null  User manual
EVALUATION KIT AVAILABLE
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
General Description
The MAX17552/MAX17552A high-efficiency, high-voltage,
synchronous step-down DC-DC converters with integrated
MOSFETs operate over a 4V to 60V input voltage range.
The converters can deliver output current up to 100mA at
output voltages of 0.8V to 0.9 x VIN. The output voltage
is accurate to within ±1.75% over the -40°C to +125°C
temperature range.
The devices employ a peak-current-mode control
architecture with a MODE pin that can be used to operate
the device in pulse-width modulation (PWM) or pulsefrequency modulation (PFM) control schemes. PWM
operation provides constant frequency operation at all
loads and is useful in applications sensitive to variable
switching frequency. PFM operation disables negative
inductor current and additionally skips pulses at light
loads for high efficiency. The converters consume only
22µA of no-load supply current in PFM mode. The lowresistance, on-chip MOSFETs ensure high efficiency at
full load and simplify PCB layout.
The devices offer programmable switching frequency to
optimize solution size and efficiency. Programmable softstart allows the user to reduce the inrush currents. During
overload, the MAX17552 implements a hysteretic cycleby-cycle peak-current-limit protection scheme, while the
MAX17552A implements a HICCUP-type overload protection scheme to protect the inductor and the internal FETs.
An EN/UVLO pin allows the user to turn on/off the device
at the desired input-voltage level. An open-drain RESET
pin allows output-voltage monitoring. The devices operate
over the -40°C to +125°C industrial temperature range
and is available in a compact 10-pin (3mm x 2mm) TDFN
and 10-pin (3mm x 3mm) μMAX® packages. Simulation
models are available.
Applications
●
●
●
●
●
●
Industrial Sensors and Process Control
4mA–20mA Current-Loop Powered Sensors
High-Voltage LDO Replacement
Battery-Powered Equipment
HVAC and Building Control
General-Purpose Point of Load
µMAX is a registered trademark of Maxim Integrated Products, Inc.
19-6903; Rev 3; 6/15
Benefits and Features
● Eliminates External Components and Reduces Total Cost
• No Schottky—Synchronous Operation for High
Efficiency and Reduced Cost
• Internal Compensation
•Fixed Internal 5.1ms or Programmable Soft-Start
• All-Ceramic Capacitors, Ultra-Compact Layout
● Reduces Number of DC-DC Regulators to Stock
• Wide 4V to 60V Input Voltage Range
• Adjustable 0.8V to 0.9 x VIN Output Voltages
• Delivers Up to 100mA Load Current
• 100kHz to 2.2MHz Adjustable Switching Frequency
Range with External Synchronization
• Configurable Between PFM and Forced-PWM
Modes
● Reduces Power Dissipation
• 22µA No Load Supply Current
• Peak Efficiency > 90%
• PFM Feature for High Light-Load Efficiency
• 1.2μA (typ) Shutdown Current
● Operates Reliably in Adverse Industrial Environments
• Peak Current-Limit Protection
• Built-In Output-Voltage Monitoring with Open-Drain
RESET Pin
• Programmable EN/UVLO Threshold
• Monotonic Startup into Prebiased Output
• Overtemperature Protection
• -40°C to +125°C Industrial/Automotive Temperature
Range
Ordering Information appears at end of data sheet.
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Application Circuit—High-Efficiency 5V, 100mA Regulator
VIN
6V TO 60V
IN MAX17552/ LX
L1
220µH
MAX17552A
CIN
1µF
EN/UVLO
GND
SS
VOUT
MODE
COUT
10µF
R4
22.1Ω
C1
0.22µF
FB
RT/SYNC
R3
191kΩ
VOUT
5V, 100mA
R1
261kΩ
R2
49.9kΩ
RESET
SWITCHING FREQUENCY = 220kHz
L1 COILCRAFT LPS5030-224M
COUT MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
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Maxim Integrated │ 2
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Absolute Maximum Ratings
IN, EN/UVLO, VOUT, RESET to GND...................-0.3V to +70V
LX to GND........................................................ -0.3V to IN +0.3V
RT/SYNC, SS, FB, MODE to GND..........................-0.3V to +6V
LX Total RMS Current.........................................................±1.6A
Output Short-Circuit Duration.....................................Continuous
Operating Temperature Range.......................... -40°C to +125°C
Junction Temperature.......................................................+150°C
Storage Temperature Range............................. -65°C to +150°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 Thermal Characteristics (Note 1)
TDFN
Continuous Power Dissipation (TA = +70°C)
(derate 14.9mW/°C above +70°C) ...................... 1188.7mW
Junction-to-Ambient Thermal Resistance (θJA)........67.3°C/W
Junction-to-Case Thermal Resistance (θJC).............18.2°C/W
μMAX
Continuous Power Dissipation (TA = +70°C)
(derate 8.8mW/°C above +70°C)...........................707.3mW
Junction-to-Ambient Thermal Resistance (θJA)......113.1°C/W
Junction-to-Case Thermal Resistance (θJC)................42°C/W
Note 1: 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.
Electrical Characteristics
(VIN = 24V, VGND = 0V, VVOUT = 3.3V, VFB = 0.85V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, LX = SS = MODE = RESET = unconnected;
TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless
otherwise noted) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
60
V
INPUT SUPPLY (IN)
Input Voltage Range
Input Shutdown Current
Input Supply Current
VIN
4
IIN-SH
VEN/UVLO = 0V, TA = +25°C
IQ-PFM
VMODE = unconnected (Note 2)
IQ-PWM
Normal switching mode, VIN = 24V
0.67
1.2
2.25
18
32
245
525
760
2.96
3.05
3.12
µA
EXTERNAL BIAS (VOUT)
VOUT Switchover Threshold
V
ENABLE/UVLO (EN/UVLO)
EN/UVLO Threshold
VENR
VEN/UVLO rising
1.2
1.25
1.3
VENF
VEN/UVLO falling
1.1
1.15
1.2
V
+100
nA
VEN-TRUESD
EN/UVLO Leakage Current
IEN
VEN/UVLO falling, true shutdown
VEN/UVLO = 1.3V, TA = +25°C
0.7
-100
POWER MOSFETs
High-Side pMOS On-Resistance
RDS-ONH
ILX = 0.1A (sourcing)
1.5
2.7
5.1
Ω
Low-Side nMOS On-Resistance
RDS-ONL
ILX = 0.1A (sinking)
0.8
1.4
2.6
Ω
VEN = 0V, TA = +25°C,
VLX = (VGND + 1V) to (VIN - 1V)
-1
+1
µA
LX Leakage Current
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ILX-LKG
Maxim Integrated │ 3
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Electrical Characteristics (continued)
(VIN = 24V, VGND = 0V, VVOUT = 3.3V, VFB = 0.85V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, LX = SS = MODE = RESET = unconnected;
TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless
otherwise noted) (Note 3)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4.4
5.1
5.8
ms
4.7
5
5.3
µA
MODE = GND
0.786
0.8
0.814
MODE = unconnected
0.786
0.812
0.826
VFB = 1V, TA = 25°C
-100
SOFT-START (SS)
Soft-Start Time
tSS
SS Charging Current
ISS
SS = unconnected
FEEDBACK (FB)
FB Regulation Voltage
FB Input Leakage Current
VFB-REG
IFB
V
+100
nA
210
235
mA
105
130
CURRENT LIMIT
Peak Current-Limit Threshold
IPEAK-LIMIT
Negative Current-Limit Threshold
ISINK-LIMIT
PFM Current Level
IPFM
185
VMODE = GND
79
VMODE = unconnected
VMODE = unconnected
0.01
50
72
90
RRT = 422kΩ
90
100
111
RRT = 191kΩ
205
220
235
RRT = 130kΩ
295
319
340
RRT = 69.8kΩ
540
592
638
mA
mA
OSCILLATOR (RT/SYNC)
Switching Frequency
fSW
Switching Frequency Adjustable
Range
RRT = 45.3kΩ
813
900
973
RRT = 19.1kΩ
1.86
2.08
2.3
MHz
See the Switching Frequency (RT/
SYNC) section for details
100
2200
kHz
1.1 x fSW
2200
kHz
SYNC Input Frequency
SYNC Pulse Minimum Off-Time
SYNC Rising Threshold
Hysteresis
kHz
40
ns
VSYNC-H
1
1.22
1.44
VSYNC-HYS
0.115
0.18
0.265
Number of SYNC Pulses to
Enable Synchronization
1
V
Cycles
TIMING
Minimum On-Time
Maximum Duty Cycle
Hiccup Timeout
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tON-MIN
DMAX
46
82
128
fSW ≤ 600kHz,
VFB = 0.98 x VFB-REG
90
94
98
fSW > 600kHz,
VFB = 0.98 x VFB-REG
87
92
MAX17552A
ns
%
51
ms
Maxim Integrated │ 4
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Electrical Characteristics (continued)
(VIN = 24V, VGND = 0V, VVOUT = 3.3V, VFB = 0.85V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, LX = SS = MODE = RESET = unconnected;
TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C. All voltages are referenced to GND, unless
otherwise noted) (Note 3)
RESET
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
FB Threshold for RESET Rising
VFB-OKR
VFB rising
93
95
97
%
FB Threshold for RESET Falling
VFB-OKF
VFB falling
90
92
94
%
RESET Delay after FB Reaches
95% Regulation
RESET Output Level Low
IRESET = 1mA
RESET Output Leakage Current
VFB = 1.01 x VFB-REG, TA = +25°C
2.1
ms
0.23
V
1
µA
1.44
V
MODE
MODE PFM Threshold
VMODE-PFM
MODE Hysteresis
VMODE-HYS
MODE Internal Pullup Resistor
1
1.22
0.19
VMODE = unconnected
(MAX17552)
VMODE = unconnected
(MAX17552A)
V
235
123
kΩ
VMODE = GND
1390
Temperature rising
160
°C
20
°C
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
Note 2: Actual IQ-PFM in the application circuit is higher due to additional current in the output voltage feedback resistor divider. For
example, IQ-PFM (MODE = unconnected) = 26µA for Figure 6, 22µA for Figure 7, and 78µA for Figure 11.
Note 3: Limits are 100% tested at TA = +25°C. Limits over the operating temperature range and relevant supply voltage range are
guaranteed by design and characterization.
www.maximintegrated.com
Maxim Integrated │ 5
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Operating Characteristics
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(MAX17552)
100
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
toc2
toc1
VIN = 12V
VIN = 24V
VIN = 36V
50
40
30
FIGURE 6 APPLICATION
CIRCUIT, PFM MODE
VOUT = 5V
fSW = 220kHz (RRT = 191k)
20
10
1
10
60
VIN = 36V
VIN = 48V
VIN = 24V
50
40
10
0
1
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
VIN = 48V
VIN = 60V
30
FIGURE 7 APPLICATION
CIRCUIT, PFM MODE
VOUT = 3.3V
FSW = 220kHz(RRT = 191k)
20
10
1
10
VIN = 60V
50
VIN = 36V
40
VIN = 12V
toc7
60
VIN = 36V
50
VIN = 48V
40
VIN = 60V
30
20
FIGURE 6 APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 220kHz (RRT = 191k)
10
0
20
40
60
LOAD CURRENT (mA)
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60
50
40
VIN = 12V
10
FIGURE 7 APPLICATION CIRCUIT,
PFM MODE, VOUT = 3.3V
FSW = 600kHz (RRT = 69.8k)
20
10
0
100
1
10
80
100
90
80
80
VIN = 12V
VIN = 24V
50
VIN = 36V
40
VIN = 48V
30
VIN = 60V
20
10
0
0
20
70
VIN = 24V
60
toc9
VIN = 12V
VIN = 36V
50
40
VIN = 48V
30
FIGURE 6 APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 220kHz (R RT = 191k)
40
EFFICIENCY VS. LOAD CURRENT
(MAX17552)
100
90
70
100
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
toc8
60
VIN = 36V
VIN = 24V
30
1
100
VIN = 12V
toc6
70
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 24V
70
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
100
FIGURE 6 APPLICATION CIRCUIT,
PFM MODE, VOUT = 5V
FSW = 600kHz (RRT = 69.8k)
10
90
80
VIN = 48V
VIN = 24V
30
0
100
80
60
20
100
EFFICIENCY vs. LOAD CURRENT
(MAX17552)
100
10
90
LOAD CURRENT (mA)
EFFICIENCY (%)
toc5
EFFICIENCY (%)
VIN = 12V
1
LOAD CURRENT (mA)
EFFICIENCY (%)
EFFICIENCY (%)
EFFICIENCY (%)
VIN = 24V
40
0
0
70
50
VIN = 36V
FIGURE 7 APPLICATION
CIRCUIT, PFM MODE
VOUT = 3.3V
fSW = 220kHz (RRT = 191k)
10
80
VIN = 36V
VIN = 24V
40
100
EFFICIENCY vs LOAD CURRENT
(MAX17552A)
toc4
80
60
VIN = 12V
50
20
90
70
60
LOAD CURRENT (mA)
90
0
10
70
30
FIGURE 6 APPLICATION
CIRCUIT, PFM MODE
VOUT = 5V
fSW = 220kHz (RRT = 191k)
20
LOAD CURRENT (mA)
100
VIN = 60V
VIN = 12V
30
100
EFFICIENCY (%)
60
EFFICIENCY (%)
EFFICIENCY (%)
80
70
70
toc3
90
80
80
0
100
90
90
EFFICIENCY vs. LOAD CURRENT
(MAX17552)
60
LOAD CURRENT (mA)
80
100
VIN = 60V FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, VOUT = 3 3V
.
FSW = 220kHz (RRT = 191k)
20
10
0
0
20
40
60
80
100
LOAD CURRENT (mA)
Maxim Integrated │ 6
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
90
70
VIN = 12V
60
VIN = 24V
50
VIN = 36V
40
VIN = 48V
30
20
0
20
90
80
80
70
VIN = 12V
60
VIN = 24V
50
VIN = 36V
40
VIN = 48V
40
60
80
10
0
100
0
20
40
EFFICIENCY VS. LOAD CURRENT
(MAX17552)
80
70
70
EFFICIENCY (%)
VIN = 12V
VIN = 36V
40
20
0
20
40
60
60
50
VIN = 36V
80
0
100
0
20
40
VIN = 12V,24V
3.32
FIGURE 7 APPLICATION CIRCUIT,
PFM MODE
20
40
60
LOAD CURRENT (mA)
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80
5.04
100
VIN = 12V
4.941
VIN = 36V V = 48V
IN
VIN = 24V
VIN = 60V
4.939
4.937
100
VIN = 48V
VIN = 60V
VIN = 12V
4.98
VIN = 24V
0
20
40
60
80
100
LOAD CURRENT (mA)
FIGURE6 APPLICATION
CIRCUIT, PWM MODE
4.943
80
VIN = 36V
5.01
4.92
100
OUTPUT VOLTAGE vs. LOAD CURRENT
3.330
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE
3.328
4.945
VIN = 60V
0
80
OUTPUT VOLTAGE vs. LOAD CURRENT
4.947
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.36
VIN = 48V
60
60
toc18
VIN = 36V
40
FIGURE 6 APPLICATION
CIRCUIT, PFM MODE
4.95
toc17
3.38
3.28
VIN = 24V
VIN = 12V
LOAD CURRENT (mA)
toc16
3.40
3.30
20
OUTPUT VOLTAGE vs. LOAD CURRENT
5.10
toc14
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, VOUT = 3.3V
FSW = 600kHz (RRT = 69.8k)
10
OUTPUT VOLTAGE vs. LOAD CURRENT
3.34
0
LOAD CURRENT (mA)
40
LOAD CURRENT (mA)
3.42
0
100
5.07
20
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, VOUT = 3.3V
FSW = 600kHz (RRT = 69.8k)
10
VIN = 48V
VIN = 60V
FIGURE 6 APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 600kHz (RRT = 69.8k)
10
30
30
0
80
VIN = 12V
VIN = 36V
40
20
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
80
50
60
EFFICIENCY VS. LOAD CURRENT
(MAX17552A)
100
90
VIN = 24V
VIN = 24V
50
toc12
toc15
toc13
90
60
60
LOAD CURRENT (mA)
LOAD CURRENT (mA)
100
70
30
VIN = 60V FIGURE 6 APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 600kHz (RRT = 69.8k)
20
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
100
90
30
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, VOUT = 3.3V
FSW = 220kHz (RRT = 191k)
VIN = 60V
10
0
EFFICIENCY (%)
EFFICIENCY (%)
80
toc11
OUTPUT VOLTAGE (V)
100
EFFICIENCY vs. LOAD CURRENT
(MAX17552)
100
toc10
EFFICIENCY (%)
EFFICIENCY VS. LOAD CURRENT
(MAX17552A)
3.326
3.324
VIN = 12V
3.322
VIN = 24V
VIN = 36V VIN = 48V
VIN = 60V
3.320
3.318
0
20
40
60
LOAD CURRENT (mA)
80
100
3.316
0
20
40
60
80
100
LOAD CURRENT (mA)
Maxim Integrated │ 7
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
OUTPUT VOLTAGE vs. LOAD CURRENT
VVININ=24V
= 24V
VVININ=36V
= 36V
4.94
4.90
VIN = 48V
VIN = 60V
0
20
40
4.958
3.36
VIN = 12V
3.32
VIN = 24V
3.24
60
80
100
FIGURE 9 APPLICATION CIRCUIT,
PFM MODE
0
20
40
LOAD CURRENT (mA)
60
80
3.323
60
80
toc23
0.79
0.78
100
toc25
-40
-20
0
5
15
25
35
45
INPUT VOLTAGE (V)
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0
20
55
40
60
80
100
NO LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE
toc24
100
40
60
80
80
60
40
20
0
100 120
1.4
1.1
0.8
-40
-20
0
20
40
60
TEMPERATURE (°C)
15
25
35
45
55
80
100
120
SWITCH CURRENT LIMIT
vs. INPUT VOLTAGE
250
toc26
1.7
0.5
5
INPUT VOLTAGE (V)
SWITCH CURRENT LIMIT (mA)
SHUTDOWN CURRENT (µA)
SHUTDOWN CURRENT (µA)
-0.5
-2.0
20
SHUTDOWN CURRENT
vs. TEMPERATURE
2.0
4.0
1.0
VIN = 60V
4.951
TEMPERATURE (°C)
2.5
VIN = 48V
LOAD CURRENT (mA)
0.80
LOAD CURRENT (mA)
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
VIN = 36V
4.952
4.949
NO LOAD SUPPLY CURRENT (µA)
VIN = 12V VIN = 24V
VIN = 36V
40
4.953
PFM MODE
FEEDBACK VOLTAGE (V)
OUTPUT VOLTAGE (V)
3.325
20
VIN = 12V
4.954
4.950
100
0.81
0
4.955
toc22
FIGURE 9 APPLICATION CIRCUIT,
PWM MODE
FEEDBACK VOLTAGE
VS. TEMPERATURE
0.82
3.327
3.321
4.956
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
3.329
VIN = 36V
3.28
3.20
VIN = 24V
4.957
3.40
OUTPUT VOLTAGE (V)
4.98
FIGURE 8 APPLICATION CIRCUIT,
PWM MODE
4.959
3.44
OUTPUT VOLTAGE (V)
VVININ=12V
= 12V
OUTPUT VOLTAGE vs. LOAD CURRENT
4.960
toc20
5.06
5.02
3.48
toc19
5.10
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE vs. LOAD CURRENT
FIGURE
8 APPLICATION
FIGURE8
APPLICATION
CIRCUIT,
PFMPFM
MODE
CIRCUIT,
MODE
toc21
5.14
200
toc27
SWITCH PEAK
CURRENT LIMIT
150
100
SWITCH NEGATIVE
CURRENT LIMIT
50
0
5
15
25
35
45
55
INPUT VOLTAGE (V)
Maxim Integrated │ 8
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
200
SWITCH PEAK
CURRENT LIMIT
150
100
SWITCH NEGATIVE
CURRENT LIMIT
50
0
EN/UVLO THRESHOLD VOLTAGE
vs. TEMPERATURE
1.30
toc29
RISING
1.26
1.22
1.18
1.14
SWITCHING FREQUENCY
vs. TEMPERATURE
1000
SWITCHING FREQUENCY (KHz)
SWITCH CURRENT LIMIT (mA)
250
toc28
EN/UVLO THRESHOLD VOLTAGE (V)
SWITCH CURRENT LIMIT
vs. TEMPERATURE
800
RT = 69.8kΩ
600
400
RT = 191kΩ
200
RT = 422kΩ
FALLING
1.10
-40 -20
0
20
40
60
80
100 120
96
-20
0
20
40
60
80
100
120
0
LOAD TRANSIENT RESPONSE,
PFM MODE (LOAD CURRENT STEPPED
FROM 5mA to 50mA)
toc32
toc31
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET THRESHOLD
vs. TEMPERATURE
-40
toc30
RT = 45.3kΩ
LOAD TRANSIENT RESPONSE
PFM MODE (LOAD CURRENT STEPPED
FROM 5mA to 50mA)
toc33
RISING
RESET THRESHOLD (%)
95
VOUT
(AC)
94
FIGURE6
APPLICATION
FIGURE 6 CIRCUIT
APPLICATIONVOUT
CIRCUIT
=5V
VOUT = 5V
93
92
FALLING
91
90
-40
-20
0
20
40
60
IOUT
80
100
120
VOUT
(AC)
LOAD TRANSIENT RESPONSE
PFM OR PWM MODE (LOAD CURRENT
STEPPED FROM 50mA TO 100mA) toc34
50mA/div
IOUT
LOAD TRANSIENT RESPONSE
PWM MODE (LOAD CURRENT STEPPED
FROM NO-LOAD TO 50mA) toc36
toc35
VOUT
(AC)
50mA/div
200µs/div
LOAD TRANSIENT RESPONSE
PFM OR PWM MODE (LOAD CURRENT
STEPPED FROM 50mA TO 100mA)
100mV/div
100mV/div
FIGURE7
FIGURE 7APPLICATION
APPLICATION CIRCUIT
VOUT = 3.3V VOUT=3.3V
200µs/div
TEMPERATURE (°C)
VOUT
(AC)
100mV/div
100mV/div
VOUT
(AC)
100mV/div
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
50mA/div
IOUT
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
100µs/div
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IOUT
FIGURE 7
APPLICATION CIRCUIT
VOUT = 3.3V
100µs/div
50mA/div
IOUT
50mA/div
100µs/div
Maxim Integrated │ 9
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
LOAD TRANSIENT RESPONSE
PWM MODE (LOAD CURRENT STEPPED
FROM NO-LOAD TO 50mA) toc37
SWITCHING WAVEFORMS
(PFM MODE)
toc38
FULL LOAD-SWITCHING WAVEFORMS
(PWM OR PFM MODE) toc39
FIGURE 6 APPLICATION CIRCUIT
VOUT = 5V,LOAD = 20mA
100mV/
div
VOUT
(AC)
FIGURE 7
APPLICATION CIRCUIT
VOUT = 3.3V
50mA/div
IOUT
VOUT
(AC)
100mV/div
LX
10V/div
ILX
100mA/div
20mV/div
VOUT
(AC)
LX
10V/div
ILX
100mA/div
4µs/div
10µs/div
100µs/div
NO LOAD SWITCHING WAVEFORMS
(PWM MODE)
toc40
VOUT
(AC)
FIGURE 6 APPLICATION CIRCUIT
VOUT = 5V, LOAD = 100mA
SOFT START
FIGURE 6 APPLICATION CIRCUIT
VOUT = 5V
20mV/div
SOFT START
toc41
5V/div
5V/div
VEN/UVLO
2V/div
toc42
VEN/UVLO
1V/div
VOUT
LX
10V/div
IOUT
100mA/div
ILX
VRESET
toc43
SOFT START WITH 3V PREBIAS
1V/div
2ms/div
www.maximintegrated.com
VLX
FIGURE 6
APPLICATION CIRCUIT
NO LOAD
PWM MODE
50mA/div
5V/div
EXTERNAL SYNCHRONIZATION WITH
300kHz CLOCK FREQUENCY
toc44
5V/div
VOUT
5V/div
VRESET
2V/div
toc45
2V/div
VRESET
VRESET
50mA/div
1ms/div
VEN/UVLO
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
IOUT
FIGURE 7
APPLICATION
CIRCUIT
VOUT = 3.3V
IOUT
5V/div
5V/div
VEN/UVLO
VOUT
VOUT
1ms/div
4µs/div
SHUTDOWN WITH ENABLE
50mA/div
FIGURE 6
APPLICATION
CIRCUIT
VOUT = 5V
1ms/div
VRT/SYNC
10V/div
FIGURE 6
APPLICATION
CIRCUIT
100mA LOAD
PWM MODE
2V/div
4µs/div
Maxim Integrated │ 10
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
OVERLOAD PROTECTION
(MAX17552)
VOUT
OVERLOAD PROTECTION
(MAX17552A)
toc46
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
BODE PLOT
toc47
toc48
50
5V/div
108
30
20
PHASE
10
-10
I LX
BODE PLOT
50
toc49
144
30
108
PHASE
10
GAIN
-36
-72
1k
10k
100k
-180
180
40
20
-40
-50
20ms/div
36
-108
FIGURE 6 APPLICATION CIRCUIT
-144
VOUT = 5V
-30
100mA/div
1ms/div
FCR = 8.5KHz,
PHASE MARGIN = 64°
-20
100mA/div
72
0
0
ILX
180
144
40
72
36
0
0
FCR = 10.5KHz,
PHASE MARGIN = 61°
-10
-20
GAIN
-36
-72
-108
FIGURE 7 APPLICATION CIRCUIT
-144
VOUT = 3.3V
-180
-30
-40
-50
1k
10k
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100k
Maxim Integrated │ 11
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Pin Configuration
TOP VIEW
LX
10
GND MODE RESET VOUT
9
8
7
6
MAX17552/
MAX17552A
+
1
IN
2
3
4
5
EN/ RT/ SS
UVLO SYNC
FB
IN
1
EN/UVLO
2
RT/SYNC
3
SS
4
FB
5
+
MAX17552/
MAX17552A
10
LX
9
GND
8
MODE
7
RESET
6
VOUT
µMAX
3mm x 3mm
TDFN
3mm x 2mm
Pin Description
PIN
NAME
1
IN
Switching Regulator Input. Connect a X7R 1µF ceramic capacitor from IN to GND for bypassing.
2
EN/UVLO
Active-High, Enable/Undervoltage-Detection Input. Pull EN/UVLO to GND to disable the regulator
output. Connect EN/UVLO to IN for always-on operation. Connect a resistor-divider between IN,
EN/UVLO, and GND to program the input voltage at which the device is enabled and turns on.
3
RT/SYNC
Oscillator Timing Resistor Input. Connect a resistor from RT/SYNC to GND to program the switching
frequency from 100kHz to 2.2MHz. See the Switching Frequency (RT/SYNC) section for details. An
external pulse can be applied to RT/SYNC through a coupling capacitor to synchronize the internal clock
to the external pulse frequency. See the External Synchronization section for details.
4
SS
Soft-Start Capacitor Input. Connect a capacitor from SS to GND to set the soft-start time. Leave SS
unconnected for default 5.1ms internal soft-start.
5
FB
Output Feedback Connection. Connect FB to a resistor-divider between VOUT and GND to set the
output voltage. See the Adjusting the Output Voltage section for details.
6
VOUT
External Bias Input for Internal Control Circuitry. Decouple to GND with a 0.22μF capacitor and connect to
output capacitor positive terminal with a 22.1Ω resistor for applications with an output voltage from 3.3V to
5V. Connect to GND for output voltages < 3.3V and > 5V. See the External Bias section for details.
7
RESET
Open-Drain Reset Output. Pull up RESET to an external power supply with an external resistor. RESET
pulls low if FB voltage drops below 92% of its set value. RESET goes high impedance 2ms after FB
voltage rises above 95% of its set value.
8
MODE
PFM/PWM Mode-Selection Input. Connect MODE to GND to enable the fixed-frequency PWM
operation. Leave MODE unconnected for light-load PFM operation.
9
GND
10
LX
Inductor Connection. Connect LX to the switching side of the inductor. LX is high impedance when the
device is in shutdown.
—
EP
Exposed Pad (TDFN Only). Connect to the GND pin to the IC.
www.maximintegrated.com
FUNCTION
Ground. Connect GND to the power ground plane. Connect all the circuit ground connections together at
a single point. See the PCB Layout Guidelines section.
Maxim Integrated │ 12
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Block Diagram
IN
INTERNAL
LDO
REGULATOR
VOUT
POK
VCC_INT
PEAK-LIMIT
EN/UVLO
CURRENTSENSE
LOGIC
CHIPEN
1.25V
PFM
THERMAL
SHUTDOWN
CLK
RT/SYNC
PFM/PWM
CONTROL
LOGIC
OSCILLATOR
SLOPE
VCC_INT
SLOPE
SS
CS
INTERNAL OR
EXTERNAL
SOFT-START
CONTROL
DH
LX
LOW-SIDE
DRIVER
MODE SELECT
1.22V
FB
CURRENTSENSE
AMPLIFIER
HIGH-SIDE
DRIVER
DL
MODE
CS
SINK-LIMIT
CURRENT
SENSE
AMPLIFIER
PWM
ERROR
AMPLIFIER
NEGATIVE
CURRENT
REF
GND
RESET
0.76V
FB
CLK
2ms
DELAY
MAX17552/MAX17552A
www.maximintegrated.com
Maxim Integrated │ 13
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Detailed Description
The MAX17552/MAX17552A high-efficiency, high-voltage,
synchronous step-down DC-DC converters with integrated
MOSFETs operate over a 4V to 60V input voltage range.
The converter can deliver output current up to 100mA at
output voltages of 0.8V to 0.9 x VIN. The output voltage
is accurate to within ±1.75% over -40°C to +125°C. The
converter consumes only 22µA of supply current in PFM
mode while regulating the output voltage at no load.
The devices use an internally compensated, peakcurrent-mode control architecture (see the Block
Diagram). On the rising edge of the internal clock, the
high-side pMOSFET turns on. An internal error amplifier
compares the feedback voltage to a fixed internal reference
voltage and generates an error voltage. The error voltage
is compared to a sum of the current-sense voltage and
a slope-compensation voltage by a PWM comparator to
set the “on-time.” During the on-time of the pMOSFET,
the inductor current ramps up. For the remainder of the
switching period (off-time), the pMOSFET is kept off and
the low-side nMOSFET turns on. During the off-time,
the inductor releases the stored energy as the inductor
current ramps down, providing current to the output.
Under overload conditions, cycle-by-cycle current-limit
feature limits inductor peak current by turning off the highside pMOSFET and turning on the low-side nMOSFET.
Mode Selection (MODE)
The devices feature a MODE pin for selecting either
forced-PWM or PFM mode of operation. If the MODE pin
is left unconnected, the devices operate in PFM mode
at light loads. If the MODE pin is grounded, the devices
operate in a constant-frequency forced-PWM mode at all
loads. Mode of operation can be changed on-the-fly during
normal operation of the device.
In PWM mode, the inductor current is allowed to go
negative. PWM operation is useful in frequency-sensitive
applications and provides fixed switching frequency at
all loads. However, the PWM mode of operation gives
lower efficiency at light loads compared to PFM mode of
operation.
PFM mode 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 72mA (typ) (IPFM) every clock cycle until the output
rises to 102% (typ) of the nominal voltage. Once the
output reaches 102% (typ) of the nominal voltage, both
high-side and low-side FETs are turned off and the device
www.maximintegrated.com
enters hibernate operation until the load discharges the
output to 101% (typ) 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% (typ) of the nominal voltage, the devices come
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% (typ) of the
nominal output voltage. The devices naturally exit PFM
mode when the load current increases to a magnitude of
approximately:
IPFM - (ΔI/2)
where ΔI is the peak-peak ripple current in the output
inductor. The part enters PFM mode again if the load
current reduces to approximately (ΔI/2). See the Inductor
Selection section for details. The advantage of the PFM
mode is higher efficiency at light loads because of lower
current drawn from the supply.
Enable Input (EN/UVLO) and Soft-Start (SS)
When EN/UVLO voltage increases above 1.25V (typ), the
devices initiate a soft-start sequence and the duration of
the soft-start depends on the status of the SS pin voltage
at the time of power-up. If the SS pin is not connected,
the devices use a fixed 5ms internal soft-start to ramp
up the internal error-amplifier reference. If a capacitor is
connected from SS to GND, a 5μA current source charges
the capacitor and ramps up the SS pin voltage. The SS
pin voltage is used as reference for the internal error
amplifier. Such a reference ramp up allows the output
voltage to increase monotonically from zero to the final
set value independent of the load current.
EN/UVLO can be used as an input voltage UVLOadjustment input. An external voltage-divider between
IN and EN/UVLO to GND adjusts the input voltage at
which the device turns on or turns off. See the Setting
the Input Undervoltage-Lockout Level section for details.
If input UVLO programming is not desired, connect EN/
UVLO to IN (see the Electrical Characteristics table for
EN/UVLO rising and falling-threshold voltages). Driving
EN/UVLO low disables both power MOSFETs, as well as
other internal circuitry, and reduces IN quiescent current
to below 1.2μA. The SS capacitor is discharged with an
internal pulldown resistor when EN/UVLO is low. If the
EN/UVLO pin is driven from an external signal source,
a series resistance of minimum 1kW is recommended to
be placed between the signal source output and the EN/
UVLO pin, to reduce voltage ringing on the line.
Maxim Integrated │ 14
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Switching Frequency (RT/SYNC)
Switching frequency of the devices can be programmed
from 100kHz to 2.2MHz by using a resistor connected
from RT/SYNC to GND. The switching frequency (fSW)
is related to the resistor connected at the RT/SYNC pin
(RT) by the following equation, where RT is in kΩ and fSW
is in kHz:
RT =
42000
f SW
The switching frequency in ranges of 130kHz to 160kHz
and 230kHz to 280kHz are not allowed for user programming to ensure proper configuration of the internal
adaptive-loop compensation scheme.
External Synchronization
The RT/SYNC pin can be used to synchronize the
device’s internal oscillator to an external system clock.
The external clock should be coupled to the RT/SYNC
pin through a 47pF capacitor, as shown in Figure 1. The
external clock logic high level should be higher than
3V, logic low level lower than 0.5V and the duty cycle
of the external clock should be in the range of 10% to
70%. External clock synchronization is allowed only in
PWM mode of operation (MODE pin connected to GND).
The RT resistor should be selected to set the switching
frequency 10% lower than the external clock frequency.
The external clock should be applied at least 500μs
after enabling the device, for proper configuration of the
internal loop compensation.
MAX17552/
MAX17552A
47pF
RT/SYNC
CLOCK
SOURCE
RT
VLOGIC-HIGH
VLOGIC-LOW
DUTY
Figure 1. Synchronization to an External Clock
www.maximintegrated.com
External Bias (VOUT)
The devices provide a VOUT pin to power the internal
blocks from a low-voltage supply. When the VOUT pin
voltage exceeds 3.1V, the devices draw switching and
quiescent current from this pin to improve the converter’s
efficiency. In applications with an output voltage setting
from 3.3V to 5V, VOUT should be decoupled to GND
with a ceramic capacitor, and should be connected to the
positive terminal of the output capacitor with a resistor
(R4, C1) as shown in the typical application circuits. In
the absence of R4 and C1, the absolute maximum rating of VOUT (-0.3V) can be exceeded under short-circuit
conditions, due to oscillations between the ceramic output
capacitor and the inductance of the short-circuit path. In
general, parasitic board or wiring inductance should be
minimized and the output voltage waveform under short
circuit operation should be verified to ensure that the
absolute maximum rating of VOUT is not exceeded. For
applications with an output voltage setting less than 3.3V
or greater than 5V, VOUT should be connected to GND.
Reset Output (RESET)
The devices include an open-drain RESET output to
monitor output voltage. RESET should be pulled up with
an external resistor to the desired external power supply.
RESET goes high impedance 2ms after the output rises
above 95% of its nominal set value and pulls low when
the output voltage falls below 92% of the set nominal
output voltage.
Startup Into a Prebiased Output
The devices support monotonic startup into a prebiased
output. When the device starts into a prebiased output,
both the high-side and 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. Such a feature is
useful in applications where digital integrated circuits with
multiple rails are powered.
Operating Input Voltage Range
The maximum operating input voltage is determined
by the minimum controllable on-time, and the minimum
operating input voltage is determined by the maximum
duty cycle and circuit voltage drops. The minimum and
maximum operating input voltages for a given output voltage should be calculated as follows:
Maxim Integrated │ 15
MAX17552/MAX17552A
VINMIN
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
VOUT + (I OUT × (R DCR + 2.6))
+ (I OUT × 2.5)
D MAX
VOUT
VINMAX =
t ONMIN × f SW
where VOUT is the steady-state output voltage, IOUT is
the maximum load current, RDCR is the DC resistance of
the inductor, fSW is the switching frequency (max), DMAX
is the maximum duty cycle (0.9), and tONMIN is the worstcase minimum controllable switch on-time (128ns)
Overcurrent Protection
The MAX17552 implements a hysteretic cycle-by-cycle
peak-current limit protection scheme to protect the inductor
and internal FETs under output short circuit conditions.
When the inductor peak current exceeds 0.21A (typ), high
side switch is turned off and low side switch is turned
on to discharge the inductor current. Subsequent clock
pulses do not turn on the high-side switch until inductor
current discharges to 0.15A (typ). This operation continues until overload/short circuit is removed on the output.
Since the inductor current is bounded between two limits,
inductor current runaway never happens in this scheme.
Additionally, hysteretic negative peak current limit controls
the low-side switch negative current when it exceeds 0.1A
(typ).
The MAX17552A implements a HICCUP-type overload
protection scheme to protect the inductor and internal
FETs under output short-circuit conditions. When the
inductor peak current exceeds 0.21A (typ) 16 consecutive times, the part enters HICCUP mode. In this mode,
the part is initially operated with hysteretic cycle-by-cycle
peak-current limit that continues for a time period equal
to twice the soft-start time. The part is then turned off
for a fixed 51ms hiccup timeout period. This sequence
of hysteretic inductor current waveforms, followed by a
hiccup timeout period, continues until the short/overload
on the output is removed. Since the inductor current is
bound between two limits, inductor current runway never
happens.
Thermal-Overload Protection
Thermal-overload protection limits the total power dissipation in the IC. When the junction temperature exceeds
+160°C, an on-chip thermal sensor shuts down the
device, turns off the internal power MOSFETs, allowing
the device to cool down. The device turns on after the
junction temperature cools by 20°C.
www.maximintegrated.com
Applications Information
Inductor Selection
A low-loss inductor having the lowest possible DC resistance
that fits in the allotted dimensions should be selected.
Calculate the required inductance from the equation:
L=
10000 x VOUT
f SW
where L is inductance in μH, VOUT is output voltage
and fSW is the switching frequency in kHz. Calculate the
peak-peak ripple current (ΔI) in the output inductor from
the equation:


V
1000 × VOUT × 1 − OUT 
V
IN 

∆I =
f SW × L
where L is inductance in μH, VOUT is output voltage, VIN
is input voltage and fSW is the switching frequency in kHz.
The saturation current rating of the inductor must exceed
the maximum current-limit value (IPEAK-LIMIT). The saturation current rating should be the maximum of either
0.235A or the value from the equation:
I=
SAT
0.15 +
VINMAX × t ON−MIN
L
where L is inductance in H, VINMAX is maximum input
voltage and tON-MIN is worst case minimum on time
(128ns).
Once the L value is known, the next step is to select the
right core material. Ferrite and powdered iron are commonly available core materials. Ferrite cores have low
core losses and are preferred for high-efficiency designs.
Powdered iron cores have more core losses and are relatively cheaper than ferrite cores.
Input Capacitor Selection
Small ceramic input capacitors are recommended for the
IC. The input capacitor reduces peak current drawn from
the power source and reduces noise and voltage ripple
on the input caused by the switching circuitry. A minimum
of 1μF, X7R-grade capacitor in a package larger than 0805
is recommended for the input capacitor of the IC to keep the
input-voltage ripple under 2% of the minimum input voltage,
and to meet the maximum ripple-current requirements.
Maxim Integrated │ 16
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Output Capacitor Selection
Small ceramic X7R-grade output capacitors are recommended for the devices. The output capacitor has two
functions. It stores sufficient energy to support the output
voltage under load transient conditions and stabilizes the
device’s internal control loop. Usually the output capacitor
is sized to support a step load of 50% of the maximum
output current in the application, such that the outputvoltage deviation is less than 3%. Calculate the minimum
required output capacitance from the following equations:
Frequency
Range
(kHz)
Minimum Output
Capacitance
(μF)
50
100 to 130
VOUT
25
160 to 230
VOUT
17
VOUT
280 to 2200
It should be noted that dielectric materials used in ceramic
capacitors exhibit capacitance loss due to DC bias levels and
should be appropriately derated to ensure the required
output capacitance is obtained in the application.
Soft-Start Capacitor Selection
The devices offer a 5.1ms internal soft-start when the
SS pin is left unconnected. When adjustable soft-start
time is required, connect a capacitor from SS to GND
to program the soft-start time. The minimum soft-start time
is related to the output capacitance (COUT) and the output
voltage(VOUT) by the following equation.
tSS > 0.05 x COUT x VOUT
where tSS is in milliseconds and COUT is in µF.
Soft-start time (tSS) is related to the capacitor connected at
SS (CSS) by the following equation:
C=
SS 6.25 × t SS
where tSS is in milliseconds and CSS is in nanofarads.
Setting the Input Undervoltage-Lockout Level
The devices offer an adjustable input undervoltagelockout level. Set the voltage at which the device turns on
with a resistive voltage-divider connected from IN to GND
(see Figure 2). Connect the center node of the divider to
EN/UVLO.
Choose R1 to be 3.3MΩ max and then calculate R2 as
follows:
R2 =
R1× 1.25
(VINU - 1.25)
where VINU is the voltage at which the device is required
to turn on.
VOUT
VIN
IN
R1
MAX17552/
MAX17552A
EN/UVLO
MAX17552/
MAX17552A
R1
FB
R2
R2
GND
Figure 2. Adjustable EN/UVLO Network
www.maximintegrated.com
Figure 3. Setting the Output Voltage
Maxim Integrated │ 17
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
the power supply. At a particular operating condition, the
power losses that lead to temperature rise of the device
are estimated as follows:
4.7Ω
IN
CIN
1µF
MAX17552/
MAX17552A
GND
Figure 4. Transient Protection
Adjusting the Output Voltage
The output voltage can be programmed from 0.8V to 0.9V
x VIN. Set the output voltage by connecting a resistordivider from output to FB to GND (see Figure 3). Choose
R2 in the range of 25kΩ to 100kΩ and calculate R1 with
the following equation:
=
R1
V
R2 ×  OUT
 0.8
−

1

Transient Protection
In applications where fast line transients or oscillations
with a slew rate in excess of 15V/µs are expected during power-up or steady-state operation, the MAX17552/
MAX17552A should be protected with a series resistor
that forms a lowpass filter with the input ceramic capacitor
(Figure 4). These transients can occur in conditions such
as hot-plugging from a low-impedance source or due to
inductive load switching and surges on the supply lines.

 1 
2
PLOSS =
POUT ×  - 1  - (I OUT × R DCR )
 η 

P=
OUT VOUT × I OUT
where POUT is the output power, η is the efficiency of
power conversion, and RDCR is the DC resistance of the
output inductor. See the Typical Operating Characteristics
for the power-conversion efficiency or measure the efficiency to determine the total power dissipation.
The junction temperature (TJ) of the device can be
estimated at any ambient temperature (TA) from the
following equation:
TJ= T A + (θ JA × PLOSS )
where θJA is the junction-to-ambient thermal impedance
of the package.
PCB Layout Guidelines
Careful PCB layout (Figure 5) is critical to achieve clean
and stable operation. The switching power stage requires
particular attention. Follow these guidelines for good PCB
layout:
● Place the input ceramic capacitor as close as possible
to VIN and GND pins
● Minimize the area formed by the LX pin and inductor
connection to reduce the radiated EMI
● Ensure that all feedback connections are short and
direct
● Route high-speed switching node (LX) away from the
signal pins
Power Dissipation
For a sample PCB layout that ensures the first-pass
success, refer to the MAX17552/MAX17552A evaluation
kit data sheet.
www.maximintegrated.com
Maxim Integrated │ 18
Ensure that the junction temperature of the devices do not
exceed 125°C under the operating conditions specified for
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
VIN
IN
MAX17552/
MAX17552A
R1
CIN
CSS
VOUT
COUT
GND
EN/UVLO
R2
L1
LX
SS
VOUT
CF
R7
MODE
FB
RT/SYNC
R4
R5
R3
R6
VOUT
RESET
GND PLANE
CIN
VIN PLANE
R3
VOUT PLANE
U1
R1
R2
L1
LX
IN
EN/UVLO
GND
RT/SYNC
MODE
RESET
SS
FB
CSS
COUT
R6
R4
VOUT
R7
R5
GND PLANE
CF
Vias to Bottom-Side Ground Plane
Vias to VOUT
Vias to RESET
Figure 5. Layout Guidelines
www.maximintegrated.com
Maxim Integrated │ 19
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Application Circuits
VIN
6V TO 60V
CIN
1µF
L1
220µH
IN MAX17552/ LX
MAX17552A
EN/UVLO
COUT
10µF
GND
MODE
C1
0.22µF
RT/SYNC
MAX17552/ LX
MAX17552A
EN/UVLO
SS
GND
VOUT
MODE
R1
261kΩ
FB
R3
191kΩ
IN
CIN
1µF
R4
22.1Ω
SS
VOUT
VIN
4V TO 60V
VOUT
5V, 100mA
RT/SYNC
R2
49.9kΩ
L1
150µH
VOUT
3.3V, 100mA
COUT
10µF
R4
22.1Ω
C1
0.22µF
R1
158kΩ
FB
R2
49.9kΩ
R3
191kΩ
RESET
RESET
SWITCHING FREQUENCY = 220kHz
L1 COILCRAFT LPS5030-224M
COUT MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
SWITCHING FREQUENCY = 220kHz
L1 COILCRAFT LPS5030-154M
COUT MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
Figure 7. High-Efficiency 3.3V, 100mA Regulator
Figure 6. High-Efficiency 5V, 100mA Regulator
VIN
6V TO 60V
IN MAX17552/ LX
L1
100µH
MAX17552A
CIN
1µF
EN/UVLO
SS
MODE
R4
22.1Ω
C1
0.22µF
R1
261kΩ
FB
R2
49.9kΩ
RT/SYNC
R3
69.8kΩ
COUT
10µF
GND
VOUT
VOUT
5V, 100mA
RESET
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS3015-104M
COUT MURATA 10µF/X7R/6.3V/0805 (GRM21BR70J106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
Figure 8. Small Footprint 5V, 100mA Regulator
www.maximintegrated.com
Maxim Integrated │ 20
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Typical Application Circuits (continued)
VIN
4V TO 45V
IN MAX17552/ LX
L1
68µH
EN/UVLO
SS
MODE
GND
VOUT
IN MAX17552/ LX
MAX17552A
CIN
1µF
R4
22.1Ω
EN/UVLO
SS
C1
0.22µF
R1
158kΩ
FB
MODE
R2
49.9kΩ
RT/SYNC
R3
69.8kΩ
VIN
4V TO 24V
COUT
10µF
MAX17552A
CIN
1µF
VOUT
3.3V, 100mA
R3
69.8kΩ
Figure 9. Small Footprint 3.3V, 100mA Regulator
VOUT
R1
127kΩ
FB
R2
100kΩ
RESET
Figure 10. Small Footprint 1.8V, 100mA Regulator
IN MAX17552/ LX
MAX17552A
CIN
1µF
COUT
10µF
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS3015-333M
COUT MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS3015-683M
COUT MURATA 10µF/X7R/6.3V/0805 (GRM21BR70J106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
VIN
15V TO 60V
VOUT
1.8V, 100mA
GND
RT/SYNC
RESET
L1
33µH
EN/UVLO
SS
MODE
VOUT
12V, 100mA
COUT
10µF
GND
VOUT
R1
348kΩ
FB
R2
24.9kΩ
RT/SYNC
R3
69.8kΩ
L1
220µH
RESET
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS5030-224M
COUT MURATA 10µF/X7R/16V/1206 (GRM31CR71C106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
Figure 11. Small Footprint 12V, 100mA Step-Down Regulator
www.maximintegrated.com
Maxim Integrated │ 21
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Package Information
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX17552ATB+
-40°C to +125°C
10 TDFN-EP*
MAX17552AUB+
-40°C to +125°C
10 μMAX
MAX17552AATB+
-40°C to +125°C
10 TDFN-EP*
MAX17552AAUB+
-40°C to +125°C
10 μMAX
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Chip Information
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
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
10 TDFN-EP
T1032N+1
21-0429
90-0082
10 μMAX
U10+5
21-0061
90-0330
PROCESS: BiCMOS
www.maximintegrated.com
Maxim Integrated │ 22
MAX17552/MAX17552A
60V, 100mA, Ultra-Small, High-Efficiency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Revision History
REVISION
NUMBER
REVISION
DATE
0
2/14
Initial release
—
1
6/14
Added statement regarding EN/UVLO connection
11
2
2/15
Updating to include MAX17552A
6/15
Included small solution-size TOCs in Typical Operating Characteristics section
and updated Typical Application Circuit diagrams
3
PAGES
CHANGED
DESCRIPTION
1-20
2, 6–10, 19, 20
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. 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.
© 2015 Maxim Integrated Products, Inc. │ 23
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