General Description
The MAX5033 easy-to-use, high-efficiency, high-voltage,
step-down DC-DC converter operates from an input volt-
age up to 76V and consumes only 270μA quiescent cur-
rent at no load. This pulse-width modulated (PWM)
converter operates at a fixed 125kHz switching frequen-
cy at heavy loads, and automatically switches to pulse-
skipping mode to provide low quiescent current and
high efficiency at light loads. The MAX5033 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 protection, and
thermal shutdown.
The MAX5033 delivers up to 500mA 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 MAX5033A/B/C versions have fixed output
voltages of 3.3V, 5V, and 12V, respectively, while the
MAX5033D features an adjustable output voltage, from
1.25V to 13.2V.
The MAX5033 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
♦Wide 7.5V to 76V Input Voltage Range
♦Fixed (3.3V, 5V, 12V) and Adjustable (1.25V to
13.2V) Voltage Versions
♦500mA Output Current
♦Efficiency Up to 94%
♦Internal 0.4Ω High-Side DMOS FET
♦270µA Quiescent Current at No Load, 10µA
Shutdown Current
♦Internal Frequency Compensation
♦Fixed 125kHz Switching Frequency
♦Thermal Shutdown and Short-Circuit Current Limit
♦8-Pin SO and PDIP Packages
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-2979; Rev 4; 4/10
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PART TEMP RANGE PIN-
PACKAGE
OUTPUT
VOLTAGE
(V)
MAX5033AUSA 0°C to +85°C 8 SO
MAX5033AUPA 0°C to +85°C 8 PDIP
MAX5033AASA -40°C to +125°C 8 SO
3.3
MAX5033BUSA 0°C to +85°C 8 SO
MAX5033BUPA 0°C to +85°C 8 PDIP
MAX5033BASA -40°C to +125°C 8 SO
5.0
MAX5033CUSA 0°C to +85°C 8 SO
MAX5033CUPA 0°C to +85°C 8 PDIP
MAX5033CASA -40°C to +125°C 8 SO
12
MAX5033DUSA 0°C to +85°C 8 SO
MAX5033DUPA 0°C to +85°C 8 PDIP
MAX5033DASA -40°C to +125°C 8 SO
ADJ
1
2
3
4
BST
VD
SGND
FB
8
7
6
5
LX
VIN
GND
ON/OFF
MAX5033
SO/PDIP
Pin Configuration
MAX5033
GND
BST
LX
VIN
SGND
FB
D1
50SQ100
VD
220μHVOUT
5V, 0.5A
VIN
7.5V TO 76V
47μF
0.1μF
0.1μF
33μF
ON
OFF
R1
R2
ON/OFF
Typical Operating Circuit
This product is available in both leaded(Pb) and lead(Pb)-free
packages. To order the lead(Pb)-free package, add a + after
the part number.
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
2 _______________________________________________________________________________________
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
MAX5033A/MAX5033B/MAX5033C ...................-0.3V to +15V
MAX5033D .........................................................-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
MAX5033_U_ _ ...................................................0°C to +85°C
MAX5033_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)
SO, PDIP Lead(Pb)-free...............................................+260°C
SO, PDIP Containing lead(Pb) .....................................+240°C
ELECTRICAL CHARACTERISTICS (MAX5033_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
MAX5033A 7.5 76.0
MAX5033B 7.5 76.0
MAX5033C 15 76
Input Voltage Range VIN
MAX5033D 7.5 76.0
V
Undervoltage Lockout UVLO 5.2 V
MAX5033A, VIN = 7.5V to 76V,
IOUT = 20mA to 500mA 3.185 3.3 3.415
MAX5033B, VIN = 7.5V to 76V,
IOUT = 20mA to 500mA 4.85 5.0 5.15
Output Voltage VOUT
MAX5033C, VIN = 15V to 76V,
IOUT = 20mA to 500mA 11.64 12 12.36
V
Feedback Voltage VFB VIN = 7.5V to 76V, MAX5033D 1.192 1.221 1.250 V
VIN = 12V, ILOAD = 500mA, MAX5033A 86
VIN = 12V, ILOAD = 500mA, MAX5033B 90
VIN = 24V, ILOAD = 500mA, MAX5033C 94Efficiency η
VIN = 12V, VOUT = 5V, ILOAD = 500mA,
MAX5033D 90
%
VFB = 3.5V, VIN = 7.5V to 76V, MAX5033A 270 440
VFB = 5.5V, VIN = 7.5V to 76V, MAX5033B 270 440
VFB = 13V, VIN = 15V to 76V, MAX5033C 270 440
Quiescent Supply Current IQ
VFB = 1.3V, MAX5033D 270 440
μA
Shutdown Current ISHDN VON/OFF = 0V, VIN = 7.5V to 76V 10 45 μA
Peak Switch Current Limit ILIM (Note 1) 0.95 1.5 2.1 A
Switch Leakage Current IOL VIN = 76V, VON/OFF = 0V, VLX = 0V 1 μA
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (MAX5033_U_ _) (continued)
(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 On-Resistance RDS
(
ON
)
ISWITCH = 500mA 0.4 0.80 Ω
PFM Threshold IPFM Minimum switch current in any cycle 35 65 95 mA
FB Input Bias Current IBMAX5033D -150 +0.01 +150 nA
ON/OFF CONTROL INPUT
ON/OFF Input-Voltage Threshold VON/OFF Rising trip point 1.53 1.69 1.85 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 O p er ati ng V ol tag e Rang eV
ON/OFF 76 V
OSCILLATOR
Oscillator Frequency fOSC 109 125 135 kHz
Maximum Duty Cycle DMAX MAX5033D 95 %
VOLTAGE REGULATOR
Regulator Output Voltage VD VIN = 8.5V to 76V, IL = 0mA 6.9 7.8 8.8 V
Dropout Voltage 7.5V ≤ VIN ≤ 8.5V, IL = 1mA 2.0 V
Load Regulation ΔVD/ΔIVD 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 (MAX5033_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
MAX5033A 7.5 76.0
MAX5033B 7.5 76.0
MAX5033C 15 76
Input Voltage Range VIN
MAX5033D 7.5 76.0
V
Undervoltage Lockout UVLO 5.2 V
MAX5033A, VIN = 7.5V to 76V,
IOUT = 20mA to 500mA 3.185 3.3 3.415
MAX5033B, VIN = 7.5V to 76V,
IOUT = 20mA to 500mA 4.825 5.0 5.175
Output Voltage VOUT
MAX5033C, VIN = 15V to 76V,
IOUT = 20mA to 500mA 11.58 12 12.42
V
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (MAX5033_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
Feedback Voltage VFB VIN = 7.5V to 76V, MAX5033D 1.192 1.221 1.250 V
VIN = 12V, ILOAD = 500mA, MAX5033A 86
VIN = 12V, ILOAD = 500mA, MAX5033B 90
VIN = 24V, ILOAD = 500mA, MAX5033C 94Efficiency η
VIN = 12V, VOUT = 5V, ILOAD = 500mA,
MAX5033D 90
%
VFB = 3.5V, VIN = 7.5V to 76V, MAX5033A 270 440
VFB = 5.5V, VIN = 7.5V to 76V, MAX5033B 270 440
VFB = 13V, VIN = 15V to 76V, MAX5033C 270 440
Quiescent Supply Current IQ
VFB = 1.3V, MAX5033D 270 440
μA
Shutdown Current ISHDN VON/OFF = 0V, VIN = 7.5V to 76V 10 45 μA
Peak Switch Current Limit ILIM (Note 1) 0.95 1.5 2.20 A
Switch Leakage Current IOL VIN = 76V, VON/OFF = 0V, VLX = 0V 1 μA
Switch On-Resistance RDS
(
ON
)
ISWITCH = 500mA 0.4 0.80 Ω
PFM Threshold IPFM Minimum switch current in any cycle 35 65 110 mA
FB Input Bias Current IBMAX5033D -150 +0.01 +150 nA
ON/OFF CONTROL INPUT
ON/OFF Input-Voltage Threshold VON/OFF Rising trip point 1.50 1.69 1.85 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 O p er ati ng V ol tag e Rang eV
ON/OFF 76 V
OSCILLATOR
Oscillator Frequency fOSC 105 125 137 kHz
Maximum Duty Cycle DMAX MAX5033D 95 %
VOLTAGE REGULATOR
Regulator Output Voltage VD VIN = 8.5V to 76V, IL = 0mA 6.5 7.8 9.0 V
Dropout Voltage 7.5V ≤ VIN ≤ 8.5V, IL = 1mA 2.0 V
Load Regulation ΔVD/ΔIVD 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
Note 1: Switch current at which the current limit is activated.
Note 2: All limits at -40°C are guaranteed by design, not production tested.
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
_______________________________________________________________________________________
5
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.)
VOUT vs. TEMPERATURE
(MAX5033CASA, VOUT = 12V)
MAX5033 toc01
TEMPERATURE (°C)
VOUT (V)
11.9
12.0
12.1
12.2
12.3
12.4
11.8
100
50
0
-50 150
-25 25 75 125
IOUT = 0.1A
IOUT = 0.5A
VOUT vs. TEMPERATURE
(MAX5033BASA, VOUT = 5V)
MAX5033 toc02
TEMPERATURE (°C)
VOUT (V)
4.95
5.00
5.05
5.10
4.90
IOUT = 0.1A
IOUT = 0.5A
100
500
-50 150
-25 25 75 125
LINE REGULATION
(MAX5033CASA, VOUT = 12V)
MAX5033 toc03
INPUT VOLTAGE (V)
VOUT (V)
50 60 70403020
11.9
12.0
12.1
12.2
12.3
12.4
11.8
10 80
IOUT = 0A
IOUT = 0.5A
LINE REGULATION
(MAX5033BASA, VOUT = 5V)
MAX5033 toc04
INPUT VOLTAGE (V)
VOUT (V)
46 56 66362616
4.95
5.00
5.05
5.10
4.90
676
IOUT = 0A
IOUT = 0.5A
LOAD REGULATION
(MAX5033CASA, VOUT = 12V)
MAX5033 toc05
ILOAD (mA)
VOUT (V)
400300200100
11.9
12.0
12.1
12.2
12.3
12.4
11.8
0 500
VIN = 24V
VIN = 76V
LOAD REGULATION
(MAX5033BASA, VOUT = 5V)
MAX5033 toc06
ILOAD (mA)
VOUT (V)
400300200100
4.95
5.00
5.05
5.10
4.90
0 500
VIN = 7.5V, 24V
VIN = 76V
EFFICIENCY vs. LOAD CURRENT
(MAX5033BASA, VOUT = 5V)
MAX5033 toc07
LOAD CURRENT (mA)
EFFICIENCY (%)
400300200100
30
50
40
20
10
70
60
100
90
80
0
0 500
VIN = 7.5V
VIN = 12V
VIN = 24V
VIN = 48V
VIN = 76V
EFFICIENCY vs. LOAD CURRENT
(MAX5033CASA, VOUT = 12V)
MAX5033 toc08
LOAD CURRENT (mA)
EFFICIENCY (%)
400300200100
30
50
40
20
10
70
60
100
90
80
0
0 500
VIN = 15V
VIN = 24V
VIN = 48V
VIN = 76V
OUTPUT CURRENT LIMIT
vs. TEMPERATURE
MAX5033 toc09
TEMPERATURE (°C)
OUTPUT CURRENT LIMIT (A)
0.8
1.1
1.4
1.7
2.0
0.5
MAX5033BASA
5% DROP IN VOUT
100
50
0-50 150
-25 25 75 125
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
6 _______________________________________________________________________________________
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. INPUT VOLTAGE
MAX5033 toc10
INPUT VOLTAGE (V)
OUTPUT CURRENT LIMIT (A)
665646362616
0.8
1.1
1.4
1.7
2.0
0.5
676
MAX5033BASA
VOUT = 5V
5% DROP IN VOUT
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
MAX5033 toc11
TEMPERATURE (°C)
QUIESCENT SUPPLY CURRENT (μA)
240
280
320
360
400
200
100
50
0-50 150
-25 25 75 125
QUIESCENT SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX5033 toc12
INPUT VOLTAGE (V)
QUIESCENT SUPPLY CURRENT (μA)
230
260
290
320
350
200
66
46
266 16 36 56 76
SHUTDOWN CURRENT
vs. TEMPERATURE
MAX5033 toc13
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
MAX5033 toc14
INPUT VOLTAGE (V)
SHUTDOWN CURRENT (μA)
5
10
15
20
25
0
66
46
266 16 36 56 76
OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX5033 toc15
VIN (V)
VOUT (V)
12963
3
6
9
12
15
0
015
MAX5033CASA
VOUT = 12V
VON/OFF = VIN
IOUT = 0.3A
IOUT = 0.5A
MAX5033BASA
LOAD-TRANSIENT RESPONSE
MAX5033 toc16
400μs/div
B
A
A: VOUT, 200mV/div, AC-COUPLED
B: IOUT, 500mA/div, 100mA TO 500mA
VOUT = 5V
MAX5033BASA
LOAD-TRANSIENT RESPONSE
MAX5033 toc17
400μs/div
B
A
A: VOUT, 100mV/div, AC-COUPLED
B: IOUT, 200mA/div, 100mA TO 250mA
VOUT = 5V
MAX5033BASA
LOAD-TRANSIENT RESPONSE
MAX5033 toc18
400μs/div
B
A
A: VOUT, 100mV/div, AC-COUPLED
B: IOUT, 500mA/div, 250mA TO 500mA
VOUT = 5V
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
_______________________________________________________________________________________
7
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.)
MAX5033BASA
LX WAVEFORMS
MAX5033 toc19
4μs/div
B
0
A
A: SWITCH VOLTAGE (LX PIN) 20V/div, VIN = 48V
B: INDUCTOR CURRENT, 200mA/div, (IOUT = 500mA)
MAX5033BASA LX WAVEFORMS
MAX5033 toc20
4μs/div
B
0
A
0
A: SWITCH VOLTAGE, 20V/div, VIN = 48V
B: INDUCTOR CURRENT, 100mA/div (IOUT = 30mA)
MAX5033BASA LX WAVEFORMS
MAX5033 toc21
4μs/div
B
A
A: SWITCH VOLTAGE (LX PIN), 20V/div, VIN = 48V
B: INDUCTOR CURRENT, 100mA/div (IOUT = 0)
0
0
MAX5033BASA STARTUP WAVEFORM
(IO = 0)
MAX5033 toc22
1ms/div
B
A
A: VON/OFF, 2V/div
B: VOUT, 2V/div
PEAK SWITCH CURRENT LIMIT
vs. INPUT VOLTAGE
MAX5033 toc24
INPUT VOLTAGE (V)
PEAK SWITCH CURRENT LIMIT (A)
56 6646362616
0.8
1.1
1.4
1.7
2.0
0.5
676
MAX5033BASA
VOUT = 5V
5% DROP IN VOUT
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
8 _______________________________________________________________________________________
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 (MAX5033A, MAX5033B, MAX5033C),
connect FB to VOUT. For adjustable output voltage (MAX5033D), 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
MAX5033
TYPE 3
COMPENSATION THERMAL
SHUTDOWN
RAMP
Simplified Block Diagram
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
_______________________________________________________________________________________ 9
Detailed Description
The MAX5033 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 MAX5033 consumes only 270μA, and in shutdown
mode, consumes only 10μA. The MAX5033 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 MAX5033.
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,
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 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 MAX5033 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 sen-
sor signals the shutdown logic, turning off the internal
power MOSFET and allowing the IC to cool. The ther-
mal 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 MAX5033A/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 MAX5033D offers an adjustable output voltage. Set
the output voltage with a resistive voltage-divider con-
nected 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
MAX5033D
GND
BST
LX
VIN
SGND
FB
D1
50SQ100
VD
220μH
VOUT
5V, 0.5A
VIN
7.5V TO 76V
47μF
0.1μF
0.1μF
COUT
33μF
R1
R2 R3
41.2kΩ
R4
13.3kΩ
ON/OFF
Figure 1. Adjustable Output Voltage
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
10 ______________________________________________________________________________________
The MAX5033 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: 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.
Selecting a Rectifier
The MAX5033 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 con-
duction 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 MAX5033 high switching frequency
allows the use of smaller-value input capacitors.
The input ripple is comprised of ΔVQ(caused by the
capacitor discharge) and ΔVESR (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 and 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 130mΩand 27μF, respectively.
Low-ESR, ceramic, multilayer chip capacitors are recom-
mended for size-optimized application. For ceramic
capacitors, assume the contribution from ESR and capac-
itor 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
=
+
Δ
ΔLL
IN OUT
CI
2
⎛
⎝
⎜⎞
⎠
⎟
=×DDD
Vf
where
QSW
()
:
1−
×Δ
()
ΔIVV V
Vf L
LIN OUT OUT
IN SW
=−×
××
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
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
______________________________________________________________________________________ 11
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 ΔVOQ (caused by the
capacitor discharge) and ΔVOESR (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 MAX5033 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 from the output capaci-
tance discharge and the ESR drop, use the following
equations to calculate the required ESR and capaci-
tance 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 (typ).
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
=×
Δ
ESR V
I
OUT OESR
STEP
=Δ
CI
Vf
OUT L
OQ SW
≈××
Δ
Δ22.
ESR V
I
OUT OESR
L
=Δ
Δ
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
ΔΔ
22
,
andD V
V
OUT
IN
=
III
CRMS PRMS AVGIN
=−
2 22
where :
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
12 ______________________________________________________________________________________
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 PCB copper plane
connecting to VIN and LX for heatsinking.
MAX5033
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
CIN = 47μF, Panasonic, EEVFK2A470Q
COUT = 47μF, Vishay Sprague, 594D476X_016C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 384kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 150μH, Coilcraft Inc., DO5022P-154
7.5 to 76 5 0.5
CIN = 47μF, Panasonic, EEVFK2A470Q
COUT = 33μF, Vishay Sprague, 594D336X_016C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 384kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 220μH, Coilcraft Inc., DO5022P-224
15 to 76 12 0.5
CIN = 47μF, Panasonic, EEVFK2A470Q
COUT = 15μF, Vishay Sprague, 594D156X_025C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 384kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 330μH, Coilcraft Inc., DO5022P-334
Table 2. Typical External Components Selection (Circuit of Figure 2)
Application Circuits
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
______________________________________________________________________________________ 13
VIN (V) VOUT (V) IOUT (A) EXTERNAL COMPONENTS
3.3 0.5
CIN = 100μF, Panasonic, EEVFK1E101P
COUT = 47μF, Vishay Sprague, 594D476X_016C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 274kΩ ±1%, 0805
D1 = B220/A, Diodes Inc.
L1 = 150μH, Coilcraft Inc., DO5022P-154
9 to 14
5 0.5
CIN = 100μF, Panasonic, EEVFK1E101P
COUT = 33μF, Vishay Sprague, 594D336X_016C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 274kΩ ±1%, 0805
D1 = B220/A, Diodes Inc.
L1 = 220μH, Coilcraft Inc., DO5022P-224
3.3 0.5
CIN = 100μF, Panasonic, EEVFK1H101P
COUT = 47μF, Vishay Sprague, 594D476X_016C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = B240/A, Diodes Inc.
L1 = 150μH, Coilcraft Inc., DO5022P-154
5 0.5
CIN = 100μF, Panasonic, EEVFK1H101P
COUT = 33μF, Vishay Sprague, 594D336X_016C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = B240/A, Diodes Inc.
L1 = 220μH, Coilcraft Inc., DO5022P-224
18 to 36
12 0.5
CIN = 100μF, Panasonic, EEVFK1H101P
COUT = 15μF, Vishay Sprague, 594D156X_025C2T
CBST = 0.1μF, 0805
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = B240/A, Diodes Inc.
L1 = 330μH, Coilcraft Inc., DO5022P-334
Table 2. Typical External Components Selection (Circuit of Figure 2) (continued)
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
14 ______________________________________________________________________________________
SUPPLIER PHONE FAX WEBSITE
AVX 843-946-0238 843-626-3123 www.avxcorp.com
Coilcraft 847-639-6400 847-639-1469 www.coilcraft.com
Diodes Incorporated 805-446-4800 805-446-4850 www.diodes.com
Nichicon 858-824-1515 858-824-1525 www.nichicon.com
Panasonic 714-373-7366 714-737-7323 www.panasonic.com
SANYO 619-661-6835 619-661-1055 www.sanyo.com
TDK 847-803-6100 847-390-4405 www.component.tdk.com
Vishay 402-563-6866 402-563-6296 www.vishay.com
Table 3. Component Suppliers
MAX5033
CIN
47μF
COUT
33μF
L1
220μH
FB
VOUT
5V AT 0.5A
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)
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
______________________________________________________________________________________ 15
MAX5033B
CIN
47μF
COUT
68μF
L1
220μH
FB
VOUT
5V AT 0.5A
BST
LX
SGND
0.1μF
0.1μF
GND
VIN
7.5V TO 36V VIN
R1
Rt
Ct D1
B240
VD
ON/OFF
MAX5033A
C'IN
68μF
C'OUT
68μF
L1'
150μH
FB
V'OUT
3.3V AT 0.5A
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
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
16 ______________________________________________________________________________________
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 SO/PDIP S8+5 21-0041
Package Information
For the latest package outline information and land patterns, 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.
MAX5033
500mA, 76V, High-Efficiency, MAXPower
Step-Down DC-DC Converter
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________
17
© 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 9/03 Initial release —
1 5/04 New product update 1–7, 10
2 6/04 Removed future product asterisk and made specification changes 1, 2, 3
3 1/07 Modified Absolute Maximum Ratings specifications 2
4 4/10 Corrected inconsistencies in Absolute Maximum Ratings and Electrical
Characteristics table 1, 2, 3, 4, 17