EVALUATION KIT AVAILABLE
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
LE
AVAILAB
General Description
The MAX5035 easy-to-use, high-efficiency, high-voltage, step-down DC-DC converter operates from an
input voltage up to 76V and consumes only 270µA quiescent 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 current and high efficiency at light loads. The MAX5035
includes internal frequency compensation simplifying
circuit implementation. The device uses an internal lowon-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 protection, and thermal shutdown.
The MAX5035 delivers up to 1A output current. The output current may be limited by the maximum power dissipation 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.
Features
o Wide 7.5V to 76V Input Voltage Range
o Fixed (3.3V, 5V, 12V) and Adjustable
(1.25V to 13.2V) Versions
o 1A Output Current
o Efficiency Up to 94%
o Internal 0.4Ω High-Side DMOS FET
o 270µA Quiescent Current at No Load, 10µA
Shutdown Current
o Internal Frequency Compensation
o Fixed 125kHz Switching Frequency
o Thermal Shutdown and Short-Circuit Current
Limit
o 8-Pin SO and PDIP Packages
Ordering
Ordering Information
Information
PART
TEMP RANGE
MAX5035AUSA
MAX5035AUPA
MAX5035AASA
PINPACKAGE
0°C to +85°C
8 SO
0°C to +85°C
8 PDIP
OUTPUT
VOLTAGE
(V)
3.3
-40°C to +125°C 8 SO
MAX5035AASA/V+ -40°C to +125°C 8 SO
Applications
Functional Diagrams
Automotive
MAX5035BUSA
0°C to +85°C
8 SO
MAX5035BUPA
0°C to +85°C
8 PDIP
MAX5035BASA
Consumer Electronics
5.0
-40°C to +125°C 8 SO
MAX5035BASA/V+ -40°C to +125°C 8 SO
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
Ordering Information continued at end of data sheet.
Industrial
Distributed Power
Typical Operating Circuit
Pin Configuration
VIN
7.5V TO 76V
VIN
68µF
TOP VIEW
BST
0.1µF
100µH
MAX5035
LX
R1
D1
50SQ100
ON/OFF
68µF
ON
FB
R2
OFF
VD
SGND
VOUT
5V
GND
BST
1
8
LX
VD
2
7
VIN
SGND
3
6
GND
FB
4
5
ON/OFF
MAX5035
0.1µF
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.
SO/PDIP
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
19-2988; Rev 5; 5/11
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
ABSOLUTE MAXIMUM RATINGS
(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
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.
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
Input Voltage Range
Undervoltage Lockout
Output Voltage
Feedback Voltage
Efficiency
Quiescent Supply Current
Shutdown Current
Peak Switch Current Limit
2
SYMBOL
VIN
CONDITIONS
MIN
VFB
η
IQ
ISHDN
ILIM
MAX
7.5
76.0
MAX5035B
7.5
76.0
MAX5035C
15
76
MAX5035D/E
7.5
UVLO
VOUT
TYP
MAX5035A
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
MAX5035C
VIN = 15V to 76V,
IOUT = 20mA to 1A
11.64
12
12.36
VIN = 7.5V to 76V, MAX5035D/E
1.192
1.221
1.250
VIN = 7.5V to 76V, MAX5035E
1.185
1.221
1.250
VIN = 12V, ILOAD = 0.5A, MAX5035A
86
VIN = 12V, ILOAD = 0.5A, MAX5035B
90
94
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
VFB = 1.3V, MAX5035E
340
460
1.30
V
V
%
VIN = 24V, ILOAD = 0.5A, MAX5035C
VIN = 12V, VOUT = 5V, ILOAD = 0.5A,
MAX5035D/E
(Note 1)
V
76.0
5.2
VON/OFF = 0V, VIN = 7.5V to 76V
UNITS
µA
10
45
µA
1.9
2.50
A
Maxim Integrated
MAX5035
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
Switch Leakage Current
Switch On-Resistance
PFM Threshold
FB Input Bias Current
SYMBOL
IOL
RDS(ON)
IPFM
IB
TYP
MAX
UNITS
VIN = 76V, VON/OFF = 0V, VLX = 0V
CONDITIONS
0.01
1
µA
ISWITCH = 1A
0.40
0.80
Ω
Minimum switch current in any cycle
MIN
55
85
130
mA
MAX5035D/E
-150
+0.01
+150
nA
Rising trip point for MAX5035A/B/C/D
1.53
1.69
1.85
Rising trip point for MAX5035E
1.40
1.65
1.90
ON/OFF CONTROL INPUT
ON/OFF Input-Voltage Threshold
VON/OFF
ON/OFF Input-Voltage Hysteresis
VHYST
ON/OFF Input Current
ION/OFF
ON/OFF Operating Voltage
Range
VON/OFF
100
VON/OFF = 0V to VIN
10
V
mV
150
nA
76
V
135
kHz
OSCILLATOR
Oscillator Frequency
fOSC
Maximum Duty Cycle
DMAX
109
MAX5035D/E
125
95
%
VOLTAGE REGULATOR
Regulator Output Voltage
VD
Dropout Voltage
Load Regulation
∆VD/∆IVD
VIN = 8.5V to 76V, IL = 0
6.9
7.8
8.8
V
7.5V ≤ VIN ≤ 8.5V, IL = 1mA
2.0
V
0 to 5mA
150
Ω
SO package (JEDEC 51)
170
DIP package (JEDEC 51)
110
PACKAGE THERMAL CHARACTERISTICS
Thermal Resistance
(Junction to Ambient)
θJA
°C/W
THERMAL SHUTDOWN
Thermal-Shutdown Junction
Temperature
Thermal-Shutdown Hysteresis
TSH
+160
°C
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
Input Voltage Range
Undervoltage Lockout
Output Voltage
Maxim Integrated
SYMBOL
VIN
CONDITIONS
MIN
MAX
7.5
76.0
MAX5035B
7.5
76.0
MAX5035C
15
76
MAX5035D/E
7.5
76.0
UVLO
VOUT
TYP
MAX5035A
5.2
UNITS
V
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
MAX5035C
VIN = 15V to 76V,
IOUT = 20mA to 1A
11.58
12
12.42
V
3
MAX5035
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
Feedback Voltage
Efficiency
Quiescent Supply Current
Shutdown Current
Peak Switch Current Limit
SYMBOL
VFB
η
IQ
ISHDN
ILIM
CONDITIONS
MIN
TYP
MAX
VIN = 7.5V to 76V, MAX5035D
1.192
1.221
1.250
VIN = 7.5V to 76V, MAX5035E
1.185
1.221
1.250
VIN = 12V, ILOAD = 0.5A, MAX5035A
86
VIN = 12V, ILOAD = 0.5A, MAX5035B
90
VIN = 24V, ILOAD = 0.5A, MAX5035C
94
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
VFB = 1.3V, MAX5035E
340
460
VON/OFF = 0V, VIN = 7.5V to 76V
(Note 1)
1.30
VIN = 76V, VON/OFF = 0V, VLX = 0V
Switch Leakage Current
Switch On-Resistance
PFM Threshold
FB Input Bias Current
IOL
RDS(ON)
IPFM
IB
V
%
µA
10
45
µA
1.9
2.50
A
1
VIN = 76V, VON/OFF = 0V, VLX = 0V,
MAX5035E
5
ISWITCH = 1A
Minimum switch current in any cycle
UNITS
0.40
µA
0.80
Ω
55
85
130
mA
MAX5035D/E
-150
+0.01
+150
nA
Rising trip point for MAX5035A/B/C/D
1.50
1.69
1.85
Rising trip point for MAX5035E
1.40
1.65
1.90
ON/OFF CONTROL INPUT
ON/OFF Input-Voltage Threshold
VON/OFF
ON/OFF Input-Voltage Hysteresis
VHYST
ON/OFF Input Current
ION/OFF
ON/OFF Operating Voltage
Range
VON/OFF
100
VON/OFF = 0V to VIN
10
V
mV
150
nA
76
V
137
kHz
OSCILLATOR
Oscillator Frequency
fOSC
Maximum Duty Cycle
DMAX
105
MAX5035D/E
125
95
%
VOLTAGE REGULATOR
Regulator Output Voltage
VD
Dropout Voltage
Load Regulation
4
∆VD/∆IVD
VIN = 8.5V to 76V, IL = 0
6.5
7.8
9.0
V
7.5V ≤ VIN ≤ 8.5V, IL = 1mA
2.0
V
0 to 5mA
150
Ω
Maxim Integrated
MAX5035
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
PACKAGE THERMAL CHARACTERISTICS
Thermal Resistance
(Junction to Ambient)
θJA
SO package (JEDEC 51)
170
DIP package (JEDEC 51)
110
°C/W
THERMAL SHUTDOWN
Thermal-Shutdown Junction
Temperature
Thermal-Shutdown Hysteresis
TSH
+160
°C
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.
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.)
3.36
5.15
VOUT (V)
VOUT (V)
3.28
IOUT = 0.1A
5.05
5.00
4.95
IOUT = 0.1A
3.36
OUTPUT VOLTAGE (V)
5.10
IOUT = 1A
3.32
3.40
IOUT = 1A
4.90
3.24
MAX5035 toc03
IOUT = 0.1A
MAX5035 toc02
5.20
MAX5035 toc01
3.40
LINE REGULATION
(MAX5035AASA, VOUT = 3.3V)
VOUT vs. TEMPERATURE
(MAX5035DASA, VOUT = 5V)
VOUT vs. TEMPERATURE
(MAX5035AASA, VOUT = 3.3V)
IOUT = 1A
3.32
3.28
3.24
4.85
3.20
25
0
50
75
100 125 150
-50
-25
0
25
50
75
5
100 125 150
35
50
65
TEMPERATURE (°C)
INPUT VOLTAGE (V)
LINE REGULATION
(MAX5035DASA, VOUT = 5V)
LOAD REGULATION
(MAX5035AASA, VOUT = 3.3V)
LOAD REGULATION
(MAX5035DASA, VOUT = 5V)
3.36
5.05
VIN = 7.5V, 24V
5.00
3.28
IOUT = 1A
4.95
VIN = 24V
3.32
VOUT (V)
VOUT (V)
IOUT = 0.1A
80
MAX5035 toc06
VIN = 76V
5.10
5.10
MAX5035 toc05
3.40
MAX5035 toc04
5.15
5.05
20
TEMPERATURE (°C)
5.20
OUTPUT VOLTAGE (V)
3.20
4.80
-50 -25
VIN = 7.5V
5.00
VIN = 76V
4.90
4.95
3.24
4.85
3.20
4.80
5
20
35
50
INPUT VOLTAGE (V)
Maxim Integrated
65
80
4.90
0
200
400
600
ILOAD (mA)
800
1000
0
200
400
600
800
1000
ILOAD (mA)
5
MAX5035
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.)
VIN = 7.5V
50
VIN = 12V
40
VIN = 24V
200
400
600
800
VIN = 24V
MAX5035 toc09
VIN = 24V
50
VIN = 48V
40
VIN = 76V
20
VIN = 76V
10
0
0
200
400
600
800
200
0
1000
400
600
800
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
OUTPUT CURRENT LIMIT
vs. TEMPERATURE
OUTPUT CURRENT LIMIT
vs. INPUT VOLTAGE
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
1.1
MAX5035DASA
VOUT = 5V
5% DROP IN VOUT
0.5
-25
0
25
50
100 125 150
75
5
20
35
50
TEMPERATURE (°C)
INPUT VOLTAGE (V)
QUIESCENT SUPPLY CURRENT
vs. INPUT VOLTAGE
SHUTDOWN CURRENT
vs. TEMPERATURE
260
16
26
36
46
56
INPUT VOLTAGE (V)
66
76
230
-50 -25
25
0
100 125 150
75
50
SHUTDOWN CURRENT vs. INPUT VOLTAGE
15
10
20
16
12
8
4
0
200
260
TEMPERATURE (°C)
5
230
290
200
SHUTDOWN CURRENT (µA)
290
20
320
80
MAX5035 toc14
320
25
SHUTDOWN CURRENT (µA)
MAX5035 toc13
350
65
MAX5035 toc12
MAX5035 toc11
1.4
0.8
MAX5035DASA
VOUT = 5V
5% DROP IN VOUT
0
1.7
350
QUIESCENT SUPPLY CURRENT (µA)
0.5
2.0
OUTPUT CURRENT LIMIT (A)
MAX5035 toc10
1.0
6
VIN = 15V
60
LOAD CURRENT (mA)
1.5
-50
70
30
VIN = 48V
1000
2.0
OUTPUT CURRENT LIMIT (A)
VIN = 12V
40
80
0
0
QUIESCENT SUPPLY CURRENT (µA)
50
10
0
6
VIN = 7.5V
20
VIN = 76V
10
60
30
VIN = 48V
20
70
90
MAX5035 toc15
30
80
EFFICIENCY (%)
70
90
EFFICIENCY (%)
80
100
MAX5035 toc08
90
EFFICIENCY (%)
100
MAX5035 toc07
100
60
EFFICIENCY vs. LOAD CURRENT
(MAX5035DASA, VOUT = 12V)
EFFICIENCY vs. LOAD CURRENT
(MAX5035DASA, VOUT = 5V)
EFFICIENCY vs. LOAD CURRENT
(MAX5035AASA, VOUT = 3.3V)
0
-50 -25
0
25
50 75 100 125 150
TEMPERATURE (°C)
6
16
26
36
46
56
66
76
INPUT VOLTAGE (V)
Maxim Integrated
MAX5035
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
LOAD-TRANSIENT RESPONSE
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX5035DASA
LOAD-TRANSIENT RESPONSE
MAX5035 toc17
MAX5035 toc16
15
MAX5035DASA
VOUT = 12V
VON/OFF = VIN
12
MAX5035 toc18
VOUT = 5V
VOUT = 5V
A
VOUT (V)
A
9
6
IOUT = 1A
3
B
B
IOUT = 0.3A
IOUT = 0
0
0
3
6
9
12
15
VIN (V)
400µs/div
400µs/div
A: VOUT, 200mV/div, AC-COUPLED
B: IOUT, 500mA/div, 0.1A TO 1A
MAX5035DASA
LOAD-TRANSIENT RESPONSE
A: VOUT, 200mV/div, AC-COUPLED
B: IOUT, 500mA/div, 0.5A TO 1A
MAX5035DASA LX WAVEFORMS
MAX5035DASA LX WAVEFORMS
MAX5035 toc21
MAX5035 toc20
MAX5035 toc19
VOUT = 5V
A
A
A
0
0
B
B
B
0
0
400µs/div
A: VOUT, 200mV/div, AC-COUPLED
B: IOUT, 500mA/div, 0.1A TO 0.5A
Maxim Integrated
4µs/div
4µs/div
A: SWITCH VOLTAGE (LX PIN), 20V/div (VIN = 48V)
B: INDUCTOR CURRENT, 500mA/div (IOUT = 1A)
A: SWITCH VOLTAGE (LX PIN), 20V/div (VIN = 48V)
B: INDUCTOR CURRENT, 200mA/div (IOUT = 100mA)
7
MAX5035
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 STARTUP WAVEFORM
(IO = 0)
MAX5035DASA LX WAVEFORMS
MAX5035 toc23
MAX5035 toc22
A
A
0
0
B
B
0
0
1ms/div
4µs/div
A: VON/OFF, 2V/div
B: VOUT, 2V/div
A: SWITCH VOLTAGE (LX PIN), 20V/div (VIN = 48V)
B: INDUCTOR CURRENT, 200mA/div (IOUT = 0)
PEAK SWITCH CURRENT LIMIT
vs. INPUT VOLTAGE
MAX5035DASA STARTUP WAVEFORM
(IO = 1A)
MAX5035 toc24
A
0
B
MAX5035 toc25
PEAK SWITCH CURRENT LIMIT (A)
3.0
2.5
2.0
1.5
1.0
MAX5035DASA
VOUT = 5V
5% DROP IN VOUT
0
0.5
1ms/div
A: VON/OFF, 2V/div
B: VOUT, 2V/div
8
6
16
26
36
46
56
66
76
INPUT VOLTAGE (V)
Maxim Integrated
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Pin Description
PIN
NAME
1
BST
Boost Capacitor Connection. Connect a 0.1µF ceramic capacitor from BST to LX.
FUNCTION
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.
4
FB
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
7
VIN
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
Ground
Block Diagram
VIN
ON/OFF
ENABLE
REGULATOR
(FOR ANALOG)
1.69V
REGULATOR
(FOR DRIVER)
VD
CPFM
IREF-PFM
HIGH-SIDE
CURRENT
SENSE
CILIM
OSC
VREF
RAMP
IREF-LIM
BST
MAX5035
CLK
FB
RAMP
CONTROL
LOGIC
Rh
x1
Rl
TYPE 3
COMPENSATION
VREF
THERMAL
SHUTDOWN
CPWM
EAMP
GND
LX
SGND
Maxim Integrated
9
MAX5035
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 voltage-mode control scheme with voltage feed-forward
and an internal switching DMOS FET provides high efficiency over a wide input voltage range. This pulsewidth modulated converter operates at a fixed 125kHz
switching frequency. The device also features automatic pulse-skipping mode to provide low quiescent current and high efficiency at light loads. Under no load,
the MAX5035 consumes only 270µA, and in shutdown
mode, consumes only 10µA. The MAX5035 also features undervoltage lockout, hiccup mode output shortcircuit 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 current 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 threshold 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:
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 protection. 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 temperature 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 voltagedivider 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:
R1 ⎞
⎛
VUVLO(TH) = ⎜ 1 +
× 1. 85V
⎝
R2 ⎟⎠
The minimum recommended VUVLO(TH) is 6.5V, 7.5V, and
13V for the output voltages of 3.3V, 5V, and 12V, respectively. 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 V IN 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.
10
R3 =
(VOUT − 1. 22)
× R4
1. 22
VIN
7.5V TO 76V
68µF
R1
100µH
VIN
LX
0.1µF
ON/OFF
R2
VOUT
5V
D1
50SQ100
BST
COUT
68µF
R3
41.2kΩ
MAX5035D
FB
VD
SGND
GND
0.1µF
R4
13.3kΩ
Figure 1. Adjustable Output Voltage
Maxim Integrated
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
The MAX5035 features internal compensation for optimum 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 difference between VIN and VOUT, the required output
current, and the operating frequency of the circuit. Use
an inductor with a minimum value given by:
L =
(VIN − VOUT ) × D
0. 3 × IOUTMAX × fSW
where:
D=
VOUT
VIN
IOUTMAX is the maximum output current required, and
fSW is the operating frequency of 125kHz. Use an inductor 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.
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 current, 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 capacitor discharge is equal to 90% and 10%, respectively, calculate the input capacitance and the ESR required for a
specified ripple using the following equations:
∆ VESR
∆ IL ⎞
⎛
⎜⎝ IOUT + 2 ⎟⎠
I
× D (1− D)
C IN = OUT
∆ VQ × fSW
ESRIN =
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 efficiency. Avoid higher than necessary reverse-voltage
Schottky rectifiers that have higher forward-voltage
drops. Use a Schottky rectifier with forward-voltage
Table 1. Diode Selection
VIN (V)
DIODE PART NUMBER
15MQ040N
IR
B240A
Diodes, Inc.
B240
Central Semiconductor
MBRS240, MBRS1540
ON Semiconductor
7.5 to 36
7.5 to 56
7.5 to 76
MANUFACTURER
30BQ060
IR
B360A
Diodes, Inc.
CMSH3-60
Central Semiconductor
MBRD360, MBR3060
ON Semiconductor
50SQ100, 50SQ80
IR
MBRM5100
Diodes, Inc.
Maxim Integrated
where :
∆IL =
(VIN − VOUT ) × VOUT
,
VIN × fSW × L
D =
VOUT
VIN
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-topeak ripple of 100mV or less yielding an ESR and
capacitance value of 80mΩ and 51µF, respectively.
Low-ESR, ceramic, multilayer chip capacitors are recommended for size-optimized application. For ceramic
capacitors, assume the contribution from ESR and capacitor 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.
11
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Ensure that the ripple specification of the input capacitor exceeds the worst-case capacitor RMS ripple current. Use the following equations to calculate the input
capacitor RMS current:
capacitance and the ESR required for a specified ripple using the following equations:
ESR OUT =
I CRMS = IPRMS 2 − I AVGIN 2
where :
IPRMS =
(IPK 2 + IDC 2 + (IPK × IDC ) ) × D3
VO UT × IOUT
VIN × η
∆I
∆I
IPK = IOUT + L , IDC = IOUT − L
2
2
VOUT
and D =
VIN
I AVGIN =
IPRMS is the input switch RMS current, IAVGIN is the
input average current, and η is 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 during 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 250mΩ ESR are recommended to ensure the closedloop stability, while keeping the output ripple low.
fZ =
1
2 × π × C OUT × ESR OUT
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
12
C OUT ≈
∆ VOESR
∆ IL
∆ IL
2. 2 × ∆ VOQ × fSW
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 dictates 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 closedloop bandwidth of the converter. The resistive drop
across the capacitor ESR and capacitor discharge
cause a voltage droop during a step load. Use a combination 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 following equations to calculate the required ESR and
capacitance value:
ESR OUT =
∆ VOESR
I STEP
I
×t
C OUT = STEP RESPONSE
∆ VOQ
where I STEP is the load step and t RESPONSE 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 filter capacitor ground lead to a single point (“star”
Maxim Integrated
MAX5035
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.
Application Circuits
VIN
CIN
VIN
BST
0.1µF
L1
VOUT
LX
D1
R1
MAX5035
COUT
FB
ON/OFF
VD
R2
SGND
GND
0.1µF
Figure 2. Fixed Output Voltages
Table 2. Typical External Components Selection (Circuit of Figure 2)
VIN (V)
VOUT (V)
IOUT (A)
7.5 to 76
3.3
0.5
7.5 to 76
3.3
1
7.5 to 76
5
0.5
7.5 to 76
5
1
15 to 76
Maxim Integrated
12
1
EXTERNAL COMPONENTS
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
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
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
13
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Table 2. Typical External Components Selection (Circuit of Figure 2) (continued)
VIN (V)
VOUT (V)
3.3
IOUT (A)
EXTERNAL COMPONENTS
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
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
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
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
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
9 to 14
5
3.3
18 to 36
5
12
14
Maxim Integrated
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Table 3. Component Suppliers
PHONE
FAX
AVX Corporation
SUPPLIER
843-946-0238
843-626-3123
www.avxcorp.com
WEBSITE
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
MAX5035
PTC*
ON/OFF
VIN
12V
VIN
CIN
68µF
Ct
Rt
FB
BST
0.1µF
L1
100µH
VOUT
5V AT 1A
LX
VD
SGND GND
0.1µF
D1
B240
COUT
68µF
*LOCATE PTC AS CLOSE TO HEAT-DISSIPATING COMPONENTS AS POSSIBLE.
Figure 3. Load Temperature Monitoring with ON/OFF (Requires Accurate VIN)
Maxim Integrated
15
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
MAX5035B
R1
BST
ON/OFF
VIN
7.5V TO 36V
0.1µF
VIN
CIN
68µF
Ct
FB
VOUT
5V
LX
VD
Rt
L1
220µH
COUT
68µF
D1
B240
SGND GND
0.1µF
MAX5035A
R1'
ON/OFF
VIN
C'IN
68µF
Ct'
FB
BST
0.1µF
V'OUT
3.3V
LX
VD
Rt'
L1'
100µH
C'OUT
68µF
D1'
B240
SGND GND
0.1µF
Figure 4. Dual-Sequenced DC-DC Converters (Startup Delay Determined by R1/R1’, Ct/Ct’ and Rt/Rt’)
Ordering Information (continued)
PART
TEMP RANGE
PINPACKAGE
MAX5035CUSA
0°C to +85°C
8 SO
MAX5035CUPA
0°C to +85°C
8 PDIP
MAX5035CASA
-40°C to +125°C 8 SO
OUTPUT
VOLTAGE
(V)
0°C to +85°C
8 SO
MAX5035DUPA
0°C to +85°C
8 PDIP
MAX5035DASA
-40°C to +125°C 8 SO
12
ADJ
MAX5035DASA/V+ -40°C to +125°C 8 SO
MAX5035EUSA
MAX5035EASA
0°C to +85°C
8 SO
-40°C to +125°C 8 SO
PROCESS: BiCMOS
Package Information
MAX5035CASA/V+ -40°C to +125°C 8 SO
MAX5035DUSA
Chip 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
—
ADJ
MAX5035EASA/V+ -40°C to +125°C 8 SO
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
16
Maxim Integrated
MAX5035
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Revision History
REVISION
NUMBER
REVISION
DATE
0
9/03
Initial release
1
6/04
Removed future-product asterisks and made specification changes
2
1/07
Modified Absolute Maximum Ratings section, updated Ordering Information, style edits
3
5/09
Modified Absolute Maximum Ratings section
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
DESCRIPTION
PAGES
CHANGED
—
1, 2, 3
2, 3
1, 2, 16, 18
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© Maxim Integrated
17
The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.
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