200
MODE = OPEN
0.0
0.5
1.0
1.5
2.0
LOAD CURRENT (A)
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2.5
3.0
0
3.5
0
20
40
60
80
100
RRT (kΩ)
Maxim Integrated │ 7
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 5V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO
(3.5A LOAD CURRENT, FIGURE 5 CIRCUIT)
MAX17504 5V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO
(3.5A LOAD CURRENT, FIGURE 3 CIRCUIT)
toc12a
toc12
VEN/UVLO
2V/div
VEN/UVLO
5V/div
VOUT
2V/div
VOUT
2V/div
IOUT
2A/div
5V/div
VRESET
MODE = SGND
IOUT
VRESET
2A/div
MODE = SGND
5V/div
2ms/div
1ms/div
MAX17504S 3.3V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO
(3.5A LOAD CURRENT, FIGURE 6 CIRCUIT)
MAX17504 3.3V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO,
(3.5A LOAD CURRENT, FIGURE 4 CIRCUIT)
toc13a
toc13
VEN/UVLO
2V/div
VOUT
VEN/UVLO
5V/div
2V/div
VOUT
2V/div
1A/div
IOUT
2A/div
IOUT
VRESET
5V/div
VRESET
5V/div
MODE = SGND
MODE = SGND
2mS/div
1ms/div
MAX17504 5V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO
(PFM MODE, 5mA LOAD CURRENT, FIGURE 3 CIRCUIT)
MAX17504S 5V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO
(PFM MODE, 5mA LOAD CURRENT, FIGURE 5 CIRCUIT)
toc14a
toc14
MODE = OPEN
VEN/UVLO
2V/div
VOUT
1V/div
VRESET
5V/div
2ms/div
www.maximintegrated.com
VEN/UVLO
5V/div
1V/div
VOUT
MODE = OPEN
5V/div
2mS/div
Maxim Integrated │ 8
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
toc15a
toc15
VEN/UVLO
MAX17504 5V OUTPUT
SOFT-START WITH 2.5V PREBIAS
(PWM MODE, FIGURE 3 CIRCUIT)
MAX17504S 3.3V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO
(PFM MODE, 5mA LOAD CURRENT, FIGURE 6 CIRCUIT)
MAX17504 3.3V OUTPUT
SOFT-START/SHUTDOWN FROM EN/UVLO
(PFM MODE, 5mA LOAD CURRENT, FIGURE 4 CIRCUIT)
VEN/UVLO
2V/div
5V/div
VEN/UVLO
toc16
2V/div
2V/div
VRESET
1V/div
VOUT
1V/div
VOUT
5V/div
5V/div
MODE = OPEN
VOUT
5V/div
VRESET
MODE = SGND
MODE = OPEN
2ms/div
1ms/div
2ms/div
MAX17504S 5V OUTPUT
SOFT-START WITH 2.5V PREBIAS
(PWM MODE, FIGURE 5 CIRCUIT)
MAX17504 3.3V OUTPUT
SOFT-START WITH 2.5V PREBIAS
(PFM MODE, FIGURE 4 CIRCUIT)
toc16a
toc17
5V/div
VEN/UVLO
1V/div
VEN/UVLO
2V/div
1V/div
VOUT
VRESET
VOUT
5V/div
MODE = OPEN
MODE = SGND
VRESET
1ms/div
5V/div
1mS/div
MAX17504S 3.3V OUTPUT
SOFT-START WITH 2.5V PREBIAS
(PWM MODE, FIGURE 6 CIRCUIT)
MAX17504 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(3.5A LOAD CURRENT, FIGURE 3 CIRCUIT)
toc18
toc17a
VEN/UVLO
VOUT
(AC)
20mV/div
VLX
10V/div
5V/div
1V/div
ILX
VOUT
2A/div
5V/div
MODE = SGND
VRESET
1μs/div
1mS/div
www.maximintegrated.com
Maxim Integrated │ 9
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(3.5A LOAD CURRENT, FIGURE 5 CIRCUIT)
MAX17504S 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(NO LOAD CURRENT, FIGURE 5 CIRCUIT)
MAX17504 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(PWM MODE, NO LOAD, FIGURE 3 CIRCUIT)
toc18a
toc19a
toc19
MODE = SGND
VOUT
(AC)
VOUT
(AC)
VOUT
(AC)
50mV/div
20mV/div
10V/div
VLX
10V/div
VLX
MODE = SGND
20mV/div
ILX
500mA/div
10V/div
VLX
1A/div
MODE = SGND
ILX
ILX
1μs/div
2A/div
1µs/div
1µS/div
MAX17504S 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(PFM MODE, 25mA LOAD CURRENT, FIGURE 5 CIRCUIT)
MAX17504 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(PFM MODE, 25mA LOAD, FIGURE 3 CIRCUIT)
toc20
toc20a
MODE = OPEN
VOUT
(AC)
100mV/div
VLX
10V/div
ILX
VOUT
(AC)
100mV/div
VLX
10V/div
ILX
500mA/div
500mA/div
MODE = OPEN
10μs/div
4μs/div
MAX17504 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(DCM MODE, 25mA LOAD, FIGURE 3 CIRCUIT)
toc21
MAX17504S 5V OUTPUT
STEADY-STATE SWITCHING WAVEFORMS
(DCM MODE, 150mA LOAD CURRENT, FIGURE 5 CIRCUIT)
toc21a
MODE = VCC
VOUT
(AC)
20mV/div
VOUT
(AC)
MODE = VCC
20mV/div
10V/div
VLX
VLX
ILX
10V/div
200mA/div
1μs/div
500mA/div
ILX
1μs/div
www.maximintegrated.com
Maxim Integrated │ 10
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 5V OUTPUT
LOAD CURRENT STEPPED FROM 1.75A TO 3.5A
(PWM MODE, FIGURE 5 CIRCUIT)
MAX17504 5V OUTPUT
LOAD CURRENT STEPPED FROM 1.7`5A TO 3.5A
(PWM MODE, FIGURE 3 CIRCUIT)
toc22
VOUT
(AC)
toc22a
100mV/div
VOUT
AC
IOUT
100mV/div
2A/div
MODE = SGND
ILX
2A/div
40μs/div
MODE = SGND
100μS/div
MAX17504 3.3V OUTPUT
LOAD CURRENT STEPPED FROM 1.75A TO 3.5A
(PWM MODE, FIGURE 4 CIRCUIT)
toc23
MAX17504S 3.3V OUTPUT
LOAD CURRENT STEPPED FROM 1.75A TO 3.5A
(PWM MODE, FIGURE 6 CIRCUIT)
toc23a
VOUT
(AC)
100mV/div
VOUT
AC
100mV/div
2A/div
IOUT
MODE = SGND
ILX
100μs/div
2A/div
MODE = SGND
100μS/div
MAX17504 5V OUTPUT
LOAD CURRENT STEPPED FROM NO LOAD TO 1.75A
(PWM MODE, FIGURE 3 CIRCUIT)
MAX17504S 5V OUTPUT
LOAD CURRENT STEPPED FROM NO LOAD TO 1.75A
(PWM MODE, FIGURE 5 CIRCUIT)
toc24a
toc24
VOUT
(AC)
100mV/div
IOUT
VOUT
AC
100mV/div
1A/div
MODE = SGND
ILX
1A/div
MODE = SGND
40μs/div
100μS/div
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Maxim Integrated │ 11
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504 3.3V OUTPUT
LOAD CURRENT STEPPED FROM NO LOAD TO 1.75A
(PWM MODE, FIGURE 4 CIRCUIT)
MAX17504S 3.3V OUTPUT
LOAD CURRENT STEPPED FROM NO LOAD TO 1.75A
(PWM MODE, FIGURE 6 CIRCUIT)
toc25a
toc25
VOUT
(AC)
100mV/div
VOUT
AC
100mV/div
1A/div
IOUT
MODE = SGND
ILX
1A/div
MODE = SGND
100μs/div
100μS/div
MAX17504 5V OUTPUT
LOAD CURRENT STEPPED FROM 5mA TO 1.75A
(PFM MODE, FIGURE 3 CIRCUIT)
MAX17504S 5V OUTPUT
LOAD CURRENT STEPPED FROM 5MA TO 1.75A
(PFM MODE, FIGURE 5 CIRCUIT)
toc26
VOUT
(AC)
toc26a
100mV/div
VOUT
AC
100mV/div
1A/div
IOUT
MODE = OPEN
1A/div
ILX
2ms/div
MODE = OPEN
1mS/div
MAX17504 3.3V OUTPUT
LOAD CURRENT STEPPED FROM 5mA TO 1.75A
(PFM MODE, FIGURE 4 CIRCUIT)
toc27
VOUT
(AC)
toc27a
100mV/div
IOUT
MAX17504S 3.3V OUTPUT
LOAD CURRENT STEPPED FROM 5MA TO 1.75A
(PFM MODE, FIGURE 6 CIRCUIT)
VOUT
AC
100mV/div
1A/div
MODE = OPEN
ILX
1A/div
MODE = OPEN
2ms/div
2mS/div
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Maxim Integrated │ 12
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 5V OUTPUT
LOAD CURRENT STEPPED FROM 50mA TO 1.75A
(DCM MODE, FIGURE 5 CIRCUIT)
MAX17504 5V OUTPUT
LOAD CURRENT STEPPED FROM 50mA TO 1.75A
(DCM MODE, FIGURE 3 CIRCUIT)
toc28
VOUT
(AC)
toc28a
100mV/div
VOUT (AC)
100mV/div
1A/div
IOUT
MODE = VCC
1A/div
IOUT
200μs/div
MODE = VCC
200μs/div
MAX17504S 3.3V OUTPUT
LOAD CURRENT STEPPED FROM 50mA TO 1.75A
(DCM MODE, FIGURE 6 CIRCUIT)
MAX17504 3.3V OUTPUT
LOAD CURRENT STEPPED FROM 50mA TO 1.75A
(DCM MODE, FIGURE 4 CIRCUIT)
toc29
VOUT
(AC)
toc29a
100mV/div
IOUT
VOUT (AC)
100mV/div
1A/div
MODE = VCC
IOUT
1A/div
200μs/div
MODE = VCC
200μs/div
MAX17504S 5V OUTPUT
OVERLOAD PROTECTION
(FIGURE 5 CIRCUIT)
MAX17504 5V OUTPUT
OVERLOAD PROTECTION
(FIGURE 3 CIRCUIT)
toc30a
toc30
VOUT
2V/div
50mV/div
VOUT
1A/div
IOUT
20ms/div
www.maximintegrated.com
IOUT
1A/div
10ms/div
Maxim Integrated │ 13
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Typical Operating Characteristics (continued)
(VIN = VEN/UVLO = 24V, VPGND = VSGND = 0V, CVIN = 2 x 2.2µF, CVCC = 2.2µF, CBST = 0.1µF, CSS = 12,000pF, RT = MODE = open, TA = TJ
= -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to SGND, unless otherwise noted.)
MAX17504S 5V OUTPUT
APPLICATION OF EXTERNAL CLOCK AT 1.2MHz,
(FIGURE 5 CIRCUIT)
toc31a
MAX17504 5V OUTPUT
APPLICATION OF EXTERNAL CLOCK AT 700kHz
(FIGURE 3 CIRCUIT)
toc31
VLX
10V/div
VSYNC
2V/div
VLX
10V/div
2V/div
MODE = SGND
MODE = SGND
2μs/div
2μs/div
MAX17504 5V OUTPUT
BODE PLOT
(3.5A LOAD CURRENT, FIGURE 3 CIRCUIT)
toc32
60
PHASE
GAIN
40
0
20
-10
0
-20
0
CROSSOVER FREQUENCY = 86kHz
PHASE MARGIN = 58.9°
-60
103
FREQUENCY (Hz)
toc33
GAIN (dB)
40
0
20
-10
0
CROSSOVER FREQUENCY = 52.7KHz
PHASE MARGIN = 62.4°
GAIN
0
-20
-20
CROSSOVER FREQUENCY = 82.3kHz
PHASE MARGIN = 59.4°
-40
-60
100K
50
0
PHASE (°)
GAIN
10K
PHASE
80
60
-40
1K
20
100
PHASE
20
-20
100
GAIN (dB)
40
30
-30
toc33a
40
140
120
50
10
105
104
FREQUENCY (Hz)
MAX17504S 3.3V OUTPUT
BODE PLOT
(3.5A LOAD CURRENT, FIGURE 6 CIRCUIT)
MAX17504 3.3V OUTPUT
BODE PLOT
(3.5A LOAD CURRENT, FIGURE 4 CIRCUIT)
60
-50
-30
100K
10K
GAIN
0
-20
-40
-40
50
10
-10
-20
CROSSOVER FREQUENCY = 48.4kHz
PHASE MARGIN = 62.3°
1K
PHASE
20
GAIN (dB)
60
-30
100
80
20
10
toc32a
30
100
40
30
GAIN (dB)
40
140
120
50
MAX17504S 5V OUTPUT
4 BODE PLOT
(3.5A LOAD CURRENT, FIGURE 5 CIRCUIT)
-50
-40
103
104
105
FREQUENCY (Hz)
FREQUENCY (Hz)
www.maximintegrated.com
Maxim Integrated │ 14
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
PGND
SGND
VCC
MODE
TOP VIEW
PGND
Pin Configuration
15
14
13
12
11
PGND 16
LX 17
MAX17504/
MAX17504S
LX 18
LX 19
3
4
5
RESET
2
EN/UVLO
VIN
1
VIN
+
VIN
BST 20
10
RT
9
FB
8
CF
7
SS
6
SYNC
TQFN
5mm × 5mm
* EXPOSED PAD (CONNECT TO SIGNAL GROUND).
Pin Description
PIN
NAME
FUNCTION
1, 2, 3
VIN
Power-Supply Input. 4.5V to 60V input supply range. Connect the VIN pins together. Decouple to PGND
with two 2.2µF capacitors; place the capacitors close to the VIN and PGND pins. Refer to the MAX17504/
MAX17504S EV kit data sheet for a layout example.
4
EN/UVLO
Enable/Undervoltage Lockout. Drive EN/UVLO high to enable the output voltage. Connect to the
center of the resistor-divider between VIN and SGND to set the input voltage at which the MAX17504/
MAX17504S turns on. Pull up to VIN for always on operation.
5
RESET
Open-Drain RESET Output. The RESET output is driven low if FB drops below 92% of its set value.
RESET goes high 1024 clock cycles after FB rises above 95% of its set value.
6
SYNC
7
SS
Soft-Start Input. Connect a capacitor from SS to SGND to set the soft-start time.
8
CF
At switching frequencies lower than 500kHz, connect a capacitor from CF to FB. Leave CF open if the
switching frequency is equal to or more than 500kHz. See the Loop Compensation section for more
details.
9
FB
Feedback Input. Connect FB to the center tap of an external resistor-divider from the output to SGND to
set the output voltage. See the Adjusting Output Voltage section for more details.
10
RT
Connect a resistor from RT to SGND to set the regulator’s switching frequency. Leave RT open for the
default 500kHz frequency. See the Setting the Switching Frequency (RT) section for more details.
MODE
MODE configures the MAX17504/MAX17504S to operate in PWM, PFM or DCM modes of operation.
Leave MODE unconnected for PFM operation (pulse skipping at light loads). Connect MODE to SGND
for constant-frequency PWM operation at all loads. Connect MODE to VCC for DCM operation. See the
MODE Setting section for more details.
11
www.maximintegrated.com
The device can be synchronized to an external clock using this pin. See the External Frequency
Synchronization section for more details.
Maxim Integrated │ 15
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Pin Description (continued)
PIN
NAME
FUNCTION
12
VCC
13
SGND
Analog Ground
14, 15, 16
PGND
Power Ground. Connect the PGND pins externally to the power ground plane. Connect the SGND and
PGND pins together at the ground return path of the VCC bypass capacitor. Refer to the MAX17504/
MAX17504S EV kit data sheet for a layout example.
17, 18, 19
LX
20
BST
—
EP
5V LDO Output. Bypass VCC with a 2.2µF ceramic capacitance to SGND.
Switching Node. Connect LX pins to the switching side of the inductor.
Boost Flying Capacitor. Connect a 0.1µF ceramic capacitor between BST and LX.
Exposed pad. Connect to the SGND pin. Connect to a large copper plane below the IC to improve heat
dissipation capability. Add thermal vias below the exposed pad. Refer to the MAX17504/MAX17504S EV
kit data sheet for a layout example.
Block Diagram
VCC
5V
BST
MAX17504/MAX17504S
LDO
VIN
SGND
CURRENT-SENSE
LOGIC
EN/UVLO
LX
PWM/
PFM/
HICCUP
LOGIC
HICCUP
1.215V
RT
PGND
OSCILLATOR
SYNC
CF
FB
VCC
SS
SWITCHOVER
LOGIC
VBG = 0.9V
SLOPE
COMPENSATION
5µA
FB
HICCUP
www.maximintegrated.com
MODE
SELECTION
LOGIC
ERROR AMPLIFIER/
LOOP COMPENSATION
EN/UVLO
MODE
RESET
RESET
LOGIC
Maxim Integrated │ 16
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Detailed Description
The MAX17504/MAX17504S high-efficiency, high-voltage,
synchronously rectified step-down converter with dual
integrated MOSFETs operates over a 4.5V to 60V input.
It delivers up to 3.5A and 0.9V to 90% VIN output voltage.
Built-in compensation across the output voltage range
eliminates the need for external components. The feedback
(FB) regulation accuracy over -40°C to +125°C is ±1.1%.
The device features a peak-current-mode control
architecture. An internal transconductance error
amplifier produces an integrated error voltage at an
internal node that sets the duty cycle using a PWM
comparator, a high-side current-sense amplifier, and a
slope-compensation generator. At each rising edge of
the clock, the high-side MOSFET turns on and remains
on until either the appropriate or maximum duty cycle
is reached, or the peak current limit is detected. During
the high-side MOSFET’s on-time, the inductor current
ramps up. During the second half of the switching
cycle, the high-side MOSFET turns off and the low-side
MOSFET turns on. The inductor releases the stored
energy as its current ramps down and provides current
to the output.
The device features a MODE pin that can be used to operate
the device in PWM, PFM, or DCM control schemes. The
device integrates adjustable-input undervoltage lockout,
adjustable soft-start, open RESET, and external frequency
synchronization features. The MAX17504S offers a
lower minimum on-time that allows for higher switching
frequencies and a smaller solution size.
Mode Selection (MODE)
The logic state of the MODE pin is latched when VCC
and EN/UVLO voltages exceed the respective UVLO
rising thresholds and all internal voltages are ready to
allow LX switching. If the MODE pin is open at power-up,
the device operates in PFM mode at light loads. If the
MODE pin is grounded at power-up, the device operates
in constant-frequency PWM mode at all loads. Finally,
if the MODE pin is connected to VCC at power-up, the
device operates in constant-frequency DCM mode at light
loads. State changes on the MODE pin are ignored during
normal operation.
PWM Mode Operation
In PWM mode, the inductor current is allowed to go negative.
PWM operation provides constant frequency operation at
all loads, and is useful in applications sensitive to switching
frequency. However, the PWM mode of operation gives lower
efficiency at light loads compared to PFM and DCM modes
of operation.
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PFM Mode Operation
PFM mode of operation disables negative inductor current
and additionally skips pulses at light loads for high
efficiency. In PFM mode, the inductor current is forced to
a fixed peak of 750mA every clock cycle until the output
rises to 102.3% of the nominal voltage. Once the output
reaches 102.3% of the nominal voltage, both the high-side
and low-side FETs are turned off and the device enters
hibernate operation until the load discharges the output to
101.1% of the nominal voltage. Most of the internal blocks
are turned off in hibernate operation to save quiescent
current. After the output falls below 101.1% of the nominal
voltage, the device comes out of hibernate operation,
turns on all internal blocks, and again commences the
process of delivering pulses of energy to the output until it
reaches 102.3% of the nominal output voltage.
The advantage of the PFM mode is higher efficiency at
light loads because of lower quiescent current drawn from
supply. The disadvantage is that the output-voltage ripple
is higher compared to PWM or DCM modes of operation
and switching frequency is not constant at light loads.
DCM Mode Operation
DCM mode of operation features constant frequency
operation down to lighter loads than PFM mode, by not
skipping pulses but only disabling negative inductor
current at light loads. DCM operation offers efficiency
performance that lies between PWM and PFM modes.
Linear Regulator (VCC)
An internal linear regulator (VCC) provides a 5V nominal
supply to power the internal blocks and the low-side
MOSFET driver. The output of the linear regulator (VCC)
should be bypassed with a 2.2µF ceramic capacitor
to SGND. The MAX17504/MAX17504S employs an
undervoltage lockout circuit that disables the internal
linear regulator when VCC falls below 3.8V (typ).
Setting the Switching Frequency (RT)
The switching frequency of the MAX17504/MAX17504S
can be programmed from 100kHz to 2.2MHz by using
a resistor connected from RT to SGND. The switching
frequency (fSW) is related to the resistor connected at the
RT pin (RRT) by the following equation:
R RT ≅
21× 10 3
f SW
−
1.7
where RRT is in kΩ and fSW is in kHz. Leaving the RT pin
open causes the device to operate at the default switching
frequency of 500kHz. See Table 1 for RT resistor values
for a few common switching frequencies.
Maxim Integrated │ 17
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Table 1. Switching Frequency vs. RT Resistor
SWITCHING FREQUENCY (kHz)
RT RESISTOR (kΩ)
500
100
200
400
1000
2200
OPEN
210
102
49.9
19.1
8.06
Operating Input Voltage Range
The minimum and maximum operating input voltages for
a given output voltage should be calculated as follows:
VIN(MIN) =
VOUT + (I OUT(MAX) × (R DCR + 0.15))
1- (f SW(MAX) × t OFF(MAX) )
+ (I OUT(MAX) × 0.175)
VIN(MAX) =
VOUT
f SW(MAX) × t ON(MIN)
where VOUT is the steady-state output voltage, IOUT(MAX)
is the maximum load current, RDCR is the DC resistance
of the inductor, fSW(MAX) is the maximum switching
frequency, tOFF(MAX) is the worst-case minimum switch
off-time (160ns), and tON(MIN) is the worst-case minimum
switch on-time (135ns for the MAX17504, 80ns for the
MAX17504S).
External Frequency Synchronization (SYNC)
The internal oscillator of the MAX17504/MAX17504S can
be synchronized to an external clock signal on the SYNC
pin. The external synchronization clock frequency must
be between 1.1 x fSW and 1.4 x fSW, where fSW is the
frequency programmed by the RT resistor. The minimum
external clock pulse-width high should be greater than
50ns. See the RT and SYNC section in the Electrical
Characteristics table for details.
Overcurrent Protection/HICCUP Mode
The MAX17504/MAX17504S is provided with a robust
overcurrent protection scheme that protects the device
under overload and output short-circuit conditions. A
cycle-by-cycle peak current limit turns off the high-side
MOSFET whenever the high-side switch current exceeds
an internal limit of 5.1A (typ). A runaway current limit on
the high-side switch current at 5.7A (typ) protects the
www.maximintegrated.com
device under high input voltage, short-circuit conditions
when there is insufficient output voltage available to
restore the inductor current that was built up during the
ON period of the step-down converter. One occurrence
of the runaway current limit triggers a hiccup mode. In
addition, if due to a fault condition, feedback voltage
drops to 0.58V (typ) anytime after soft-start is complete,
hiccup mode is triggered. In hiccup mode, the converter
is protected by suspending switching for a hiccup timeout
period of 32,768 clock cycles. Once the hiccup timeout
period expires, soft-start is attempted again. Note that
when soft-start is attempted under an overload condition,
if feedback voltage does not exceed 0.58V, the device
switches at half the programmed switching frequency.
Hiccup mode of operation ensures low power dissipation
under output short-circuit conditions.
RESET Output
The MAX17504/MAX17504S includes a RESET
comparator to monitor the output voltage. The opendrain RESET output requires an external pullup resistor.
RESET goes high (high-impedance) 1024 switching
cycles after the regulator output increases above 95%
of the designed nominal regulated voltage. RESET goes
low when the regulator output voltage drops to below 92%
of the nominal regulated voltage. RESET also goes low
during thermal shutdown.
Prebiased Output
When the MAX17504/MAX17504S starts into a prebiased
output, both the high-side and the low-side switches are
turned off so that the converter does not sink current from
the output. High-side and low-side switches do not start
switching until the PWM comparator commands the first
PWM pulse, at which point switching commences. The
output voltage is then smoothly ramped up to the target
value in alignment with the internal reference.
Thermal-Shutdown Protection
Thermal-shutdown protection limits total power dissipation
in the MAX17504/MAX17504S. When the junction
temperature of the device exceeds +165°C, an on-chip
thermal sensor shuts down the device, allowing the device
to cool. The thermal sensor turns the device on again
after the junction temperature cools by 10°C. Soft-start
resets during thermal shutdown. Carefully evaluate the
total power dissipation (see the Power Dissipation section)
to avoid unwanted triggering of the thermal shutdown in
normal operation.
Maxim Integrated │ 18
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Applications Information
Input Capacitor Selection
The input filter capacitor reduces peak currents drawn
from the power source and reduces noise and voltage
ripple on the input caused by the circuit’s switching.
The input capacitor RMS current requirement (IRMS) is
defined by the following equation:
=
IRMS I OUT(MAX) ×
VOUT × (VIN - VOUT )
VIN
where, IOUT(MAX) is the maximum load current. IRMS has
a maximum value when the input voltage equals twice
the output voltage (VIN = 2 x VOUT), so IRMS(MAX) =
IOUT(MAX)/2.
Choose an input capacitor that exhibits less than +10°C
temperature rise at the RMS input current for optimal
long-term reliability. Use low-ESR ceramic capacitors with
high ripple current capability at the input. X7R capacitors
are recommended in industrial applications for their
temperature stability. Calculate the input capacitance
using the following equation:
C IN =
I OUT(MAX) × D × (1- D)
η × f SW × ∆VIN
where D = VOUT/VIN is the duty ratio of the controller,
fSW is the switching frequency, ΔVIN is the allowable input
voltage ripple, and E is the efficiency.
In applications where the source is located distant
from the MAX17504/MAX17504S input, an electrolytic
capacitor should be added in parallel to the ceramic
capacitor to provide necessary damping for potential
oscillations caused by the inductance of the longer input
power path and input ceramic capacitor.
Inductor Selection
Three key inductor parameters must be specified for
operation with the MAX17504/MAX17504S: inductance
value (L), inductor saturation current (ISAT), and DC
resistance (RDCR). The switching frequency and output
voltage determine the inductor value as follows:
L=
VOUT
f SW
where VOUT and fSW are nominal values.
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Select a low-loss inductor closest to the calculated
value with acceptable dimensions and having the lowest
possible DC resistance. The saturation current rating
(ISAT) of the inductor must be high enough to ensure that
saturation can occur only above the peak current-limit
value of 5.1A.
Output Capacitor Selection
X7R ceramic output capacitors are preferred due to their
stability over temperature in industrial applications. The
output capacitors are usually sized to support a step load
of 50% of the maximum output current in the application,
so the output voltage deviation is contained to 3% of the
output voltage change. The minimum required output
capacitance can be calculated as follows:
C OUT=
1 I STEP × t RESPONSE
×
2
∆VOUT
t RESPONSE ≅ (
0.33
1
+
)
fC
f sw
where ISTEP is the load current step, tRESPONSE is the
response time of the controller, DVOUT is the allowable
output voltage deviation, fC is the target closed-loop
crossover frequency, and fSW is the switching frequency.
For the MAX17504, select fC to be 1/9th of fSW if the
switching frequency is less than or equal to 500kHz. If the
switching frequency is more than 500kHz, select fC to be
55kHz. For the MAX17504S, select fC to be 1/10th of fSW
if the switching frequency is less than or equal to 1MHz.
If the switching frequency is more than 1MHz, select fC
to be 100kHz.
Derating of ceramic capacitors with DC-voltage must be
considered while selecting the output capacitor. Derating
curves are available from all major ceramic capacitor
vendors.
VIN
R1
EN/UVLO
R2
SGND
Figure 1. Setting the Input Undervoltage Lockout
Maxim Integrated │ 19
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Soft-Start Capacitor Selection
The MAX17504/MAX17504S implements adjustable softstart operation to reduce inrush current. A capacitor
connected from the SS pin to SGND programs the
soft-start time. The selected output capacitance (CSEL)
and the output voltage (VOUT) determine the minimum
required soft-start capacitor as follows:
CSS ≥ 28 x 10-6 x CSEL x VOUT
The soft-start time (tSS) is related to the capacitor
connected at SS (CSS) by the following equation:
tSS = CSS/(5.55 x 10-6)
For example, to program a 2ms soft-start time, a 12nF
capacitor should be connected from the SS pin to SGND.
Setting the Input Undervoltage Lockout Level
The MAX17504/MAX17504S offers an adjustable input
undervoltage lockout level. Set the voltage at which
MAX17504/MAX17504S turns ON, with a resistive voltagedivider connected from VIN to SGND. Connect the center
node of the divider to EN/UVLO.
Choose R1 to be 3.3MI and then calculate R2 as follows:
R2 =
R1× 1.215
(VINU - 1.215)
where VINU is the voltage at which the MAX17504/
MAX17504S is required to turn ON. Ensure that VINU is
higher than 0.8 x VOUT. If the EN/UVLO pin is driven from
an external signal source, a series resistance of minimum
1kΩ is recommended to be placed between the signal
source output and the EN/UVLO pin, to reduce voltage
ringing on the line.
capacitor (VOUT) to SGND (see Figure 2). Connect the
center node of the divider to the FB pin. Use the following
procedure to choose the resistive voltage-divider values:
Calculate resistor R3 from the output to FB as follows:
R3 =
216 × 10 3
f C × C OUT
where R3 is in kI, crossover frequency fC is in kHz,
and output capacitor COUT is in µF. For the MAX17504,
choose fC to be 1/9th of the switching frequency, fSW, if
the switching frequency is less than or equal to 500kHz.
If the switching frequency is more than 500kHz, select fC
to be 55kHz. For the MAX17504S, select fC to be 1/10th
of fSW if the switching frequency is less than or equal
to 1MHz. If the switching frequency is more than 1MHz,
select fC to be 100kHz.
Calculate resistor R4 from FB to SGND as follows:
R4 =
R3 × 0.9
(VOUT - 0.9)
Table 2. C6 Capacitor Value at Various
Switching Frequencies
SWITCHING FREQUENCY RANGE (kHz)
C6 (pF)
200 to 300
2.2
300 to 400
1.2
400 to 500
0.75
Loop Compensation
The MAX17504/MAX17504S is internally loop
compensated. However, if the switching frequency is less
than 500kHz, connect a 0402 capacitor, C6, between the
CF pin and the FB pin. Use Table 2 to select the value
of C6.
Adjusting Output Voltage
Set the output voltage with a resistive voltage-divider
connected from the positive terminal of the output
VOUT
R3
FB
R4
SGND
Figure 2. Setting the Output Voltage
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Maxim Integrated │ 20
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Power Dissipation
At a particular operating condition, the power losses that
lead to temperature rise of the part are estimated as
follows:
1
PLOSS =
(POUT × ( - 1)) - I OUT 2 × R DCR
η
(
)
P=
OUT VOUT × I OUT
where POUT is the total output power, η is the efficiency
of the converter, and RDCR is the DC resistance of the
inductor. (See the Typical Operating Characteristics for more
information on efficiency at typical operating conditions).
For a multilayer board, the thermal performance metrics
for the package are given below:
θ JA = 30°C W
θ JC =2°C W
The junction temperature of the MAX17504/MAX17504S
can be estimated at any given maximum ambient
temperature (TA_MAX) from the equation below:
TJ_MAX
= T A _MAX + (θ JA × PLOSS )
If the application has a thermal management system
that ensures that the exposed pad of the MAX17504/
MAX17504S is maintained at a given temperature (TEP_
MAX) by using proper heat sinks, then the junction
temperature of the MAX17504/MAX17504S can be
estimated at any given maximum ambient temperature
from the equation below:
T=
J_MAX TEP_MAX + (θ JC × PLOSS )
PCB Layout Guidelines
All connections carrying pulsed currents must be very
short and as wide as possible. The inductance of these
connections must be kept to an absolute minimum due to
the high di/dt of the currents. Since inductance of a current
carrying loop is proportional to the area enclosed by the
loop, if the loop area is made very small, inductance is
reduced. Additionally, small current loop areas reduce
radiated EMI.
A ceramic input filter capacitor should be placed close to the
VIN pins of the IC. This eliminates as much trace inductance
effects as possible and give the IC a cleaner voltage supply.
A bypass capacitor for the VCC pin also should be placed
close to the pin to reduce effects of trace impedance.
When routing the circuitry around the IC, the analog
small-signal ground and the power ground for switching
currents must be kept separate. They should be connected
together at a point where switching activity is at a
minimum, typically the return terminal of the VCC bypass
capacitor. This helps keep the analog ground quiet.
The ground plane should be kept continuous/unbroken
as far as possible. No trace carrying high switching
current should be placed directly over any ground plane
discontinuity.
PCB layout also affects the thermal performance of the
design. A number of thermal vias that connect to a large
ground plane should be provided under the exposed pad
of the part, for efficient heat dissipation.
For a sample layout that ensures first pass success,
refer to the MAX17504 evaluation kit layout available at
www.maximintegrated.com.
Junction temperature greater than +125°C degrades
operating lifetimes.
www.maximintegrated.com
Maxim Integrated │ 21
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Recommended Component Placement for MAX17504/MAX17504S
VOUT
PLANE
PGND PLANE
L1
LX PLANE
C1
C4
C5
LX PLANE
PGND PLANE
VIN PLANE
MAX17504/
MAX17504S
SGND
C2
R1
R2
MODE
R6
SYNC
C3
C6
R3
R5
R4
SGND PLANE
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Maxim Integrated │ 22
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
VIN
(7.5V TO 60V)
EN/UVLO
VIN
VIN
BST
RT
LX
SYNC
LX
MAX17504
MODE
C2
2.2µF
C1
2.2µF
VIN
L1
10µH
VOUT
5V, 3.5A
C4
22µF
C9
22µF
R3
100kΩ
FB
SGND
CF
C5
0.1µF
LX
VCC
C8
2.2µF
R4
22.1kΩ
RESET
PGND
SS
PGND
PGND
C3
12000pF
fSW = 500kHz
L1 = SLF12575T-100M5R4-H
C4, C9 = 22µF (MURATA GRM32ER71A226K)
Figure 3. MAX17504 Typical Application Circuit for 5V Output, 500kHz Switching Frequency
VIN
(5.5V TO 60V)
EN/UVLO
VIN
VIN
BST
RT
LX
SYNC
MAX17504
MODE
C2
2.2µF
LX
LX
VCC
C8
2.2µF
C5
0.1µF
L1
6.8µH
VOUT
3.3V, 3.5A
C4
22µF
C9
22µF
R3
82.5kΩ
FB
SGND
CF
C1
2.2µF
VIN
R4
30.9kΩ
RESET
SS
PGND
PGND
PGND
C3
12000pF
fSW = 500kHz
L1 = MSS1048-682NL
C4, C9 = 22µF (MURATA GRM32ER71A226K)
Figure 4. MAX17504 Typical Application Circuit for 3.3V Output, 500kHz Switching Frequency
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Maxim Integrated │ 23
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
VIN
C1
2.2µF
R5
EN/UVLO
RT
VIN
VIN
VIN
BST
19.1KΩ
SYNC
C5
0.1µF
L1
4.7µH
LX
C4
22µF
LX
MAX17504S
MODE
VOUT
5V,3.5A
LX
C2
2.2µF
R3
115KΩ
FB
VCC
SGND
R4
24.9KΩ
RESET
CF
SS
PGND
PGND
PGND
C3
12nF
fSW = 1MHz
L1 = 4.7µH (XAL6060, 6mm x 6mm)
C4 = 22µF (MURATA GRM32ER71A226K)
Figure 5. MAX17504S Typical Operating Circuit for 5V Output, 1MHz Switching Frequency
VIN
C1
2.2µF
R5
EN/UVLO
RT
VIN
VIN
VIN
BST
19.1KΩ
SYNC
C5
0.1µF
L1
3.3µH
LX
MODE
C4
47µF
LX
MAX17504S
LX
C2
2.2µF
VOUT
3.3V,3.5A
R3
76.8KΩ
FB
VCC
SGND
R4
28.7KΩ
RESET
CF
SS
PGND
PGND
PGND
C3
12nF
fSW = 1MHz
L1 = 3.3µH (XAL6060, 6mm x 6mm)
C4 = 47µF (MURATA GRM32ER71A476KE15)
Figure 6. MAX17504S Typical Operating Circuit for 3.3V Output, 1MHz Switching Frequency
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Maxim Integrated │ 24
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Ordering Information
PART
PIN-PACKAGE
MAX17504ATP+
20 TQFN-EP* 5mm x 5mm
MAX17504SATP+
20 TQFN-EP* 5mm x 5mm
Note: All devices operate over the temperature range of -40ºC
to +125ºC, unless otherwise noted.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Chip Information
PROCESS: BiCMOS
www.maximintegrated.com
Maxim Integrated │ 25
MAX17504
4.5V–60V, 3.5A, High-Efficiency, Synchronous
Step-Down DC-DC Converter
with Internal Compensation
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
11/13
Initial release
1
2/14
Updated TOC32, TOC33, and Typical Application Circuit figures
2
10/16
Added MAX17504S to data sheet, updated junction temperature, and added TOCs
1-17
5/17
Removed 17504S from data sheet, corrected part numbers in General Description,
Benefits and Features, Detailed Description, Operating Input Voltage Range sections,
updated TOCs 1a, 5, 5a, 6, 7a, 12, 12a, 13, 13a, 14a, 15a, 16a, 17a, 18a, 19a, 20a,
21a, 22, 22a, 23, 23a, 24a, 25a, 26a, 27a, 30a, 32a, Figures 3, 4, 5, and 6, removed
Recommended Component Placement for MAX17504/MAX17504S
1–26
3
—
9, 16, 17
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim
reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2017 Maxim Integrated Products, Inc. │ 26
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