MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter General Description

MAX17501 60V, 500mA, Ultra-Small, High-Efficiency, Synchronous Step-Down DC-DC Converter General Description
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
General Description
The MAX17501 high-efficiency, high-voltage, synchro­nous
step-down DC-DC converter with integrated MOSFETs
operates over a 4.5V to 60V input voltage range. This
device is offered in a fixed 3.3V, 5V, or adjustable output
voltage (0.9V to 92%VIN) while delivering up to 500mA
of current. The output voltage is accurate to within
±1.7% over -40°C to +125°C. The MAX17501 is available in a compact TDFN package. Simulation models are
available.
The device features peak-current-mode control with
pulse-width modulation (PWM). Users can choose devices with either pulse frequency modulation (PFM) or forced
PWM scheme. PFM devices skip pulses at light load for
higher efficiency, while forced-PWM devices operate with
fixed switching frequency at any load for noise sensitive-applications. The low-resistance, on-chip MOSFETs
ensure high efficiency at full load and simplify the layout.
A programmable soft-start feature allows users to reduce
input inrush current. The device also incorporates an
output enable/undervoltage lockout pin (EN/UVLO) that
allows the user to turn on the part at the desired inputvoltage level. An open-drain RESET pin provides a
delayed power-good signal to the system upon achieving
successful regulation of the output voltage.
Applications
●
●
●
●
●
●
Industrial Process Control
HVAC and Building Control
Base Station, VOIP, Telecom
Home Theatre
Battery-Powered Equipment
General-Purpose Point-of-Load
19-6244; Rev 5; 11/14
Benefits and Features
● Eliminates External Components and Reduce Total
Cost
•
No Schottky-Synchronous Operation for High
Efficiency and Reduced Cost
•
Internal Compensation and Feedback Divider for
3.3V and 5V Fixed Outputs
•All-Ceramic Capacitors, Ultra-Compact Layout
● Reduces Number of DC-DC Regulators to Stock
•
Wide 4.5V to 60V Input Voltage Range
•
0.9V to 92%VIN Adjustable Output Voltage
•
Delivers up to 500mA
•
600kHz and 300kHz Switching Frequency Options
•
Available in a 10-Pin, 3mm x 2mm TDFN Package
● Reduces Power Dissipation
•
Peak Efficiency > 90%
•
PFM Feature for High Light-Load Efficiency
•
Shutdown Current = 0.9μA (typ)
● Operates Reliably in Adverse Industrial Environments
•
Hiccup-Mode Current Limit, Sink Current Limit,
and Autoretry Startup
•
Built-In Output-Voltage Monitoring (Open-Drain
RESET Pin)
•
Resistor-Programmable EN/UVLO Threshold
•
Adjustable Soft-Start and Prebiased Power-Up
•
-40°C to +125°C Industrial Temperature Range
Ordering Information appears at end of data sheet.
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Absolute Maximum Ratings
VIN to GND.............................................................-0.3V to +70V
EN/UVLO to GND.......................................-0.3V to (VIN + 0.3V)
LX to PGND................................................-0.3V to (VIN + 0.3V)
FB, RESET, COMP, SS to GND..............................-0.3V to +6V
VCC to GND..............................................................-0.3V to +6V
GND to PGND.......................................................-0.3V to +0.3V
LX Total RMS Current......................................................... ±1.6A
Output Short-Circuit Duration.....................................Continuous
Continuous Power Dissipation (TA = +70°C)
(derate 14.9mW/°C above +70°C) (multilayer board)..1188.7mW
Operating Temperature Range......................... -40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range............................. -65°C to +160°C
Lead Temperature (soldering, 10s).................................+300°C
Soldering Temperature (reflow).......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Package Thermal Characteristics (Note 1)
TDFN
Junction-to-Ambient Thermal Resistance (θJA)........67.3°C/W
Junction-to-Case Thermal Resistance (θJC).............18.2°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 = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
60
V
INPUT SUPPLY (VIN)
Input Voltage Range
VIN
IIN-SH
Input Supply Current
4.5
VEN = 0V, shutdown mode
IIN-HIBERNATE VFB = 1.03 x VOUT, MAX17501A/B
0.9
3.5
90
145
4.75
6.75
2.5
3.6
µA
IIN-SW
Normal
MAX17501E/F/G
switching mode,
MAX17501H
no load
VENR
VEN rising
1.194
1.218
1.236
VENF
VEN falling
1.114
1.135
1.156
V
8
200
nA
4.65
5
5.35
V
40
80
mA
mA
ENABLE/UVLO (EN/UVLO)
EN Threshold
VEN-TRUESD
EN Input Leakage Current
VEN falling, true shutdown
IEN
VEN = VIN = 60V, TA = +25°C
VCC
6V < VIN < 12V, 0mA < IVCC < 10mA,
12V < VIN < 60V, 0mA < IVCC < 2mA
0.7
LDO
VCC Output Voltage Range
VCC Current Limit
VCC Dropout
VCC UVLO
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IVCC-MAX
VCC = 4.3V, VIN = 12V
15
VCC-DO
VIN = 4.5V, IVCC = 5mA
4.1
VCC-UVR
VCC rising
3.85
4
4.15
VCC-UVF
VCC falling
3.55
3.7
3.85
V
V
Maxim Integrated │ 2
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Electrical Characteristics (continued)
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
0.55
0.85
UNITS
POWER MOSFETs
TA = +25°C
High-Side pMOS On-Resistance
RDS-ONH
ILX = 0.5A
(sourcing)
Low-Side nMOS On-Resistance
RDS-ONL
ILX = 0.5A
(sinking)
LX Leakage Current
ILX_LKG
VEN = 0V, TA = +25°C,
VLX = (VPGND + 1V) to (VIN - 1V)
TA = TJ = +125°C
(Note 3)
1.2
TA = +25°C
0.2
TA = TJ = +125°C
(Note 3)
Ω
0.35
0.47
Ω
1
µA
SOFT-START (SS)
Charging Current
ISS
VSS = 0.5V
4.7
5
5.3
µA
0.884
0.9
0.916
V
MAX17501A/E, VFB
= 3.3V
6.8
12
17
MAX17501B/F, VFB
= 5V
6.8
12
17
FEEDBACK (FB/VO)
FB Regulation Voltage
FB Input Bias Current
VFB_REG
IFB
MAX17501G/H
TA = +25NC
µA
MAX17501G/H, VFB
= 0.9V
100
nA
OUTPUT VOLTAGE (VOUT)
Output Voltage Accuracy
VOUT
MAX17501A
3.248
3.380
3.448
MAX17501B
4.922
5.121
5.225
MAX17501E
3.248
3.3
3.352
MAX17501F
4.922
5
5.08
ICOMP = ±2.5µA, MAX17501G/H
510
590
650
µS
V
TRANSCONDUCTANCE AMPLIFIER (COMP)
Transconductance
GM
COMP Source Current
ICOMP_SRC
MAX17501G/H
19
32
55
µA
COMP Sink Current
ICOMP_SINK
MAX17501G/H
19
32
55
µA
RCS
MAX17501G/H
0.9
1
1.1
V/A
Current-Sense Transresistance
CURRENT LIMIT
Peak Current-Limit Threshold
IPEAK-LIMIT
0.64
0.76
0.86
A
Runaway Current-Limit Threshold
IRUNAWAY-
0.65
0.78
0.905
A
Sink Current-Limit Threshold
ISINK-LIMIT
PFM Current-Limit Threshold
IPFM
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LIMIT
MAX17501A/B
MAX17501E/F/G/H
MAX17501A/B
0.03
0.3
0.35
0.125
0.4
A
A
Maxim Integrated │ 3
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Electrical Characteristics (continued)
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
VFB > VOUT- MAX17501A/B/E/F/G
MAX17501H
HICF
560
600
640
280
300
320
VFB < VOUT-HICF
280
300
320
UNITS
TIMINGS
Switching Frequency
fSW
Events to Hiccup after Crossing
Runaway Current Limit
VOUT Undervoltage Trip Level to
Cause Hiccup
1
VOUT-HICF
VSS > 0.95V (soft-start is done)
69.14
HICCUP Timeout
Minimum On-Time
Maximum Duty Cycle
71.14
Event
73.14
32,768
tON_MIN
DMAX
VFB = 0.98 x MAX17501A/B/E/F/G
VFB-REG
MAX17501H
%
Cycles
75
120
92
94
96
96.5
97.5
98.5
LX Dead Time
kHz
5
ns
%
ns
RESET
RESET Output Level Low
IRESET = 1mA
0.02
V
RESET Output Leakage
Current High
VFB = 1.01 x VFB-REG, TA = +25°C
0.45
µA
VOUT Threshold for RESET Falling
VOUT-OKF
VFB falling
90.5
92.5
94.5
%
VOUT Threshold for RESET Rising
VOUT-OKR
VFB rising
93.5
95.5
97.5
%
RESET Delay After FB Reaches
95% Regulation
VFB rising
1024
Cycles
Temperature rising
165
°C
10
°C
THERMAL SHUTDOWN
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
Note 2: All limits are 100% tested at +25°C. Limits over temperature are guaranteed by design.
Note 3: Guaranteed by design, not production tested.
www.maximintegrated.com
Maxim Integrated │ 4
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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.)
60
VIN = 36V
VIN = 12V
MAX17501 toc03
65
60
55
VIN = 48V
50
1
10
45
100
50 100 150 200 250 300 350 400 450 500
OUTPUT VOLTAGE vs. LOAD CURRENT
(MAX17501A)
OUTPUT VOLTAGE vs. LOAD CURRENT
(MAX17501B)
VIN = 36V
VIN = 48V
VIN = 24V
5.20
3.40
VIN = 36V
3.35
VIN = 24V
VIN = 12V
3.30
5.15
MAX17501 toc06
3.45
50
VIN = 12V
VIN = 24V
5.10
VIN = 36V
5.05
VIN = 48V
5.00
4.95
3.25
50 100 150 200 250 300 350 400 450 500
0
4.90
50 100 150 200 250 300 350 400 450 500
0
50 100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
LOAD CURRENT (mA)
OUTPUT VOLTAGE vs. LOAD CURRENT
(MAX17501E)
OUTPUT VOLTAGE vs. LOAD CURRENT
(MAX17501F)
SHUTDOWN CURRENT
vs. TEMPERATURE
OUTPUT VOLTAGE (V)
5.03
3.310
3.305
3.300
VIN = 12V
3.295
VIN = 24V
VIN = 36V
5.02
5.01
5.00
4.99
VIN = 48V VIN = 36V VIN = 24V VIN = 12V
4.98
4.97
50 100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
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4.95
1.05
1.00
0.95
0.90
0.85
0.80
0.75
4.96
0
1.10
MAX17501 toc09
5.04
SHUTDOWN CURRENT (µA)
MAX17501 toc07
5.05
MAX17501 toc08
LOAD CURRENT (mA)
3.315
OUTPUT VOLTAGE (V)
VIN = 36V
VIN = 12V
EFFICIENCY vs. LOAD CURRENT
(MAX17501F)
60
3.290
VIN = 24V
70
LOAD CURRENT (mA)
80
3.320
75
LOAD CURRENT (mA)
90
40
80
LOAD CURRENT (mA)
VIN = 12V
70
VIN = 36V
40
100
85
OUTPUT VOLTAGE (V)
100
10
60
30
90
MAX17501 toc05
1
VIN = 24V
VIN = 24V
70
50
OUTPUT VOLTAGE (V)
40
VIN = 12V
80
95
EFFICIENCY (%)
70
50
EFFICIENCY (%)
EFFICIENCY (%)
80
90
MAX17501 toc04
EFFICIENCY (%)
90
30
100
MAX17501 toc01
100
EFFICIENCY vs. LOAD CURRENT
(MAX17501E)
EFFICIENCY vs. LOAD CURRENT
(MAX17501B)
MAX17501 toc02
EFFICIENCY vs. LOAD CURRENT
(MAX17501A)
0
50 100 150 200 250 300 350 400 450 500
LOAD CURRENT (mA)
0.70
-40 -20
0
20
40
60
80
100 120
TEMPERATURE (°C)
Maxim Integrated │ 5
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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.)
80
60
0
20
40
60
80
100 120
CURRENT LIMIT (A)
60
80
1.18
1.17
1.16
FALLING
THRESHOLD
1.15
1.14
1.13
1.12
100 120
MAX17501 toc12
MAX17501 toc11
40
RISING
THRESHOLD
-40 -20
0
20
40
60
80
100 120
FEEDBACK VOLTAGE
vs. TEMPERATURE
OUTPUT VOLTAGE (V)
-40 -20
0
20
40
60
80
100 120
5.000
4.975
4.950
-40 -20
0
20
40
60
80
100 120
MAX17501 toc15
5.025
0.92
FEEDBACK VOLTAGE (V)
5.050
MAX17501 toc14
NO-LOAD OUTPUT VOLTAGE
vs. TEMPERATURE (MAX17501F)
0.91
0.90
0.89
0.88
-40 -20
0
20
40
60
80
100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
PEAK AND RUNAWAY CURRENT LIMIT
vs. TEMPERATURE
SWITCHING FREQUENCY
vs. TEMPERATURE
NO-LOAD SOFT-START FROM EN/UVLO
(MAX17501A)
0.75
RUNAWAY
CURRENT
LIMIT
PEAK
CURRENT
LIMIT
-40 -20
0
20
40
60
80
TEMPERATURE (°C)
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100 120
700
MAX17501 toc18
MAX17501 toc17
MAX17501 toc16
TEMPERATURE (°C)
0.80
0.60
20
1.19
NO-LOAD OUTPUT VOLTAGE
vs. TEMPERATURE (MAX17501E)
0.85
0.65
0
1.20
TEMPERATURE (°C)
3.275
0.70
-40 -20
1.21
TEMPERATURE (°C)
3.300
0.90
4.85
1.22
TEMPERATURE (°C)
3.325
3.250
4.90
4.80
SWITCHING FREQUENCY (kHz)
3.350
-40 -20
4.95
EN/UVLO THRESHOLD
vs. TEMPERATURE
1.23
EN/UVLO THRESHOLD VOLTAGE (V)
100
5.00
NO-LOAD SWITCHING CURRENT (mA)
MAX17501 toc10
120
40
OUTPUT VOLTAGE (V)
NO-LOAD SWITCHING CURRENT vs. TEMPERATURE
(FORCED-PWM OPERATION)
MAX17501 toc13
NO-LOAD SWITCHING CURRENT (µA)
140
NO-LOAD SWITCHING CURRENT
vs. TEMPERATURE (PFM OPERATION)
600
EN/UVLO
2V/div
500
400
VOUT
1V/div
RESET
2V/div
300
200
-40 -20
0
20
40
60
80
100 120
1ms/div
TEMPERATURE (°C)
Maxim Integrated │ 6
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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.)
NO-LOAD SOFT-START FROM EN/UVLO
(MAX17501B)
MAX17501 toc19
FULL-LOAD SOFT-START/SHUTDOWN FROM EN/UVLO
(MAX17501E)
MAX17501 toc20
EN/UVLO
2V/div
EN/UVLO
2V/div
VOUT
2V/div
VOUT
1V/div
IOUT
200mA/div
RESET
2V/div
RESET
5V/div
1ms/div
1ms/div
FULL-LOAD SOFT-START/SHUTDOWN FROM EN/UVLO
(MAX17501F)
NO-LOAD SOFT-START FROM VIN
(MAX17501A)
MAX17501 toc21
MAX17501 toc22
VIN
20V/div
EN/UVLO
2V/div
VOUT
2V/div
IOUT
200mA/div
VOUT
1V/div
RESET
2V/div
RESET
5V/div
1ms/div
400µs/div
NO-LOAD SOFT-START FROM VIN
(MAX17501B)
FULL-LOAD SOFT-START FROM VIN
(MAX17501E)
MAX17501 toc23
VIN
20V/div
VIN
20V/div
IOUT
200mA/div
VOUT
2V/div
VOUT
1V/div
RESET
2V/div
RESET
5V/div
400µs/div
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MAX17501 toc24
400µs/div
Maxim Integrated │ 7
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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.)
FULL-LOAD SOFT-START FROM VIN
(MAX17501F)
SOFT-START WITH 2V PREBIAS
(MAX17501A)
MAX17501 toc25
VIN
20V/div
MAX17501 toc26
EN/UVLO
2V/div
VOUT
1V/div
IOUT
200mA/div
VOUT
2V/div
RESET
5V/div
RESET
2V/div
400µs/div
400µs/div
SOFT-START WITH 2.5V PREBIAS
(MAX17501B)
SOFT-START WITH 2V PREBIAS
(MAX17501E)
MAX17501 toc27
EN/UVLO
2V/div
MAX17501 toc28
EN/UVLO
2V/div
VOUT
1V/div
VOUT
1V/div
RESET
5V/div
RESET
2V/div
400µs/div
400µs/div
SOFT-START WITH 2.5V PREBIAS
(MAX17501F)
MAX17501 toc29
LOAD TRANSIENT RESPONSE OF MAX17501A
(LOAD CURRENT STEPPED FROM 5mA TO 255mA)
MAX17501 toc30
VOUT (AC)
100mV/div
EN/UVLO
2V/div
VOUT
1V/div
IOUT
100mA/div
RESET
5V/div
400µs/div
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200µs/div
Maxim Integrated │ 8
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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.)
LOAD TRANSIENT RESPONSE OF MAX17501B
(LOAD CURRENT STEPPED FROM 5mA TO 255mA)
MAX17501 toc31
LOAD TRANSIENT RESPONSE OF MAX17501E
(LOAD CURRENT STEPPED FROM NO-LOAD TO 250mA)
MAX17501 toc32
VOUT (AC)
100mV/div
VOUT (AC)
50mV/div
IOUT
100mA/div
IOUT
100mA/div
200µs/div
20µs/div
LOAD TRANSIENT RESPONSE OF MAX17501F
(LOAD CURRENT STEPPED FROM NO-LOAD TO 250mA)
LOAD TRANSIENT RESPONSE OF MAX17501E
(LOAD CURRENT STEPPED FROM 250mA TO 500mA)
MAX17501 toc33
MAX17501 toc34
VOUT (AC)
50mV/div
VOUT (AC)
100mV/div
IOUT
200mA/div
IOUT
100mA/div
20µs/div
20µs/div
LOAD TRANSIENT RESPONSE OF MAX17501F
(LOAD CURRENT STEPPED FROM 250mA TO 500mA)
MAX17501 toc35
MAX17501 toc36
VOUT (AC)
50mV/div
VOUT (AC)
100mV/div
ILX
500mA/div
IOUT
200mA/div
LX
10V/div
20µs/div
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SWITCHING WAVEFORMS OF MAX17501F
AT 500mA LOAD
2µs/div
Maxim Integrated │ 9
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 24V, VGND = VPGND = 0V, CVIN = CVCC = 1μF, VEN = 1.5V, CSS = 3300pF, VFB = 0.98 x VOUT, LX = unconnected, 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.)
SWITCHING WAVEFORMS OF MAX17501A
AT 15mA LOAD
OUTPUT OVERLOAD PROTECTION
OF MAX17501F
MAX17501 toc37
VOUT (AC)
100mV/div
MAX17501 toc38
VOUT
2V/div
LX
10V/div
ILX
100mA/div
IOUT
200mA/div
10µs/div
20ms/div
BODE PLOT OF MAX17501E
AT 500mA LOAD
BODE PLOT OF MAX17501F
AT 500mA LOAD
MAX17501 toc39
fCR = 51kHz
PM = 55°
4
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5 6 7 8 9 1
MAX17501 toc40
fCR = 49.8kHz
PM = 62°
2
4
5 6 7 8 9 1
2
Maxim Integrated │ 10
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Pin Configuration
TOP VIEW
MAX17501
10
LX
9
GND
3
8
RESET
VCC
4
7
N.C./COMP
FB/VO
5
6
SS
PGND
1
VIN
2
EN/UVLO
+
EP*
TDFN
(3mm x 2mm)
*EP = EXPOSED PAD. CONNECT TO GND
Pin Description
PIN
NAME
FUNCTION
1
PGND
Power Ground. Connect PGND externally to the power ground plane. Connect GND and PGND pins
together at the ground return path of the VCC bypass capacitor.
2
VIN
3
EN/UVLO
4
VCC
5
FB/VO
6
SS
Power-Supply Input. The input supply range is from 4.5V to 60V.
Enable/Undervoltage Lockout Input. Drive EN/UVLO high to enable the output voltage. Connect to the
center of the resistive divider between VIN and GND to set the input voltage (undervoltage threshold) at
which the device turns on. Pull up to VIN for always on.
5V LDO Output. Bypass VCC with 1µF ceramic capacitance to GND.
Feedback Input. For fixed output voltage devices, directly connect FB/VO to the output. For adjustable
output voltage devices, connect FB/VO to the center of the resistive divider between VOUT and GND.
Soft-Start Input. Connect a capacitor from SS to GND to set the soft-start time.
7
N.C./COMP
External Loop Compensation. For adjustable output voltage (MAX17501G/H) connect to an RC network
from COMP to GND. See the External Loop Compensation for Adjustable Output Versions section for
more details. For a fixed-output voltage (MAX17501A/B/E/F), this pin is a no connect (N.C.) and should
be left unconnected.
8
RESET
Open-Drain RESET Output. The RESET output is driven low if FB drops below 92.5% of its set value.
RESET goes high 1024 clock cycles after FB rises above 95.5% of its set value. RESET is valid when
the device is enabled and VIN is above 4.5V.
9
GND
10
LX
Switching Node. Connect LX to the switching side of the inductor. LX is high impedance when the device
is in shutdown mode.
—
EP
Exposed Pad. Connect to the GND pin of the IC. Connect to a large copper plane below the IC to improve
heat dissipation capability.
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Analog Ground
Maxim Integrated │ 11
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Block Diagram
VCC
PGND
N DRIVER
5µA
SS
LX
MAX17501
HICCUP
SS
P DRIVER
VIN
CURRENT
SENSE
VCC
PWM
COMPARATOR
LDO
CLK
PWM, PFM
LOGIC
OSC
COMP
HICCUP
SLOPE
COMPENSATION
START
EN
RESET
LOGIC
SS
900mV
REFERENCE
SWITCHOVER
LOGIC
RESET
COMP
N.C./COMP
GM
FB
INTERNAL
COMPENSATION
(FOR A, B, E, F VERSIONS)
GND
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Maxim Integrated │ 12
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Detailed Description
GND. The device employs an undervoltage-lockout circuit
that disables the internal linear regulator when VCC falls
below 3.7V (typical). The internal VCC linear regulator can
source up to 40mA (typical) to supply the device and to
power the low-side gate driver.
The device uses a peak-current-mode control scheme.
An internal transconductance error amplifier generates an
integrated error voltage. The error voltage sets the duty
cycle using a PWM comparator, a high-side current-sense
amplifier, and a slope-compensation generator. At each
rising edge of the clock, the high-side p-channel MOSFET
turns on and remains on until either the appropriate or
maximum duty cycle is reached, or the peak current limit
is detected.
Operating Input Voltage Range
The MAX17501 synchronous step-down regulator operates from 4.5V to 60V and delivers up to 500mA load
current. Output voltage regulation accuracy meets ±1.7%
over temperature.
During the high-side MOSFET’s on-time, the inductor
current ramps up. During the second half of the switching
cycle, the high-side MOSFET turns off and the low-side
n-channel MOSFET turns on and remains on until either
the next rising edge of the clock arrives or sink current
limit is detected. The inductor releases the stored energy
as its current ramps down, and provides current to the
output (the internal low RDSON pMOS/nMOS switches
ensure high efficiency at full load).
This device also integrates enable/undervoltage lockout
(EN/UVLO), adjustable soft-start time (SS), and opendrain reset output (RESET) functionality.
PFM Operation
The A and B versions of the MAX17501 feature a PFM
scheme to improve light load efficiency. At light loads,
once the part enters PFM mode, the inductor current is
forced to a fixed peak of 125mA (typical) every clock cycle
until the output rises to 103.3% of nominal voltage. Once
output reaches 103.3% of nominal voltage, both highside and low-side FETs are turned off and the part enters
hibernate operation until the load discharges output to
101.3% of nominal voltage. Most of the internal blocks
are turned off in hibernate operation to save quiescent
current. Such an operation reduces the effective switching frequency of the converter at light loads, resulting in
reduced switching losses and improved light load efficiency. The part naturally exits PFM mode when the load
current exceeds 62.5mA (typical).
Linear Regulator (VCC)
An internal linear regulator (VCC) provides a 5V nominal
supply to power the internal blocks and the low-side
MOSFET driver. The output of the VCC linear regulator
should be bypassed with a 1μF ceramic capacitor to
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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:
VIN(MIN) =
VOUT + (I OUT(MAX) × (R DCR + 0.47))
D MAX
+ (I OUT(MAX) × 0.73)
VIN(MAX) =
VOUT
f SW (MAX) × t ON(MIN)
where VOUT is the steady-state output voltage, IOUT(MAX)
is the maximum load current, RDCR is the DC resistance
of the inductor, fSW(MAX) is the switching frequency (maximum) and tON(MIN) is the worst-case minimum switch
on-time (120ns). The following table lists the fSW(MAX)
and DMAX values to be used for calculation for different
versions of the MAX17501:
PART VERSION
fSW (MAX) (kHz)
DMAX
MAX17501A/B/E/F/G
640
0.92
MAX17501H
320
0.965
Overcurrent Protection/HICCUP Mode
The device is provided with a robust overcurrent-protection scheme that protects the device under overload
and output short-circuit conditions. A cycle-by-cycle peak
current limit turns off the high-side MOSFET whenever
the high-side switch current exceeds an internal limit of
760mA (typ). A runaway current limit on the high-side
switch current at 780mA (typ) protects the device under
high input voltage, short-circuit conditions when there is
insufficient output voltage available to restore the inductor
current that built up during the on period of the step-down
converter. One occurrence of the runaway current limit
triggers a hiccup mode. In addition, if due to a fault condition, output voltage drops to 71.14% (typ) of its nominal
value any time after soft-start is complete, hiccup mode
is triggered.
Maxim Integrated │ 13
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
In hiccup mode, the converter is protected by suspending switching for a hiccup timeout period of 32,768 clock
cycles. Once the hiccup timeout period expires, soft-start
is attempted again. This operation results in minimal
power dissipation under overload fault conditions.
the input DC bus further. In applications where the source
is located distant from the device input, an electrolytic
capacitor should be added in parallel to the 1μF ceramic
capacitor to provide necessary damping for potential
oscillations caused by the longer input power path and
input ceramic capacitor.
The device includes a RESET comparator to monitor the
output voltage. The open-drain RESET output requires
an external pullup resistor. RESET can sink 2mA of current while low. RESET goes high (high impedance) 1024
switching cycles after the regulator output increases
above 95.5% of the designated nominal regulated voltage. RESET goes low when the regulator output voltage
drops to below 92.5% of the nominal regulated voltage.
RESET also goes low during thermal shutdown. RESET
is valid when the device is enabled and VIN is above 4.5V.
Inductor Selection
Prebiased Output
where VIN, VOUT, and fSW are nominal values. Ensure
that at any operating condition, the ratio (VOUT/(L x fSW))
is between 150mA and 250mA.
RESET Output
When the device starts into a prebiased output, both the
high-side and low-side switches are turned off so the
converter does not sink current from the output. Highside and low-side switches do not start switching until
the PWM comparator commands the first PWM pulse, at
which point switching commences first with the high-side
switch. The output voltage is then smoothly ramped up to
the target value in alignment with the internal reference.
Thermal-Overload Protection
Thermal-overload protection limits total power dissipa­tion
in the device. When the junction temperature of the device
exceeds +165°C, an on-chip thermal sensor shuts down
the device, allowing the device to cool. The thermal sensor
turns the device on again after the junc­tion temperature
cools by 10°C. Soft-start resets during thermal shutdown.
Carefully evaluate the total power dissipation (see the
Power Dissipation section) to avoid unwanted triggering of
the thermal-overload protection in normal operation.
Applications Information
Input Capacitor Selection
The discontinuous input-current waveform of the buck
converter causes large ripple currents in the input capacitor. The switching frequency, peak inductor cur­rent, and
the allowable peak-to-peak voltage ripple that reflects
back to the source dictate the capacitance requirement.
The device’s high switching frequency allows the use of
smaller value input capacitors. X7R capacitors are recommended in industrial applications for their temperature
stability. A minimum value of 1μF should be used for the
input capacitor. Higher values help reduce the ripple on
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Three key inductor parameters must be specified for
operation with the device: inductance value (L), inductor
saturation current (ISAT), and DC resistance (RDCR). The
switching frequency, input voltage, and output voltage
determine the inductor value as follows:
L=
VOUT × (VIN - VOUT )
0.15 × VIN × f SW
Select a low-loss inductor closest to the calculated value
with acceptable dimensions and having the lowest possible DC resistance. The saturation current rating (ISAT)
of the inductor must be high enough to ensure that saturation can occur only above the peak current-limit value
(IPEAK-LIMIT (typ) = 0.76A for the device).
Output Capacitor Selection
X7R ceramic output capacitors are preferred due to their
stability over temperature in industrial applications. The
output capacitor is usually sized to support a step load
of 50% of the maximum output current in the application,
so the output-voltage deviation is contained to ±3% of the
output-voltage change.
For fixed 3.3V and 5V output voltage versions, connect
a minimum of 10μF (1206) capacitor at the output. For
adjustable output voltage versions, the output capacitance can be calculated as follows:
C OUT=
1 I STEP × t RESPONSE
×
2
∆VOUT
t RESPONSE ≅
0.33
1
+
fC
f SW
where ISTEP is the load current step, tRESPONSE is the
response time of the controller, ΔVOUT is the allowable
output-voltage deviation, fC is the target closed-loop crossover frequency, and fSW is the switching frequency. Select
fC to be 1/12th of fSW. Consider DC bias and aging effects
while selecting the output capacitor.
Maxim Integrated │ 14
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Soft-Start Capacitor Selection
The MAX17501 implements adjustable soft-start operation to reduce inrush current. A capacitor con­nected from
the SS pin to GND programs the soft-start period.
The soft-start time (tSS) is related to the capacitor connected at SS (CSS) by the following equation:
C=
SS 5.55 × t SS
where tSS is in milliseconds and CSS is in nanofarads. For
example, to program a 600μs soft-start time, a 3300pF
capacitor should be connected from the SS pin to GND.
Ensure that (CSEL x VOUT/tSS) is less than 150mA,
where CSEL is the selected output capacitance.
Adjusting Output Voltage
The MAX17501A/E and MAX17501B/F have preset output voltages of 3.3V and 5.0V, respectively. Connect FB/
VO directly to the positive terminal of the output capacitor
(see the Typical Applications Circuits).
The MAX17501G/H offer an adjustable output voltage
from 0.9V to 92%VIN. Set the output voltage with a resistive voltage-divider connected from the positive terminal
of the output capacitor (VOUT) to GND (see Figure 1).
Connect the center node of the divider to FB/VO. To
optimize efficiency and output accuracy, use the following
procedure to choose the values of R4 and R5:
For MAX17501G, select the parallel combination of R4
and R5, Rp to be less than 15kΩ. For the MAX17501H,
select the parallel combination of R4 and R5, Rp to be
less than 30kΩ. Once Rp is selected, calculate R4 as:
R4 =
Calculate R5 as follows:
R5 =
Choose R1 to be 3.3MΩ, and then calculate R2 as:
R2 =
R1× 1.218
(VINU - 1.218)
where VINU is the voltage at which the device is required
to turn on. For adjustable output voltage devices, ensure
that VINU is higher than 0.8 x VOUT.
VIN
R1
FB/VO
R5
GND
Figure 1. Setting the Output Voltage
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R4 × 0.9
(VOUT - 0.9)
Setting the Input Undervoltage Lockout Level
The device offers an adjustable input undervoltagelockout level. Set the voltage at which the device turns
on with a resistive voltage-divider connected from VIN
to GND (see Figure 2). Connect the center node of the
divider to EN/UVLO.
VOUT
R4
Rp × VOUT
0.9
EN/UVLO
R2
GND
Figure 2. Adjustable EN/UVLO Network
Maxim Integrated │ 15
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
External Loop Compensation for Adjustable
Output Versions
The MAX17501 uses peak current-mode control scheme
and needs only a simple RC network to have a stable,
high-bandwidth control loop for the adjustable output voltage versions. The basic regulator loop is modeled as a
power modulator, an output feedback divider, and an error
amplifier. The power modulator has DC gain GMOD(dc),
with a pole and zero pair. The following equation defines
the power modulator DC gain:
1
G MOD(dc) =
1
0.2  0.5 - D 
+
+

R LOAD VIN  f SW × L SEL 
where RLOAD = VOUT/IOUT(MAX), fSW is the switching
frequency, LSEL is the selected output inductance, D is
the duty ratio, D = VOUT/VIN.
The compensation network is shown in Figure 3.
RZ can be calculated as:
R=
Z 12000 × f C × C SEL × VOUT
where RZ is in Ω. Choose fC to be 1/12th of the switching
frequency.
CZ can be calculated as follows:
CZ =
C SEL × G MOD(dc)
RZ
CP can be calculated as follows:
CP =
1
- 5pF
π × R Z × f SW
Power Dissipation
The exposed pad of the IC should be properly soldered to
the PCB to ensure good thermal contact. Ensure the junction
temperature of the device does not exceed +125°C under
the operating conditions specified for the power supply.
TO COMP PIN
RZ
CP
CZ
At high ambient temperatures, based on the operating
condition, the heat dissipated in the IC might exceed
the maximum junction temperature of +125°C. Heat sink
should be used to reduce θJA at such operating conditions. For typical applications, refer to the temperature
derating curves included in the MAX17501 Evaluation Kit
data sheet.
To prevent the part from exceeding 125°C junction temperature, users need to do some thermal analysis. At a
particular operating condition, the power losses that lead
to temperature rise of the device are estimated as follows:
(
1
PLOSS =
(POUT × ( - 1)) - I OUT 2 × R DCR
η
)
P=
OUT VOUT × I OUT
where POUT is the output power, η is is the efficiency of
the device, and RDCR is the DC resistance of the output
inductor (refer to the Typical Operating Characteristics
in the evaluation kit data sheets for more information on
efficiency at typical operating conditions).
The maximum power that can be dissipated in the 10-pin
TDFN-EP package is 1188.7mW at +70°C temperature.
The power dissipation capability should be derated as
the temperature goes above +70°C at 14.9mW/°C. For a
typical multilayer board, the thermal performance metrics
for the package are given as:
θ JA = 67.3°C W
θ JC = 18.2°C W
The junction temperature of the device can be estimated
at any given maximum ambient temperature (TA_MAX)
from the following equation:
TJ_MAX
= T A _MAX + (θ JA × PLOSS )
If the application has a thermal-management system that
ensures that the exposed pad of the device is maintained
at a given temperature (TEP_MAX) by using proper heat
sinks, then the junction temperature of the device can be
estimated at any given maximum ambient temperature as:
T=
J_MAX TEP_MAX + (θ JC × PLOSS )
Figure 3. External Compensation Network
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Maxim Integrated │ 16
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching losses and stable operation. For a sample layout that ensures
first-pass success, refer to the MAX17501 evaluation kit
layouts available at www.maximintegrated.com. Follow
these guidelines for good PCB layout:
1) All connections carrying pulsed currents must be very
short and as wide as possible. The loop area of these
connections must be made very small to reduce stray
inductance and radiated EMI.
PGND PLANE
2) A ceramic input filter capacitor should be placed close
to the VIN pin of the device. The bypass capacitor for
the VCC pin should also be placed close to the VCC
pin. External compensation components should be
placed close to the IC and far from the inductor. The
feedback trace should be routed as far as possible
from the inductor.
3) The analog small-signal ground and the power ground
for switch­
ing currents must be kept separate. They
should be connected together at a point where switching activity is at minimum, typically the return terminal
VOUT PLANE
C4
L1
C1
EP
VIN PLANE
LX PLANE
R1
R2
RESET
C2
R4
C3
GND PLANE
VIAS TO BOTTOM SIDE PGND PLANE
VIAS TO BOTTOM SIDE VOUT TRACK
VIAS TO BOTTOM SIDE GND PLANE
Figure 4. Recommended Component Placement for MAX17501A/B/E/F
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Maxim Integrated │ 17
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
PGND PLANE
VOUT PLANE
C4
L1
C1
LX PLANE
EP
VIN PLANE
R1
R2
RESET
R3
C2
R4
C3
R5
C9
C5
GND PLANE
VIAS TO BOTTOM SIDE PGND PLANE
VIAS TO BOTTOM SIDE VOUT TRACK
VIAS TO BOTTOM SIDE GND PLANE
Figure 5. Recommended Component Placement for MAX17501G/H
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Maxim Integrated │ 18
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Typical Applications Circuits
VIN
24V
C1
1µF
1206
LX
VIN
1
JU1 2
3
L1
33µH
C4
10µF,
1206
R1
3.32MΩ
EN/UVLO
R2
866kΩ
C2
1µF
C3
3300pF
PGND
VOUT
3.3V, 500mA
MAX17501
GND
VCC
FB/VO
SS
RESET
N.C.
RESET
Figure 6. MAX17501A/E Application Circuit (3.3V Output, 500mA Maximum Load Current, 600kHz Switching Frequency)
VIN
24V
C1
1µF
1206
LX
VIN
1
JU1 2
3
L1
47µH
C4
10µF,
1206
R1
3.32MΩ
EN/UVLO
R2
866kΩ
C2
1µF
C3
3300pF
PGND
VOUT
5V, 500mA
MAX17501
VCC
SS
N.C.
GND
FB/VO
RESET
RESET
Figure 7. MAX17501B/F Application Circuit (5V Output, 500mA Maximum Load Current, 600kHz Switching Frequency)
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Maxim Integrated │ 19
MAX17501
VIN
24V
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
C1
1µF
1206
LX
VIN
1
JU1 2
3
PGND
EN/UVLO
R2
316kΩ
C3
6800pF
VOUT
12V, 500mA
C4
4.7µF,
1206
R1
3.32MΩ
C2
1µF
R4
174kΩ
MAX17501
GND
VCC
FB/VO
SS
R5
14kΩ
COMP
C9
10pF
L1
100µH
RESET
RESET
R3
27.4kΩ
C5
1200pF
Figure 8. MAX17501G Application Circuit (12V Output, 500mA Maximum Load Current, 600kHz Switching Frequency)
VIN
24V
C1
2.2µF
1210
LX
VIN
1
JU1 2
3
C4
22µF,
1210
R1
3.32MΩ
EN/UVLO
R2
1MΩ
C2
1µF
C3
6800pF
PGND
VCC
SS
VOUT
2.5V, 500mA
R4
69.8kΩ
MAX17501
COMP
C9
47pF
L1
47µH
GND
FB/VO
R5
39.2kΩ
RESET
RESET
R3
20kΩ
C5
2200pF
Figure 9. MAX17501H Application Circuit (2.5V Output, 500mA Maximum Load Current, 300kHz Switching Frequency)
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Maxim Integrated │ 20
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Ordering Information/Selector Guide
PART
PIN-PACKAGE
OUTPUT VOLTAGE (V)
SWITCHING
FREQUENCY (kHz)
MODE
MAX17501AATB+
10 TDFN-EP*
3.3
600
PFM
MAX17501BATB+
10 TDFN-EP*
5
600
PFM
MAX17501EATB+
10 TDFN-EP*
3.3
600
PWM
MAX17501FATB+
10 TDFN-EP*
5
600
PWM
MAX17501GATB+
10 TDFN-EP*
Adjustable
600
PWM
MAX17501HATB+
10 TDFN-EP*
Adjustable
300
PWM
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Chip Information
PROCESS: BiCMOS
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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.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND PATTERN
NO.
10 TDFN
T1032N+1
21-0429
90-0082
Maxim Integrated │ 21
MAX17501
60V, 500mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converter
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
5/12
Initial release
1
11/12
Added MAX17501A, MAX17501B, MAX17501G, MAX17501H to data sheet
1–22
2
1/13
Added explanation on detailed condition for RESET
11, 14
3
7/13
4
8/14
Added output voltage accuracy for the MAX17501A and MAX17501B
Edited General Description, Benefits and Features, Pin Description, and
Adjusting Output Voltage sections
5
11/14
Removed automotive reference from Applications section
—
3
1, 11, 15
1
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.
© 2014 Maxim Integrated Products, Inc. │ 22
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