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 pulse-
frequency 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 low-
resistance, 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 soft-
start allows the user to reduce the inrush currents. During
overload, the MAX17552 implements a hysteretic cycle-
by-cycle peak-current-limit protection scheme, while the
MAX17552A implements a HICCUP-type overload protec-
tion 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
Benets and Features
Eliminates External Components and Reduces Total Cost
No Schottky—Synchronous Operation for High
E󰀩ciency 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
Congurable Between PFM and Forced-PWM
Modes
Reduces Power Dissipation
22µA No Load Supply Current
Peak E󰀩ciency > 90%
PFM Feature for High Light-Load E󰀩ciency
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
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.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
19-6903; Rev 5; 8/18
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency,
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
EVALUATION KIT AVAILABLE
Click here for production status of specific part numbers.
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
2
SWITCHING FREQUENCY = 220kHz
L1 COILCRAFT LPS5030-224M
COUT MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
CIN MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
LX
RESET
GND
IN
EN/UVLO
SS
MODE
L1
220
µ
H
FB
RT/SYNC
VOUT
R1
261k
R2
49.9k
VOUT
5V, 100mA
VIN
6V TO 60V
C
IN
1
µ
F
C
OUT
10
µ
F
R3
191k
MAX17552/
MAX17552A
R4
22.1
C1
0.22
µ
F
Typical Application Circuit—High-E󰀩ciency 5V, 100mA Regulator
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
Junction Temperature ...................................................... +150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) ....................................... +260°C
PACKAGE TYPE: 10 TDFN
Package Code T1032N+1
Outline Number 21-0429
Land Pattern Number 90-0082
THERMAL RESISTANCE, FOUR-LAYER BOARD
Continuous Power Dissipation (TA = +70°C)
(derate 14.9mW/°C above +70°C) 1188.7mW
Junction to Ambient (θJA) 67.3°C/W
Junction to Case (θJC) 18.2°C/W
PACKAGE TYPE: 10 µMAX
Package Code U10+5
Outline Number 21-0061
Land Pattern Number 90-0330
THERMAL RESISTANCE, FOUR-LAYER BOARD
Continuous Power Dissipation (TA = +70°C)
(derate 8.8mW/°C above +70°C) 707.3mW
Junction to Ambient (θJA) 113.1°C/W
Junction to Case (θJC) 42°C/W
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.
Package 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.
Note 1: Junction temperature greater than +125°C degrades operating lifetimes.
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
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3
Absolute Maximum Ratings (Note 1)
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.
(VIN = 24V, VGND = 0V, VVOUT = 3.3V, VFB = 0.85V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, LX = SS = MODE = RESET = unconnected;
TA = -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 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
INPUT SUPPLY (IN)
Input Voltage Range VIN 4 60 V
Input Shutdown Current IIN-SH VEN/UVLO = 0V, TA = +25°C 0.67 1.2 2.25
µA
Input Supply Current IQ-PFM VMODE = unconnected (Note 3) 18 32
IQ-PWM Normal switching mode, VIN = 24V 245 525 760
EXTERNAL BIAS (VOUT)
VOUT Switchover Threshold 2.96 3.05 3.12 V
ENABLE/UVLO (EN/UVLO)
EN/UVLO Threshold
VENR VEN/UVLO rising 1.2 1.25 1.3
VVENF VEN/UVLO falling 1.1 1.15 1.2
VEN-TRUESD VEN/UVLO falling, true shutdown 0.7
EN/UVLO Leakage Current IEN VEN/UVLO = 1.3V, TA = +25°C -100 +100 nA
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
LX Leakage Current ILX-LKG
VEN = 0V, TA = +25°C,
VLX = (VGND + 1V) to (VIN - 1V) -1 +1 µA
SOFT-START (SS)
Soft-Start Time tSS SS = unconnected 4.4 5.1 5.8 ms
SS Charging Current ISS 4.7 5 5.3 µA
FEEDBACK (FB)
FB Regulation Voltage VFB-REG
MODE = GND 0.786 0.8 0.814 V
MODE = unconnected 0.786 0.812 0.826
FB Input Leakage Current IFB VFB = 1V, TA = 25°C -100 +100 nA
CURRENT LIMIT
Peak Current-Limit Threshold IPEAK-LIMIT 185 210 235 mA
Negative Current-Limit Threshold ISINK-LIMIT
VMODE = GND 79 105 130 mA
VMODE = unconnected 0.01
PFM Current Level IPFM VMODE = unconnected 50 72 90 mA
OSCILLATOR (RT/SYNC)
Switching Frequency fSW
RRT = 422kΩ 90 100 111
kHz
RRT = 191kΩ 205 220 235
RRT = 130kΩ 295 319 340
RRT = 69.8kΩ 540 592 638
RRT = 45.3kΩ 813 900 973
RRT = 19.1kΩ 1.86 2.08 2.3 MHz
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
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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 = -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 2)
Note 2: 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.
Note 3: 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.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Switching Frequency Adjustable
Range
See the Switching Frequency (RT/
SYNC) section for details 100 2200 kHz
SYNC Input Frequency 1.1 x fSW 2200 kHz
SYNC Pulse Minimum O󰀨-Time 40 ns
SYNC Rising Threshold VSYNC-H 1 1.22 1.44 V
Hysteresis VSYNC-HYS 0.115 0.18 0.265
Number of SYNC Pulses to
Enable Synchronization 1 Cycles
TIMING
Minimum On-Time tON-MIN 46 82 128 ns
Maximum Duty Cycle DMAX
fSW ≤ 600kHz,
VFB = 0.98 x VFB-REG
90 94 98
%
fSW > 600kHz,
VFB = 0.98 x VFB-REG
87 92
Hiccup Timeout MAX17552A 51 ms
RESET
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 2.1 ms
RESET Output Level Low IRESET = 1mA 0.23 V
RESET Output Leakage Current VFB = 1.01 x VFB-REG, TA = +25°C 1 µA
MODE
MODE PFM Threshold VMODE-PFM 1 1.22 1.44 V
MODE Hysteresis VMODE-HYS 0.19 V
MODE Internal Pullup Resistor
VMODE = unconnected
(MAX17552) 235
VMODE = unconnected
(MAX17552A) 123
VMODE = GND 1390
THERMAL SHUTDOWN
Thermal-Shutdown Threshold Temperature rising 160 °C
Thermal-Shutdown Hysteresis 20 °C
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
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Electrical Characteristics (continued)
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
0
10
20
30
40
50
60
70
80
90
100
1 10 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(MAX17552)
toc1
VIN = 24V VIN = 36V
VIN = 12V
FIGURE 6 APPLICATION
CIRCUIT, PFM MODE
VOUT = 5V
fSW = 220kHz (RRT = 191k)
0
10
20
30
40
50
60
70
80
90
1 10 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
toc2
VIN = 24V
VIN = 36V
VIN = 12V
FIGURE 6 APPLICATION
CIRCUIT, PFM MODE
V
fSW = 220kHz (RRT = 191k)
OUT = 5V
VIN = 60V
VIN = 48V
0
10
20
30
40
50
60
70
80
90
100
1 10 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
toc3
VIN = 36V
VIN = 12V VIN = 24V
FIGURE 7 APPLICATION
CIRCUIT, PFM MODE
VOUT = 3.3V
(MAX17552)
fSW =220kHz (RRT =191k)
0
10
20
30
40
50
60
70
80
90
100
110 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
toc4
VIN = 12V
VIN = 24V
FIGURE 7 APPLICATION
CIRCUIT, PFM MODE
VOUT = 3.3V
FSW = 220kHz(RRT = 191k)
VIN = 36V
VIN = 48V
VIN = 60V
0
10
20
30
40
50
60
70
80
90
110 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs LOAD CURRENT
(MAX17552A)
toc5
VIN = 24V
VIN = 36V
VIN = 12V FIGURE 6 APPLICATION CIRCUIT,
PFM MODE, VOUT = 5V
FSW = 600kHz (RRT = 69.8k)
VIN = 60V
VIN = 48V
0
10
20
30
40
50
60
70
80
90
100
110 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(MAX17552A)
toc6
VIN = 12V VIN = 24V
FIGURE 7 APPLICATION CIRCUIT,
PFM MODE, VOUT = 3.3V
FSW = 600kHz (RRT = 69.8k)
VIN = 36V
0
10
20
30
40
50
60
70
80
90
100
020406080100
EFFICIENCY (%)
LOAD CURRENT(mA)
EFFICIENCY vs.LOAD CURRENT
toc7
VIN =48V
VIN =36V
VIN =24V
VIN =12V
VIN =60V
(MAX17552)
FIGURE 6APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 220kHz (RRT = 191k)
0
10
20
30
40
50
60
70
80
90
100
020406080100
EFFICIENCY (%)
LOAD CURRENT(mA)
EFFICIENCY vs.LOADCURRENT
(MAX17552A) toc8
VIN =48V
VIN =36V
VIN =24V
VIN =12V
VIN =60V FIGURE 6APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 220kHz (RRT = 191k)
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY VS. LOAD CURRENT
(MAX17552) toc9
VIN = 36V
VIN =48V
VIN = 60V
VIN = 12V
VIN = 24V
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, VOUT = 3
.3V
FSW =220kHz (RRT =191k)
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MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
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.)
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCYVS. LOAD CURRENT
(MAX17552A) toc10
VIN =36V
VIN =48V
VIN =60V
VIN =12V
VIN =24V
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, VOUT = 3.3V
FSW =220kHz (RRT =191k)
0
10
20
30
40
50
60
70
80
90
100
020 40 60 80 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(MAX17552) toc11
VIN = 48V
VIN = 36V
VIN = 24V
VIN = 12V
VIN = 60V FIGURE 6 APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 600kHz (RRT = 69.8k)
0
10
20
30
40
50
60
70
80
90
100
020 40 60 80 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(MAX17552A) toc12
VIN = 48V
VIN = 36V
VIN = 24V
FIGURE 6 APPLICATION CIRCUIT,
PWM MODE, VOUT = 5V
FSW = 600kHz (RRT = 69.8k)
VIN = 60V
VIN = 12V
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
EFFICIENCY (%)
LOAD CURRENT (mA)
EFFICIENCYVS. LOAD CURRENT
(MAX17552)toc13
VIN =36V
VIN =12V
VIN =24V
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, VOUT = 3.3V
FSW =600kHz (RRT =69.8k)
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
EFFICIENCY(%)
LOAD CURRENT (mA)
EFFICIENCYVS. LOAD CURRENT
(MAX17552A)
toc14
V
IN
=36V
V
IN
=12V
V
IN
=24V
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE, V
OUT
= 3.3V
F
SW
=600kHz (R
RT
=69.8k)
4.92
4.95
4.98
5.01
5.04
5.07
5.10
020 40 60 80 100
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
toc15
FIGURE 6 APPLICATION
CIRCUIT, PFM MODE
VIN = 24V
VIN = 12V
VIN = 36V
VIN = 60V
VIN = 48V
3.28
3.30
3.32
3.34
3.36
3.38
3.40
3.42
020 40 60 80 100
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
toc16
FIGURE 7 APPLICATION CIRCUIT,
PFM MODE
VIN = 36V
VIN = 12V,24V
VIN = 48V
VIN = 60V
4.937
4.939
4.941
4.943
4.945
4.947
020 40 60 80 100
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
toc17
VIN = 24V
VIN = 12V
FIGURE6 APPLICATION
CIRCUIT, PWM MODE
VIN = 60V
VIN = 36V VIN = 48V
3.316
3.318
3.320
3.322
3.324
3.326
3.328
3.330
020 40 60 80 100
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
toc18
VIN = 36V
VIN = 12V
FIGURE 7 APPLICATION CIRCUIT,
PWM MODE
VIN = 24V
VIN = 60V
VIN = 48V
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MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
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.)
4.90
4.94
4.98
5.02
5.06
5.10
5.14
0 20 40 60 80 100
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
FIGURE8 APPLICATION
CIRCUIT, PFM MODE
VIN=24V
VIN=12V
VIN=36V
toc19
FIGURE 8 APPLICATION
CIRCUIT, PFM MODE
VIN =24V
VIN =36V
VIN =48V
VIN =60V
VIN =12V
3.20
3.24
3.28
3.32
3.36
3.40
3.44
3.48
020 40 60 80 100
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
toc20
FIGURE 9 APPLICATION CIRCUIT,
PFM MODE
VIN = 36V
VIN = 12V
VIN = 24V
4.949
4.950
4.951
4.952
4.953
4.954
4.955
4.956
4.957
4.958
4.959
4.960
020 40 60 80 100
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
toc21
VIN = 36V
VIN = 24V
VIN = 12V
FIGURE 8 APPLICATION CIRCUIT,
PWM MODE
VIN = 48V VIN = 60V
3.321
3.323
3.325
3.327
3.329
020 40 60 80 100
OUTPUT VOLTAGE (V)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
toc22
VIN = 36V
VIN = 12V
FIGURE 9 APPLICATION CIRCUIT,
PWM MODE
VIN = 24V
0.78
0.79
0.80
0.81
0.82
-40 -20 0 20 40 60 80 100 120
FEEDBACK VOLTAGE (V)
TEMPERATURE (°C)
FEEDBACK VOLTAGE
VS. TEMPERATURE toc23
0
20
40
60
80
100
5 15 25 35 45 55
NO LOAD SUPPLY CURRENT (µA)
INPUT VOLTAGE (V)
NO LOAD SUPPLY CURRENT
vs. INPUT VOLTAGE toc24
PFM MODE
-2.0
-0.5
1.0
2.5
4.0
5 15 25 35 45 55
SHUTDOWN CURRENT (µA)
INPUT VOLTAGE (V)
SHUTDOWN CURRENT
vs. INPUT VOLTAGE toc25
0.5
0.8
1.1
1.4
1.7
2.0
-40 -20 0 20 40 60 80 100 120
SHUTDOWN CURRENT (µA)
TEMPERATURE (°C)
SHUTDOWN CURRENT
vs. TEMPERATURE toc26
0
50
100
150
200
250
5 15 25 35 45 55
SWITCH CURRENT LIMIT (mA)
INPUT VOLTAGE (V)
SWITCH CURRENT LIMIT
vs. INPUT VOLTAGE toc27
SWITCH PEAK
CURRENT LIMIT
SWITCH NEGATIVE
CURRENT LIMIT
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MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
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.)
Typical Operating Characteristics (continued)
0
50
100
150
200
250
-40 -20 0 20 40 60 80 100 120
SWITCH CURRENT LIMIT (mA)
TEMPERATURE (°C)
SWITCH CURRENT LIMIT
vs. TEMPERATURE toc28
SWITCH PEAK
CURRENT LIMIT
SWITCH NEGATIVE
CURRENT LIMIT
90
91
92
93
94
95
96
-40 -20 0 20 40 60 80 100 120
RESET THRESHOLD (%)
TEMPERATURE (°C)
RESET THRESHOLD
vs. TEMPERATURE toc31
RISING
FALLING
100mV/div
50mA/div
toc34
100µs/div
V
OUT
(
AC)
IOUT
LOAD TRANSIENT RESPONSE
PFM OR PWM MODE (LOAD CURRENT
STEPPED FROM 50mA TO 100mA)
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
1.10
1.14
1.18
1.22
1.26
1.30
-40 -20 0 20 40 60 80 100 120
EN/UVLO THRESHOLD VOLTAGE (V)
TEMPERATURE (°C)
EN/UVLO THRESHOLD VOLTAGE
vs. TEMPERATURE toc29
RISING
FALLING
100mV/div
50mA/div
toc32
200µs/div
V
OUT
(
AC)
IOUT
LOAD TRANSIENT RESPONSE,
PFM MODE (LOAD CURRENT STEPPED
FROM 5mA to 50mA)
FIGURE6
APPLICATION
CIRCUIT
VOUT=5V
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
100mV/div
50mA/div
toc35
100µs/div
V
OUT
(
AC)
IOUT
LOAD TRANSIENT RESPONSE
PFM OR PWM MODE (LOAD CURRENT
STEPPED FROM 50mA TO 100mA)
FIGURE 7
APPLICATION CIRCUIT
VOUT = 3.3V
0
200
400
600
800
1000
-40 -20 0 20 40 60 80 100 120
SWITCHING FREQUENCY (KHz)
TEMPERATURE (°C)
SWITCHING FREQUENCY
vs. TEMPERATURE toc30
RT=191k
RT= 69.8k
RT= 45.3k
RT=422k
100mV/div
50mA/div
toc33
200µs/div
V
OUT
(
AC)
IOUT
LOAD TRANSIENT RESPONSE
PFM MODE (LOAD CURRENT STEPPED
FROM 5mA to 50mA)
FIGURE7
APPLICATION
CIRCUIT
VOUT=3.3V
FIGURE 7
APPLICATION CIRCUIT
VOUT = 3.3V
100mV/div
50mA/div
toc36
100µs/div
V
OUT
(
AC)
IOUT
LOAD TRANSIENT RESPONSE
PWM MODE (LOAD CURRENT STEPPED
FROM NO-LOAD TO 50mA)
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
9
(VIN = 24V, VGND = 0V, VOUT = 3.3V, VEN/UVLO = 1.5V, RT/SYNC = 191kΩ, CIN = 1μF, TA = +25°C unless otherwise noted.)
100mV/
div
toc37
100µs/div
V
OUT
(
AC)
IOUT
LOAD TRANSIENT RESPONSE
PWM MODE (LOAD CURRENT STEPPED
FROM NO-LOAD TO 50mA)
50mA/div
FIGURE 7
APPLICATION CIRCUIT
VOUT = 3.3V
2V/div
5V/div
toc43
2ms/div
V
EN/UVLO
V
OUT
50mA/div
5V/div
SHUTDOWN WITH ENABLE
V
RESET
I
OUT
FIGURE 6
APPLICATION CIRCUIT
V
OUT
= 5V
100mV/div
toc38
10µs/div
V
OUT
(
AC)
ILX
SWITCHING WAVEFORMS
(PFM MODE)
100mA/div
LX
10V/div
FIGURE 6 APPLICATION CIRCUIT
VOUT = 5V,LOAD = 20mA
1V/div
5V/div
toc44
1ms/div
VEN/UVLO
VOUT
5V/div
SOFT START WITH 3V PREBIAS
VRESET
FIGURE 6
APPLICATION CIRCUIT
NO LOAD
PWM MODE
20mV/div
toc39
4µs/div
V
OU
T
(
AC
)
ILX
FULL LOAD-SWITCHING WAVEFORMS
(PWM OR PFM MODE)
100mA/div
LX
10V/div
FIGURE 6 APPLICATION CIRCUIT
VOUT = 5V, LOAD = 100mA
10V/div
2V/div
toc45
4µs/div
VRT/SYNC
VLX
EXTERNAL SYNCHRONIZATION WITH
300kHz CLOCK FREQUENCY
FIGURE 6
APPLICATION
CIRCUIT
100mA LOAD
PWM MODE
20mV/div
toc40
4µs/div
V
OUT
(
AC)
ILX
NO LOAD SWITCHING WAVEFORMS
(PWM MODE)
100mA/div
LX
10V/div
FIGURE 6 APPLICATION CIRCUIT
VOUT = 5V
2V/div
5V/div
toc41
1ms/div
VEN/UVLO
VOUT
50mA/div
5V/div
SOFT START
IOUT
VRESET
FIGURE 6
APPLICATION
CIRCUIT
VOUT = 5V
1V/div
2V/div
toc42
1ms/div
VEN/UVLO
VOUT
50mA/div
5V/div
SOFT START
IOUT
VRESET
FIGURE 7
APPLICATION
CIRCUIT
VOUT = 3.3V
Maxim Integrated
10
www.maximintegrated.com
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
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.)
100mA/div
toc46
1ms/div
VOUT
ILX
5V/div
OVERLOAD PROTECTION
(MAX17552)
FIGURE 6
APPLICATION CIRCUIT
VOUT = 5V
100mA/div
toc47
20ms/div
OVERLOAD PROTECTION
(MAX17552A)
ILX
toc48
BODE PLOT
FIGURE 6 APPLICATION CIRCUIT
VOUT = 5V
FCR = 8.5KHz,
PHASE MARGIN = 64°
GAIN
PHA
50
40
30
20
10
-10
-20
-30
-40
-50
0
180
1k 10k100k
144
108
72
36
-36
-72
-108
-144
-180
0
SE
toc50
CONDUCTED EMI CURVE
(5V OUTPUT, 100mA LOAD CURRENT)
0.15 110 30
AVERAGE
EMISSIONS
PEAK
EMISSIONS
CONDUCTED EMI (dBµV)
FREQUENCY (MHz)
10
20
30
40
50
60
70
QUASI-PEAK LIMIT
AVERAGE LIMIT
80
toc49
BODE PLOT
FIGURE 7 APPLICATION CIRCUIT
VOUT = 3.3V
FCR = 10.5KHz,
PHASE MARGIN = 61°
GAIN
PHASE
50
40
30
20
10
-10
-20
-30
-40
-50
0
180
1k 10k100k
144
108
72
36
-36
-72
-108
-144
-180
0
Class B limit
Horizontal limit
Vertical limit
toc51
RADIATED EMI CURVE
(5V OUTPUT, 100mA LOAD CURRENT)
30
100
500
1000
10
20
30
40
50
60
70
0
-10
AMPLITUDE (dBuV/m)
FREQUENCY (MHz)
CLASS B LIMIT
HORIZONTAL
VERTICAL EMISSION
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
11
Typical Operating Characteristics (continued)
MAX17552/
MAX17552A
TOP VIEW
1
+
3 4
LX
MODE
VOUT
RESET
2
GND
IN RT/
SYNC
SSEN/
UVLO
TDFN
3mm x 2mm
5
FB
10 8 79 6
10
2
3
4
5
9
8
7
6
GND
MODE
RESET
VOUT
FB
SS
RT/SYNC
EN/UVLO
µMAX
3mm x 3mm
+
MAX17552/
MAX17552A
1 LXIN
PIN NAME FUNCTION
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 xed-frequency PWM
operation. Leave MODE unconnected for light-load PFM operation.
9 GND 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.
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.
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
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12
Pin Description
Pin Conguration
EN/UVLO
1.25V
INTERNAL
LDO
REGULATOR
PFM/PWM
CONTROL
LOGIC
1.22V
MODE
THERMAL
SHUTDOWN
MODE SELECT
CHIPEN
FB
PWM
CS
SLOPE
INTERNAL OR
EXTERNAL
SOFT-START
CONTROL
ERROR
AMPLIFIER
OSCILLATOR
CLK
SLOPE
PEAK-LIMIT
PFM
HIGH-SIDE
DRIVER
CURRENT-
SENSE
LOGIC
LOW-SIDE
DRIVER
DH
DL
SINK-LIMIT
CS
LX
RESET
GND
SS
RT/SYNC
VCC_INT
IN
V
OUT
VCC_INT
POK
CLK
CURRENT-
SENSE
AMPLIFIER
CURRENT
SENSE
AMPLIFIER
2ms
DELAY
0.76V
NEGATIVE
CURRENT
REF
FB
MAX17552/MAX17552A
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
13
Block Diagram
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, peak-
current-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 high-
side 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 addi-
tionally 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
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 UVLO-
adjustment 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.
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
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14
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:
TSW
42000
Rf
=
The switching frequency in ranges of 130kHz to 160kHz
and 230kHz to 280kHz are not allowed for user pro-
gramming 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.
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 rat-
ing 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 volt-
age should be calculated as follows:
Figure 1. Synchronization to an External Clock
CLOCK
SOURCE
DUTY
47pF
R
T
RT/SYNC
V
LOGIC-LOW
MAX17552/
MAX17552A
V
LOGIC-HIGH
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
15
OUT OUT DCR
INMIN OUT
MAX
V (I (R 2.6))
V (I 2.5)
D
+
=
OUT
INMAX ONMIN SW
V
V
tf
=×
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 worst-
case 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 contin-
ues 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 consecu-
tive 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 dissi-
pation 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.
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:
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:
OUT
OUT IN
SW
V
1000 V 1 V
IfL

××


∆= ×
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 satu-
ration current rating should be the maximum of either
0.235A or the value from the equation:
INMAX ON MIN
SAT
Vt
I 0.15 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 com-
monly 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 rela-
tively 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.
OUT
SW
10000 x V
L = f
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
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16
Output Capacitor Selection
Small ceramic X7R-grade output capacitors are recom-
mended 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 output-
voltage deviation is less than 3%. Calculate the minimum
required output capacitance from the following equations:
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.
t
SS
> 0.05 x C
OUT
x V
OUT
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:
SS SS
C 6.25 t= ×
where tSS is in milliseconds and CSS is in nanofarads.
Setting the Input Undervoltage-Lockout Level
The devices offer an adjustable input undervoltage-
lockout 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:
INU
R1 1.25
R2 (V - 1.25)
×
=
where VINU is the voltage at which the device is required
to turn on.
If the EN/UVLO pin is driven from an external signal
source, a series resistance of minimum 1kΩ is recom-
mended to be placed between the signal source output
and the EN/UVLO pin to reduce voltage ringing on the
line.
Frequency
Range
(kHz)
Minimum Output
Capacitance
(μF)
100 to 130
OUT
50
V
160 to 230
OUT
25
V
280 to 2200
OUT
17
V
Figure 2. Adjustable EN/UVLO Network Figure 3. Setting the Output Voltage
R2
EN/UVLO
IN
MAX17552/
MAX17552A
R1
VIN
R2
FB
MAX17552/
MAX17552A
R1
VOUT
GND
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
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17
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 resistor-
divider 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:
OUT
V
R1 R2 1
0.8

= ×


Transient Protection
In applications where fast line transients or oscillations
with a slew rate in excess of 15V/µs are expected dur-
ing 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.
Power Dissipation
At a particular operating condition, the power losses that
lead to temperature rise of the device are estimated as
follows:
2
LOSS OUT OUT DCR
1
P P - 1 - (I R )


=××


η


OUT OUT OUT
P VI
= ×
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 effi-
ciency 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:
( )
J A JA LOSS
TT P= ×
where θJA is the junction-to-ambient thermal impedance
of the package.
Junction temperature greater than +125°C degrades
operating lifetimes.
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
For a sample PCB layout that ensures the first-pass
success, refer to the MAX17552/MAX17552A evaluation
kit data sheet.
Figure 4. Transient Protection
4.7Ω
IN
MAX17552/
MAX17552A
GND
CIN
1
µF
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
18
Figure 5. Layout Guidelines
C
IN
C
OUT
U1
V
IN
PLANE
GND PLANE
V
OUT
PLANE
Vias to Bottom-Side Ground Plane
Vias to V
OUT
R1
R2
R3
C
SS
L1
R4
R5
R6
Vias to RESET
LX
RESET
GND
IN
EN/UVLO
MAX17552/
MAX17552A
V
IN
V
OUT
SS
MODE
L1
C
OUT
FB
RT/SYNC
VOUT
R1
R2
R3
R4
R5
C
IN
V
OUT
R6
C
SS
GND PLANE
IN
EN/UVLO
RT/SYNC
SS
FB
VOUT
RESET
MODE
GND
LX
R7
C
F
R7 C
F
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
19
Figure 6. High-Efficiency 5V, 100mA Regulator Figure 7. High-Efficiency 3.3V, 100mA Regulator
Figure 8. Small Footprint 5V, 100mA Regulator
SWITCHING FREQUENCY = 220kHz
L1 COILCRAFT LPS5030-224M
C
OUT
MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
C
IN
MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
LX
RESET
GND
IN
EN/UVLO
SS
MODE
L1
220
µ
H
FB
RT/SYNC
V
OUT
R1
261k
R2
49.9k
V
OUT
5V, 100mA
V
IN
6V TO 60V
C
IN
1
µ
F
C
OUT
10
µ
F
R3
191k
MAX17552/
MAX17552A
R4
22.1
C1
0.22
µ
F
SWITCHING FREQUENCY = 220kHz
L1 COILCRAFT LPS5030-154M
C
OUT
MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
C
IN
MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
LX
RESET
GND
IN
EN/UVLO
SS
MODE
L1
150
µ
H
FB
RT/SYNC
V
OUT
R1
158k
R2
49.9k
V
OUT
3.3V, 100mA
V
IN
4V TO 60V
C
IN
1
µ
F
C
OUT
10
µ
F
R3
191k
MAX17552/
MAX17552A
R4
22.1
C1
0.22
µ
F
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS3015-104M
C
OUT
MURATA 10µF/X7R/6.3V/0805 (GRM21BR70J106K)
C
IN
MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
LX
RESET
GND
IN
EN/UVLO
SS
MODE
L1
100
µ
H
FB
RT/SYNC
V
OUT
R1
261k
R2
49.9k
V
OUT
5V, 100mA
V
IN
6V TO 60V
C
IN
1
µ
F
C
OUT
10
µ
F
R3
69.8k
MAX17552/
MAX17552A
R4
22.1
C1
0.22
µ
F
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
20
Typical Application Circuits
Figure 10. Small Footprint 1.8V, 100mA RegulatorFigure 9. Small Footprint 3.3V, 100mA Regulator
Figure 11. Small Footprint 12V, 100mA Step-Down Regulator
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS3015-683M
C
OUT
MURATA 10µF/X7R/6.3V/0805 (GRM21BR70J106K)
C
IN
MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
LX
RESET
GND
IN
EN/UVLO
SS
MODE
L1
68
µ
H
FB
RT/SYNC
V
OUT
R1
158k
R2
49.9k
V
OUT
3.3V, 100mA
V
IN
4V TO 45V
C
IN
1
µ
F
C
OUT
10
µ
F
R3
69.8k
MAX17552/
MAX17552A
R4
22.1
C1
0.22
µ
F
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS3015-333M
C
OUT
MURATA 10µF/X7R/6.3V/1206 (GRM31CR70J106K)
C
IN
MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
LX
RESET
GND
IN
EN/UVLO
SS
MODE
L1
33
µ
H
FB
RT/SYNC
V
OUT
R1
127k
R2
100k
V
OUT
1.8V, 100mA
V
IN
4V TO 24V
C
IN
1
µ
F
C
OUT
10
µ
F
R3
69.8k
MAX17552/
MAX17552A
SWITCHING FREQUENCY = 600kHz
L1 COILCRAFT LPS5030-224M
C
OUT
MURATA 10µF/X7R/16V/1206 (GRM31CR71C106K)
C
IN
MURATA 1µF/X7R/100V/1206 (GRM31CR72A105K)
LX
RESET
GND
IN
EN/UVLO
SS
MODE
L1
220
µ
H
FB
RT/SYNC
V
OUT
R1
348k
R2
24.9k
V
OUT
12V, 100mA
V
IN
15V TO 60V
C
IN
1
µ
F
C
OUT
10
µ
F
R3
69.8k
MAX17552/
MAX17552A
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
21
Typical Application Circuits (continued)
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
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
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
www.maximintegrated.com Maxim Integrated
22
Chip Information
PROCESS: BiCMOS
Ordering Information
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 2/14 Initial release
1 6/14 Added statement regarding EN/UVLO connection 11
2 2/15 Updating to include MAX17552A 1-20
3 6/15 Included small solution-size TOCs in Typical Operating Characteristics section
and updated Typical Application Circuit diagrams
2, 6–10,
19, 20
4 9/17
Updated Features and Benets, Mode Selection (MODE), Setting the Input
Undervoltage-Lockout Level, and Power Dissipation sections. Updated the
Electrical Characteristics table global characteristics. Inserted new Note 1 and
updated Absolute Maximum Ratings, and added TOC50 and TOC51.
1, 3–5,
11, 14,
17–18
5 8/18 Updated the Mode Selection (MODE) section. 14
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 specications 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. © 2018 Maxim Integrated Products, Inc.
23
MAX17552/MAX17552A 60V, 100mA, Ultra-Small, High-E󰀩ciency
Synchronous Step-Down DC-DC Converter
with 22µA No-Load Supply Current
Revision History
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