AVAILABLE
Functional Diagrams
Pin Configurations appear at end of data sheet.
Functional Diagrams continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
EVALUATION KIT AVAILABLE
General Description
The MAX5035 easy-to-use, high-efficiency, high-volt-
age, step-down DC-DC converter operates from an
input voltage up to 76V and consumes only 270µA qui-
escent current at no load. This pulse-width modulated
(PWM) converter operates at a fixed 125kHz switching
frequency at heavy loads, and automatically switches
to pulse-skipping mode to provide low quiescent cur-
rent and high efficiency at light loads. The MAX5035
includes internal frequency compensation simplifying
circuit implementation. The device uses an internal low-
on-resistance, high-voltage, DMOS transistor to obtain
high efficiency and reduce overall system cost. This
device includes undervoltage lockout, cycle-by-cycle
current limit, hiccup mode output short-circuit protec-
tion, and thermal shutdown.
The MAX5035 delivers up to 1A output current. The out-
put current may be limited by the maximum power dis-
sipation capability of the package. External shutdown is
included, featuring 10µA (typ) shutdown current. The
MAX5035A/B/C versions have fixed output voltages of
3.3V, 5V, and 12V, respectively, while the MAX5035D/E
versions have an adjustable output voltage from 1.25V
to 13.2V.
The MAX5035 is available in space-saving 8-pin SO
and 8-pin plastic DIP packages and operates over the
automotive (-40°C to +125°C) temperature range.
Applications
Automotive
Consumer Electronics
Industrial
Distributed Power
Features
oWide 7.5V to 76V Input Voltage Range
oFixed (3.3V, 5V, 12V) and Adjustable
(1.25V to 13.2V) Versions
o1A Output Current
oEfficiency Up to 94%
oInternal 0.4Ω High-Side DMOS FET
o270µA Quiescent Current at No Load, 10µA
Shutdown Current
oInternal Frequency Compensation
oFixed 125kHz Switching Frequency
oThermal Shutdown and Short-Circuit Current
Limit
o8-Pin SO and PDIP Packages
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Ordering Information
19-2988; Rev 5; 5/11
PART TEMP RANGE PIN-
PACKAGE
OU TPU T
VO LTA GE
( V)
MAX5035AUSA 0°C to +85°C 8 SO
MAX5035AUPA 0°C to +85°C 8 PDIP
MAX5035AASA -40°C to +125°C 8 SO
M AX 5035AAS A/V + -40°C to +125°C 8 SO
3.3
MAX5035BUSA 0°C to +85°C 8 SO
MAX5035BUPA 0°C to +85°C 8 PDIP
MAX5035BASA -40°C to +125°C 8 SO
M AX 5035BAS A/V + -40°C to +125°C 8 SO
5.0
1
2
3
4
BST
VD
SGND
FB
8
7
6
5
LX
TOP VIEW
VIN
GND
ON/OFF
MAX5035
SO/PDIP
Pin Configuration
MAX5035
GND
BST
LX
VIN
SGND
FB
D1
50SQ100
VD
100µHVOUT
5V
VIN
7.5V TO 76V
68µF
0.1µF
0.1µF
68µF
ON
OFF
R1
R2
ON/OFF
Typical Operating Circuit
/V denotes an automotive qualified part.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
Ordering Information continued at end of data sheet.
MAX5035
Ordering Information
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
ABSOLUTE MAXIMUM RATINGS
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.
(Voltages referenced to GND, unless otherwise specified.)
VIN .........................................................................-0.3V to +80V
SGND ....................................................................-0.3V to +0.3V
LX.................................................................-0.8V to (VIN + 0.3V)
BST ...............................................................-0.3V to (VIN + 10V)
BST (transient < 100ns)................................-0.3V to (VIN + 15V)
BST to LX................................................................-0.3V to +10V
BST to LX (transient < 100ns) ................................-0.3V to +15V
ON/OFF ..................................................................-0.3V to +80V
VD...........................................................................-0.3V to +12V
FB
MAX5035A/MAX5035B/MAX5035C ...................-0.3V to +15V
MAX5035D/E ......................................................-0.3V to +12V
VOUT Short-Circuit Duration (VIN ≤40V)........................Indefinite
VD Short-Circuit Duration ..............................................Indefinite
Continuous Power Dissipation (TA= +70°C)
8-Pin PDIP (derate 9.1mW/°C above +70°C)...............727mW
8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW
Operating Temperature Range
MAX5035_U_ _ ...................................................0°C to +85°C
MAX5035_A_ _ ..............................................-40°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Junction Temperature......................................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow)
Lead(Pb)-free...............................................................+260°C
Containing lead(Pb) .....................................................+240°C
ELECTRICAL CHARACTERISTICS (MAX5035_U_ _)
(VIN = +12V, VON/OFF = +12V, IOUT = 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical Application Circuit.
)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX5035A 7.5 76.0
MAX5035B 7.5 76.0
MAX5035C 15 76
Input Voltage Range VIN
MAX5035D/E 7.5 76.0
V
Undervoltage Lockout UVLO 5.2 V
MAX5035A VIN = 7.5V to 76V,
IOUT = 20mA to 1A 3.185 3.3 3.415
MAX5035B VIN = 7.5V to 76V,
IOUT = 20mA to 1A 4.85 5.0 5.15
Output Voltage VOUT
MAX5035C VIN = 15V to 76V,
IOUT = 20mA to 1A 11.64 12 12.36
V
VIN = 7.5V to 76V, MAX5035D/E 1.192 1.221 1.250
Feedback Voltage VFB VIN = 7.5V to 76V, MAX5035E 1.185 1.221 1.250 V
VIN = 12V, ILOAD = 0.5A, MAX5035A 86
VIN = 12V, ILOAD = 0.5A, MAX5035B 90
VIN = 24V, ILOAD = 0.5A, MAX5035C 94Efficiency η
VIN = 12V, VOUT = 5V, ILOAD = 0.5A,
MAX5035D/E 90
%
VFB = 3.5V, VIN = 7.5V to 76V, MAX5035A 270 440
VFB = 5.5V, VIN = 7.5V to 76V, MAX5035B 270 440
VFB = 13V, VIN = 15V to 76V, MAX5035C 270 440
VFB = 1.3V, MAX5035D 270 440
Quiescent Supply Current IQ
VFB = 1.3V, MAX5035E 340 460
µA
Shutdown Current ISHDN VON/OFF = 0V, VIN = 7.5V to 76V 10 45 µA
Peak Switch Current Limit ILIM (Note 1) 1.30 1.9 2.50 A
MAX5035
2
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued) (MAX5035_U_ _)
(VIN = +12V, VON/OFF = +12V, IOUT = 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical Application Circuit.
)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Switch Leakage Current IOL VIN = 76V, VON/OFF = 0V, VLX = 0V 0.01 1 µA
Switch On-Resistance RDS
ON
ISWITCH = 1A 0.40 0.80 Ω
PFM Threshold IPFM Minimum switch current in any cycle 55 85 130 mA
FB Input Bias Current IBMAX5035D/E -150 +0.01 +150 nA
ON/OFF CONTROL INPUT
Rising trip point for MAX5035A/B/C/D 1.53 1.69 1.85
ON/OFF Input-Voltage Threshold VON/OFF Rising trip point for MAX5035E 1.40 1.65 1.90 V
ON/OFF Input-Voltage Hysteresis VHYST 100 mV
ON/OFF Input Current ION/OFF VON/OFF = 0V to VIN 10 150 nA
ON/OFF Operating Voltage
Range VON/OFF 76 V
OSCILLATOR
Oscillator Frequency fOSC 109 125 135 kHz
Maximum Duty Cycle DMAX MAX5035D/E 95 %
VOLTAGE REGULATOR
Regulator Output Voltage VD VIN = 8.5V to 76V, IL = 0 6.9 7.8 8.8 V
Dropout Voltage 7.5V ≤ VIN ≤ 8.5V, IL = 1mA 2.0 V
Load Regulation ∆VD/∆IVD 0 to 5mA 150 Ω
PACKAGE THERMAL CHARACTERISTICS
SO package (JEDEC 51) 170
Thermal Resistance
(Junction to Ambient) θJA DIP package (JEDEC 51) 110 °C/W
THERMAL SHUTDOWN
Thermal-Shutdown Junction
Temperature TSH +160 °C
Thermal-Shutdown Hysteresis THYST 20 °C
ELECTRICAL CHARACTERISTICS (MAX5035_A_ _)
(VIN = +12V, VON/OFF = +12V, IOUT = 0, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C. See
the
Typical Application Circuit.
) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX5035A 7.5 76.0
MAX5035B 7.5 76.0
MAX5035C 15 76
Input Voltage Range VIN
MAX5035D/E 7.5 76.0
V
Undervoltage Lockout UVLO 5.2 V
MAX5035A VIN = 7.5V to 76V,
IOUT = 20mA to 1A 3.185 3.3 3.415
MAX5035B VIN = 7.5V to 76V,
IOUT = 20mA to 1A 4.825 5.0 5.175
Output Voltage VOUT
MAX5035C VIN = 15V to 76V,
IOUT = 20mA to 1A 11.58 12 12.42
V
MAX5035
Maxim Integrated
3
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
ELECTRICAL CHARACTERISTICS (MAX5035_A_ _) (continued)
(VIN = +12V, VON/OFF = +12V, IOUT = 0, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C. See
the
Typical Application Circuit.
) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
UNITS
VIN = 7.5V to 76V, MAX5035D
1.192 1.221 1.250
Feedback Voltage VFB VIN = 7.5V to 76V, MAX5035E
1.185 1.221 1.250
V
VIN = 12V, ILOAD = 0.5A, MAX5035A 86
VIN = 12V, ILOAD = 0.5A, MAX5035B 90
VIN = 24V, ILOAD = 0.5A, MAX5035C 94
Efficiency η
VIN = 12V, VOUT = 5V, ILOAD = 0.5A,
MAX5035D/E 90
%
VFB = 3.5V, VIN = 7.5V to 76V, MAX5035A
270
440
VFB = 5.5V, VIN = 7.5V to 76V, MAX5035B
270
440
VFB = 13V, VIN = 15V to 76V, MAX5035C
270
440
VFB = 1.3V, MAX5035D
270
440
Quiescent Supply Current IQ
VFB = 1.3V, MAX5035E
340
460
µA
Shutdown Current ISHDN VON/OFF = 0V, VIN = 7.5V to 76V 10 45 µA
Peak Switch Current Limit ILIM (Note 1)
1.30
1.9
2.50
A
VIN = 76V, VON/OFF = 0V, VLX = 0V 1
Switch Leakage Current IOL VIN = 76V, VON/OFF = 0V, VLX = 0V,
MAX5035E 5µA
Switch On-Resistance
RDS
ON
ISWITCH = 1A
0.40 0.80
Ω
PFM Threshold IPFM Minimum switch current in any cycle 55 85 130 mA
FB Input Bias Current IBMAX5035D/E
-150 +0.01 +150
nA
ON/OFF CONTROL INPUT
Rising trip point for MAX5035A/B/C/D
1.50 1.69 1.85
ON/OFF Input-Voltage Threshold VON/OFF
Rising trip point for MAX5035E
1.40 1.65 1.90
V
ON/OFF Input-Voltage Hysteresis
VHYST
100
mV
ON/OFF Input Current
ION/OFF
VON/OFF = 0V to VIN 10 150 nA
ON/OFF Operating Voltage
Range
VON/OFF
76 V
OSCILLATOR
Oscillator Frequency fOSC
105 125
137 kHz
Maximum Duty Cycle DMAX MAX5035D/E 95 %
VOLTAGE REGULATOR
Regulator Output Voltage VD VIN = 8.5V to 76V, IL = 0 6.5 7.8 9.0 V
Dropout Voltage 7.5V ≤ VIN ≤ 8.5V, IL = 1mA 2.0 V
Load Regulation
∆VD/∆IVD
0 to 5mA
150
Ω
MAX5035
4
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Typical Operating Characteristics
(VIN = 12V, VON/OFF = 12V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical
Application Circuit
, if applicable.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
PACKAGE THERMAL CHARACTERISTICS
SO package (JEDEC 51)
170
Thermal Resistance
(Junction to Ambient) θJA DIP package (JEDEC 51)
110
°C/W
THERMAL SHUTDOWN
Thermal-Shutdown Junction
Temperature TSH
+160
°C
Thermal-Shutdown Hysteresis THYST 20 °C
Note 1: Switch current at which current limit is activated.
Note 2: All limits at -40°C are guaranteed by design, not production tested.
VOUT vs. TEMPERATURE
(MAX5035AASA, VOUT = 3.3V)
MAX5035 toc01
TEMPERATURE (°C)
VOUT (V)
3.24
3.28
3.32
3.36
3.40
3.20
IOUT = 0.1A
IOUT = 1A
100
50
0-50 150-25 25 75 125
VOUT vs. TEMPERATURE
(MAX5035DASA, VOUT = 5V)
MAX5035 toc02
TEMPERATURE (°C)
VOUT (V)
125100-25 0 25 50 75
4.85
4.90
4.95
5.00
5.05
5.10
5.15
5.20
4.80
-50 150
IOUT = 0.1A
IOUT = 1A
LINE REGULATION
(MAX5035AASA, VOUT = 3.3V)
MAX5035 toc03
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
65503520
3.24
3.28
3.32
3.36
3.40
3.20
580
IOUT = 1A
IOUT = 0.1A
LINE REGULATION
(MAX5035DASA, VOUT = 5V)
MAX5035 toc04
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
655020 35
4.85
4.90
4.95
5.00
5.05
5.10
5.15
5.20
4.80
580
IOUT = 1A
IOUT = 0.1A
LOAD REGULATION
(MAX5035AASA, VOUT = 3.3V)
MAX5035 toc05
ILOAD (mA)
VOUT (V)
800600400200
3.24
3.28
3.32
3.36
3.40
3.20
0 1000
VIN = 7.5V, 24V
VIN = 76V
LOAD REGULATION
(MAX5035DASA, VOUT = 5V)
MAX5035 toc06
ILOAD (mA)
VOUT (V)
800600400200
4.95
5.00
5.05
5.10
4.90
01000
VIN = 76V
VIN = 24V
VIN = 7.5V
ELECTRICAL CHARACTERISTICS (MAX5035_A_ _) (continued)
(VIN = +12V, VON/OFF = +12V, IOUT = 0, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C. See
the
Typical Application Circuit.
) (Note 2)
MAX5035
Maxim Integrated
5
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 12V, VON/OFF = 12V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical
Application Circuit
, if applicable.)
OUTPUT CURRENT LIMIT
vs. TEMPERATURE
MAX5035 toc10
TEMPERATURE (°C)
OUTPUT CURRENT LIMIT (A)
1251007550250-25
0.5
1.0
1.5
2.0
0
-50 150
MAX5035DASA
VOUT = 5V
5% DROP IN VOUT
OUTPUT CURRENT LIMIT
vs. INPUT VOLTAGE
MAX5035 toc11
INPUT VOLTAGE (V)
OUTPUT CURRENT LIMIT (A)
65503520
0.8
1.1
1.4
1.7
2.0
0.5
580
MAX5035DASA
VOUT = 5V
5% DROP IN VOUT
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
MAX5035 toc12
TEMPERATURE (°C)
QUIESCENT SUPPLY CURRENT (µA)
230
260
290
320
350
200
100
50
0-50 150-25 25 75 125
QUIESCENT SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX5035 toc13
INPUT VOLTAGE (V)
QUIESCENT SUPPLY CURRENT (µA)
665646362616
230
260
290
320
350
200
676
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX5035 toc14
TEMPERATURE (°C)
SHUTDOWN CURRENT (µA)
5
10
15
20
25
0
100
50
0-50 150-25 25 75 125
SHUTDOWN CURRENT vs. INPUT VOLTAGE
MAX5035 toc15
INPUT VOLTAGE (V)
SHUTDOWN CURRENT (µA)
665646362616
4
8
12
16
20
0
676
EFFICIENCY vs. LOAD CURRENT
(MAX5035AASA, VOUT = 3.3V)
MAX5035 toc07
LOAD CURRENT (mA)
EFFICIENCY (%)
800600400200
10
20
30
40
50
60
70
80
90
100
0
0 1000
VIN = 76V
VIN = 48V
VIN = 24V
VIN = 12V
VIN = 7.5V
EFFICIENCY vs. LOAD CURRENT
(MAX5035DASA, VOUT = 5V)
MAX5035 toc08
LOAD CURRENT (mA)
EFFICIENCY (%)
800600400200
10
20
30
40
50
60
70
80
90
100
0
01000
VIN = 76V
VIN = 48V
VIN = 24V
VIN = 12V
VIN = 7.5V
EFFICIENCY vs. LOAD CURRENT
(MAX5035DASA, VOUT = 12V)
MAX5035 toc09
LOAD CURRENT (mA)
EFFICIENCY (%)
800600400200
10
20
30
40
50
60
70
80
90
100
0
0 1000
VIN = 76V
VIN = 48V
VIN = 24V
VIN = 15V
MAX5035
6
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 12V, VON/OFF = 12V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical
Application Circuit
, if applicable.)
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX5035 toc16
VIN (V)
VOUT (V)
12963
3
6
9
12
15
0
015
IOUT = 0
IOUT = 0.3A
IOUT = 1A
MAX5035DASA
VOUT = 12V
VON/OFF = VIN
MAX5035DASA
LOAD-TRANSIENT RESPONSE
MAX5035 toc17
400µs/div
B
A
A: VOUT, 200mV/div, AC-COUPLED
B: IOUT, 500mA/div, 0.1A TO 1A
VOUT = 5V
MAX5035DASA
LOAD-TRANSIENT RESPONSE
MAX5035 toc18
400µs/div
B
A
A: VOUT, 200mV/div, AC-COUPLED
B: IOUT, 500mA/div, 0.5A TO 1A
VOUT = 5V
MAX5035DASA
LOAD-TRANSIENT RESPONSE
MAX5035 toc19
400µs/div
B
A
A: VOUT, 200mV/div, AC-COUPLED
B: IOUT, 500mA/div, 0.1A TO 0.5A
VOUT = 5V
MAX5035DASA LX WAVEFORMS
MAX5035 toc20
4µs/div
B
0
A
0
A: SWITCH VOLTAGE (LX PIN), 20V/div (VIN = 48V)
B: INDUCTOR CURRENT, 500mA/div (IOUT = 1A)
MAX5035DASA LX WAVEFORMS
MAX5035 toc21
4µs/div
B
0
A
0
A: SWITCH VOLTAGE (LX PIN), 20V/div (VIN = 48V)
B: INDUCTOR CURRENT, 200mA/div (IOUT = 100mA)
MAX5035
Maxim Integrated
7
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN = 12V, VON/OFF = 12V, TA= -40°C to +125°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical
Application Circuit
, if applicable.)
MAX5035DASA LX WAVEFORMS
MAX5035 toc22
4µs/div
B
A
A: SWITCH VOLTAGE (LX PIN), 20V/div (VIN = 48V)
B: INDUCTOR CURRENT, 200mA/div (IOUT = 0)
0
0
MAX5035DASA STARTUP WAVEFORM
(IO = 0)
MAX5035 toc23
1ms/div
B
A
A: VON/OFF, 2V/div
B: VOUT, 2V/div
0
0
MAX5035DASA STARTUP WAVEFORM
(IO = 1A)
MAX5035 toc24
1ms/div
B
A
A: VON/OFF, 2V/div
B: VOUT, 2V/div
0
0
PEAK SWITCH CURRENT LIMIT
vs. INPUT VOLTAGE
MAX5035 toc25
INPUT VOLTAGE (V)
PEAK SWITCH CURRENT LIMIT (A)
56 6646362616
1.0
1.5
2.0
2.5
3.0
0.5
676
MAX5035DASA
VOUT = 5V
5% DROP IN VOUT
MAX5035
8
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Pin Description
PIN NAME FUNCTION
1 BST Boost Capacitor Connection. Connect a 0.1µF ceramic capacitor from BST to LX.
2 VD Internal Regulator Output. Bypass VD to GND with a 0.1µF ceramic capacitor.
3 SGND Internal Connection. SGND must be connected to GND.
4FB
Output Sense Feedback Connection. For fixed output voltage (MAX5035A, MAX5035B, MAX5035C),
connect FB to VOUT. For adjustable output voltage (MAX5035D, MAX5035E), use an external resistive
voltage-divider to set VOUT. VFB regulating set point is 1.22V.
5 ON/OFF Shutdown Control Input. Pull ON/OFF low to put the device in shutdown mode. Drive ON/OFF high for
normal operation.
6 GND Ground
7V
IN Input Voltage. Bypass VIN to GND with a low ESR capacitor as close to the device as possible.
8 LX Source Connection of Internal High-Side Switch
ENABLE
LX
BST
VIN
ON/OFF
VREF
REGULATOR
(FOR DRIVER)
REGULATOR
(FOR ANALOG)
OSC
RAMP
HIGH-SIDE
CURRENT
SENSE
IREF-PFM
IREF-LIM
CPFM
1.69V
CILIM
FB
x1
VREF EAMP
CONTROL
LOGIC
CPWM
VD
GND
Rh
Rl
CLK
SGND
MAX5035
TYPE 3
COMPENSATION THERMAL
SHUTDOWN
RAMP
Block Diagram
MAX5035
Maxim Integrated
9
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Detailed Description
The MAX5035 step-down DC-DC converter operates
from a 7.5V to 76V input voltage range. A unique volt-
age-mode control scheme with voltage feed-forward
and an internal switching DMOS FET provides high effi-
ciency over a wide input voltage range. This pulse-
width modulated converter operates at a fixed 125kHz
switching frequency. The device also features automat-
ic pulse-skipping mode to provide low quiescent cur-
rent and high efficiency at light loads. Under no load,
the MAX5035 consumes only 270µA, and in shutdown
mode, consumes only 10µA. The MAX5035 also fea-
tures undervoltage lockout, hiccup mode output short-
circuit protection, and thermal shutdown.
Shutdown Mode
Drive ON/OFF to ground to shut down the MAX5035.
Shutdown forces the internal power MOSFET off, turns
off all internal circuitry, and reduces the VIN supply cur-
rent to 10µA (typ). The ON/OFF rising threshold is
1.69V (typ). Before any operation begins, the voltage at
ON/OFF must exceed 1.69V (typ). The ON/OFF input
has 100mV hysteresis.
Undervoltage Lockout (UVLO)
Use the ON/OFF function to program the UVLO thresh-
old at the input. Connect a resistive voltage-divider
from VIN to GND with the center node to ON/OFF as
shown in Figure 1. Calculate the threshold value by
using the following formula:
The minimum recommended VUVLO(TH) is 6.5V, 7.5V, and
13V for the output voltages of 3.3V, 5V, and 12V, respec-
tively. The recommended value for R2 is less than 1MΩ.
If the external UVLO threshold-setting divider is not
used, an internal undervoltage-lockout feature monitors
the supply voltage at VIN and allows operation to start
when VIN rises above 5.2V (typ). This feature can be
used only when VIN rise time is faster than 2ms. For
slower VIN rise time, use the resistive-divider at
ON/OFF.
Boost High-Side Gate Drive (BST)
Connect a flying bootstrap capacitor between LX and
BST to provide the gate-drive voltage to the high-side
N-channel DMOS switch. The capacitor is alternately
charged from the internally regulated output voltage VD
and placed across the high-side DMOS driver. Use a
0.1µF, 16V ceramic capacitor located as close to the
device as possible.
On startup, an internal low-side switch connects LX to
ground and charges the BST capacitor to VD. Once the
BST capacitor is charged, the internal low-side switch
is turned off and the BST capacitor voltage provides
the necessary enhancement voltage to turn on the
high-side switch.
Thermal-Overload Protection
The MAX5035 features integrated thermal overload pro-
tection. Thermal overload protection limits total power
dissipation in the device, and protects the device in the
event of a fault condition. When the die temperature
exceeds +160°C, an internal thermal sensor signals the
shutdown logic, turning off the internal power MOSFET
and allowing the IC to cool. The thermal sensor turns the
internal power MOSFET back on after the IC’s die tem-
perature cools down to +140°C, resulting in a pulsed
output under continuous thermal overload conditions.
Applications Information
Setting the Output Voltage
The MAX5035A/B/C have preset output voltages of 3.3V,
5.0V, and 12V, respectively. Connect FB to the preset
output voltage (see the
Typical Operating Circuit
).
The MAX5035D/E versions offer an adjustable output
voltage. Set the output voltage with a resistive voltage-
divider connected from the circuit’s output to ground
(Figure 1). Connect the center node of the divider to
FB. Choose R4 less than 15kΩ, then calculate R3 as
follows:
RVR
OUT
3122
122 4=−×
(.)
.
VR
RV
UVLO TH() .=+
⎛
⎝
⎜⎞
⎠
⎟×11
2185
MAX5035D
GND
BST
LX
VIN
SGND
FB
D1
50SQ100
VD
100µH
VOUT
5V
VIN
7.5V TO 76V
68µF
0.1µF
0.1µF
COUT
68µF
R1
R2 R3
41.2kΩ
R4
13.3kΩ
ON/OFF
Figure 1. Adjustable Output Voltage
MAX5035
10
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
The MAX5035 features internal compensation for opti-
mum closed-loop bandwidth and phase margin. With
the preset compensation, it is strongly advised to sense
the output immediately after the primary LC.
Inductor Selection
The choice of an inductor is guided by the voltage dif-
ference between VIN and VOUT, the required output
current, and the operating frequency of the circuit. Use
an inductor with a minimum value given by:
where:
IOUTMAX is the maximum output current required, and
fSW is the operating frequency of 125kHz. Use an induc-
tor with a maximum saturation current rating equal to at
least the peak switch current limit (ILIM). Use inductors
with low DC resistance for higher efficiency.
Selecting a Rectifier
The MAX5035 requires an external Schottky rectifier as
a freewheeling diode. Connect this rectifier close to the
device using short leads and short PC board traces.
Choose a rectifier with a continuous current rating
greater than the highest expected output current. Use a
rectifier with a voltage rating greater than the maximum
expected input voltage, VIN. Use a low forward-voltage
Schottky rectifier for proper operation and high efficien-
cy. Avoid higher than necessary reverse-voltage
Schottky rectifiers that have higher forward-voltage
drops. Use a Schottky rectifier with forward-voltage
drop (VFB) less than 0.45V at +25°C and maximum load
current to avoid forward biasing of the internal body
diode (LX to ground). Internal body diode conduction
may cause excessive junction temperature rise and
thermal shutdown. Use Table 1 to choose the proper
rectifier at different input voltages and output current.
Input Bypass Capacitor
The discontinuous input-current waveform of the buck
converter causes large ripple currents in the input
capacitor. The switching frequency, peak inductor cur-
rent, and the allowable peak-to-peak voltage ripple that
reflects back to the source dictate the capacitance
requirement. The MAX5035 high switching frequency
allows the use of smaller-value input capacitors.
The input ripple is comprised of ∆VQ(caused by the
capacitor discharge) and ∆VESR (caused by the ESR of
the capacitor). Use low-ESR aluminum electrolytic
capacitors with high ripple-current capability at the input.
Assuming that the contribution from the ESR and capaci-
tor discharge is equal to 90% and 10%, respectively, cal-
culate the input capacitance and the ESR required for a
specified ripple using the following equations:
IOUT is the maximum output current of the converter
and fSW is the oscillator switching frequency (125kHz).
For example, at VIN = 48V, VOUT = 3.3V, the ESR and
input capacitance are calculated for the input peak-to-
peak ripple of 100mV or less yielding an ESR and
capacitance value of 80mΩand 51µF, respectively.
Low-ESR, ceramic, multilayer chip capacitors are recom-
mended for size-optimized application. For ceramic
capacitors, assume the contribution from ESR and capaci-
tor discharge is equal to 10% and 90%, respectively.
The input capacitor must handle the RMS ripple current
without significant rise in temperature. The maximum
capacitor RMS current occurs at about 50% duty cycle.
ESR V
II
IN ESR
OUT
=
+
∆
∆LL
IN OUT
CI
2
⎛
⎝
⎜⎞
⎠
⎟
=×DDD
Vf
where
QSW
()
:
1−
×∆
()
,∆IVV V
Vf L
LIN OUT OUT
IN SW
=−×
××
DV
V
OUT
IN
=
DV
V
OUT
IN
=
LVV D
If
IN OUT
OUTMAX SW
=−×
××
()
.03
VIN (V) DIODE PART NUMBER MANUFACTURER
15MQ040N IR
B240A Diodes, Inc.
B240 Central Semiconductor
7.5 to 36
MBRS240, MBRS1540 ON Semiconductor
30BQ060 IR
B360A Diodes, Inc.
CMSH3-60 Central Semiconductor
7.5 to 56
MBRD360, MBR3060 ON Semiconductor
50SQ100, 50SQ80 IR
7.5 to 76 MBRM5100 Diodes, Inc.
Table 1. Diode Selection
MAX5035
Maxim Integrated
11
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Ensure that the ripple specification of the input capaci-
tor exceeds the worst-case capacitor RMS ripple cur-
rent. Use the following equations to calculate the input
capacitor RMS current:
IPRMS is the input switch RMS current, IAVGIN is the
input average current, and ηis the converter efficiency.
The ESR of aluminum electrolytic capacitors increases
significantly at cold temperatures. Use a 1µF or greater
value ceramic capacitor in parallel with the aluminum
electrolytic input capacitor, especially for input voltages
below 8V.
Output Filter Capacitor
The worst-case peak-to-peak and RMS capacitor ripple
current, allowable peak-to-peak output ripple voltage,
and the maximum deviation of the output voltage dur-
ing load steps determine the capacitance and the ESR
requirements for the output capacitors.
The output capacitance and its ESR form a zero, which
improves the closed-loop stability of the buck regulator.
Choose the output capacitor so the ESR zero frequency
(fZ) occurs between 20kHz to 40kHz. Use the following
equation to verify the value of fZ. Capacitors with 100mΩ
to 250mΩESR are recommended to ensure the closed-
loop stability, while keeping the output ripple low.
The output ripple is comprised of ∆VOQ (caused by the
capacitor discharge) and ∆VOESR (caused by the ESR
of the capacitor). Use low-ESR tantalum or aluminum
electrolytic capacitors at the output. Assuming that the
contributions from the ESR and capacitor discharge
equal 80% and 20% respectively, calculate the output
capacitance and the ESR required for a specified rip-
ple using the following equations:
The MAX5035 has an internal soft-start time (tSS) of
400µs. It is important to keep the output rise time at
startup below tSS to avoid output overshoot. The output
rise time is directly proportional to the output capacitor.
Use 68µF or lower capacitance at the output to control
the overshoot below 5%.
In a dynamic load application, the allowable deviation
of the output voltage during the fast-transient load dic-
tates the output capacitance value and the ESR. The
output capacitors supply the step load current until the
controller responds with a greater duty cycle. The
response time (tRESPONSE) depends on the closed-
loop bandwidth of the converter. The resistive drop
across the capacitor ESR and capacitor discharge
cause a voltage droop during a step load. Use a com-
bination of low-ESR tantalum and ceramic capacitors
for better transient load and ripple/noise performance.
Keep the maximum output-voltage deviation above the
tolerable limits of the electronics being powered.
Assuming a 50% contribution each from the output
capacitance discharge and the ESR drop, use the fol-
lowing equations to calculate the required ESR and
capacitance value:
where ISTEP is the load step and tRESPONSE is the
response time of the controller. Controller response
time is approximately one-third of the reciprocal of the
closed-loop unity-gain bandwidth, 20kHz typically.
PCB Layout Considerations
Proper PCB layout is essential. Minimize ground noise
by connecting the anode of the Schottky rectifier, the
input bypass capacitor ground lead, and the output fil-
ter capacitor ground lead to a single point (“star”
CIt
V
OUT STEP RESPONSE
OQ
=×
∆
ESR V
I
OUT OESR
STEP
=∆
CI
Vf
OUT L
OQ SW
≈××
∆
∆22.
ESR V
I
OUT OESR
L
=∆
∆
fC ESR
ZOUT OUT
=×× ×
1
2π
IIIII
D
IV
PRMS PK DC PK DC
AVGIN
=++×
()
()
×
=
22
3
OOUT OUT
IN
PK OUT LDC OUT L
I
V
II III I
×
×
=+ =−
η
∆∆
22
,
andD V
V
OUT
IN
=
III
CRMS PRMS AVGIN
=−
2 22
where :
MAX5035
12
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
ground configuration). A ground plane is required.
Minimize lead lengths to reduce stray capacitance,
trace resistance, and radiated noise. In particular,
place the Schottky rectifier diode right next to the
device. Also, place BST and VD bypass capacitors
very close to the device. Use the PC board copper
plane connecting to VIN and LX for heatsinking.
MAX5035
GND
BST
LX
VIN
SGND
FB
D1
VD
L1
VOUT
VIN
CIN
0.1µF
0.1µF
COUT
R1
R2
ON/OFF
Figure 2. Fixed Output Voltages
VIN (V) VOUT (V) IOUT (A) EXTERNAL COMPONENTS
7.5 to 76 3.3 0.5
7.5 to 76 3.3 1
CIN = 68µF, Panasonic, EEVFK2A680Q
COUT = 68µF, Vishay Sprague, 594D686X_010C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 384kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 100µH, Coilcraft Inc., DO5022P-104
7.5 to 76 5 0.5
7.5 to 76 5 1
CIN = 68µF, Panasonic, EEVFK2A680Q
COUT = 68µF, Vishay Sprague, 594D68X_010C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 384kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 100µH, Coilcraft Inc., DO5022P-104
15 to 76 12 1
CIN = 68µF, Panasonic, EEVFK2A680Q
COUT = 15µF, Vishay Sprague, 594D156X0025C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 139kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 220µH, Coilcraft Inc., DO5022P-224
Table 2. Typical External Components Selection (Circuit of Figure 2)
Application Circuits
MAX5035
Maxim Integrated
13
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
VIN (V) VOUT (V) IOUT (A) EXTERNAL COMPONENTS
3.3 1
CIN = 220µF, Panasonic, EEVFK1E221P
COUT = 68µF, Vishay Sprague, 594D686X_010C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 274kΩ ±1%, 0805
D1 = B220, Diodes Inc.
L1 = 100µH, Coilcraft Inc., DO5022P-104
9 to 14
51
CIN = 220µF, Panasonic, EEVFK1E221P
COUT = 68µF, Vishay Sprague, 594D686X_010C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 274kΩ ±1%, 0805
D1 = B220, Diodes Inc.
L1 = 100µH, Coilcraft Inc., DO5022P-104
3.3 1
CIN = 220µF, Panasonic, EEVFK1H221P
COUT = 68µF, Vishay Sprague, 594D686X_010C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = MBRS2040, ON Semiconductor
L1 = 100µH, Coilcraft Inc., DO5022P-104
51
CIN = 220µF, Panasonic, EEVFK1H221P
COUT = 68µF, Vishay Sprague, 594D686X_010C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = MBRS2040, ON Semiconductor
L1 = 100µH, Coilcraft Inc., DO5022P-104
18 to 36
12 1
CIN = 220µF, Panasonic, EEVFK1H221P
COUT = 15µF, Vishay Sprague, 594D156X_0025C2T
CBST = 0.1µF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = MBRS2040, ON Semiconductor
L1 = 220µH, Coilcraft Inc., DO5022P-224
Table 2. Typical External Components Selection (Circuit of Figure 2) (continued)
MAX5035
14
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
SUPPLIER PHONE FAX WEBSITE
AVX Corporation 843-946-0238 843-626-3123 www.avxcorp.com
Coilcraft, Inc. 847-639-6400 847-639-1469 www.coilcraft.com
Diodes Incorporated 805-446-4800 805-446-4850 www.diodes.com
Panasonic Corp. 800-344-2112 714-737-7323 www.panasonic.com
SANYO Electric Co., Ltd. 619-661-6835 619-661-1055 www.sanyo.com
TDK Corp. 847-803-6100 847-390-4405 www.component.tdk.com
Vishay 402-563-6866 402-563-6296 www.vishay.com
Table 3. Component Suppliers
MAX5035
CIN
68µF
COUT
68µF
L1
100µH
FB
VOUT
5V AT 1A
BST
LX
SGND
0.1µF
0.1µF
GND
VIN
12V VIN
PTC*
Rt
Ct D1
B240
VD
*LOCATE PTC AS CLOSE TO HEAT-DISSIPATING COMPONENTS AS POSSIBLE.
ON/OFF
Figure 3. Load Temperature Monitoring with ON/OFF (Requires Accurate VIN)
MAX5035
Maxim Integrated
15
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
MAX5035B
CIN
68µF
COUT
68µF
L1
220µH
FB
VOUT
5V
BST
LX
SGND
0.1µF
0.1µF
GND
VIN
7.5V TO 36V VIN
R1
Rt
Ct D1
B240
VD
ON/OFF
MAX5035A
C'IN
68µF
C'OUT
68µF
L1'
100µH
FB
V'OUT
3.3V
BST
LX
SGND
0.1µF
0.1µF
GND
VIN
R1'
Rt'
Ct' D1'
B240
VD
ON/OFF
Figure 4. Dual-Sequenced DC-DC Converters (Startup Delay Determined by R1/R1’, Ct/Ct’ and Rt/Rt’)
Chip Information
PROCESS: BiCMOS
Ordering Information (continued)
PART TEMP RANGE PIN-
PACKAGE
OU TPU T
VO LTA GE
( V)
MAX5035CUSA 0°C to +85°C 8 SO
MAX5035CUPA 0°C to +85°C 8 PDIP
MAX5035CASA -40°C to +125°C 8 SO
M AX 5035C AS A/V + -40°C to +125°C 8 SO
12
MAX5035DUSA 0°C to +85°C 8 SO
MAX5035DUPA 0°C to +85°C 8 PDIP
MAX5035DASA -40°C to +125°C 8 SO
M AX 5035D AS A/V + -40°C to +125°C 8 SO
ADJ
MAX5035EUSA 0°C to +85°C 8 SO
MAX5035EASA -40°C to +125°C 8 SO
M AX 5035E AS A/V + -40°C to +125°C 8 SO
ADJ
/V denotes an automotive qualified part.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.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.
8 SO S8+2 21-0041 90-0096
8 PDIP P8+1 21-0043 —
MAX5035
16
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 9/03 Initial release —
1 6/04 Removed future-product asterisks and made specification changes 1, 2, 3
2 1/07 Modified Absolute Maximum Ratings section, updated Ordering Information, style edits 2, 3
3 5/09 Modified Absolute Maximum Ratings section 1, 2, 16, 18
4 4/10 Updated Electrical Characteristics table specifications 2, 3, 4, 16, 17
5 5/11 Added new variant (MAX5035E) 1–4, 9, 10, 16
Revision History
MAX5035
17
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
© 2011 Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.
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