AVAILABLE
For pricing, delivery, and
ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
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.
Applications
Automotive
Consumer Electronics
Industrial
Distributed Power
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
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
19-2988; Rev 5; 5/11
Pin Configuration
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
EVALUATION KIT AVAILABLE
Ordering Information
PART TEMP RANGE
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
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
PINPACKAGE
OU TPU T
VO LTA GE
( V)
3.3
5.0
V
IN
7.5V TO 76V
V
68µF
R1
ON
OFF
R2
IN
MAX5035
ON/OFF
SGND
GND
BST
0.1µF
0.1µF
100µH
D1
50SQ100
LX
FB
VD
68µF
V
OUT
5V
TOP VIEW
BST
SGND
1
VD
2
MAX5035
3
FB
4
SO/PDIP
8
7
6
5
LX
V
IN
GND
ON/OFF
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.)
V
IN
.........................................................................-0.3V to +80V
SGND ....................................................................-0.3V to +0.3V
LX.................................................................-0.8V to (V
IN
+ 0.3V)
BST ...............................................................-0.3V to (V
IN
+ 10V)
BST (transient < 100ns)................................-0.3V to (V
IN
+ 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
V
OUT
Short-Circuit Duration (VIN≤ 40V)........................Indefinite
VD Short-Circuit Duration ..............................................Indefinite
Continuous Power Dissipation (T
A
= +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, V
ON/OFF
= +12V, I
OUT
= 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical Application Circuit.
)
MAX5035
2
Maxim Integrated
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Voltage Range V
Undervoltage Lockout UVLO 5.2 V
Output Voltage V
Feedback Voltage V
Quiescent Supply Current I
Shutdown Current I
Peak Switch Current Limit I
MAX5035A 7.5 76.0
MAX5035B 7.5 76.0
IN
MAX5035C 15 76
MAX5035D/E 7.5 76.0
MAX5035A
OUT
SHDN
LIM
MAX5035B
MAX5035C
VIN = 7.5V to 76V, MAX5035D/E 1.192 1.221 1.250
FB
VIN = 7.5V to 76V, MAX5035E 1.185 1.221 1.250
VIN = 12V, I
VIN = 12V, I
VIN = 24V, I
= 12V, V
V
IN
MAX5035D/E
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
Q
VFB = 1.3V, MAX5035D 270 440
VFB = 1.3V, MAX5035E 340 460
V
(Note 1) 1.30 1.9 2.50 A
= 0V, VIN = 7.5V to 76V 10 45 µA
ON/OFF
V
= 7.5V to 76V,
IN
I
= 20mA to 1A
OUT
V
= 7.5V to 76V,
IN
I
= 20mA to 1A
OUT
V
= 15V to 76V,
IN
I
= 20mA to 1A
OUT
= 0.5A, MAX5035A 86
LOAD
= 0.5A, MAX5035B 90
LOAD
= 0.5A, MAX5035C 94Efficiency η
LOAD
OUT
= 5V, I
LOAD
= 0.5A,
3.185 3.3 3.415
4.85 5.0 5.15
11.64 12 12.36
90
V
V
V
%
µA
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued) (MAX5035_U_ _)
(VIN= +12V, V
ON/OFF
= +12V, I
OUT
= 0, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C. See the
Typical Application Circuit.
)
)
ELECTRICAL CHARACTERISTICS (MAX5035_A_ _)
(VIN= +12V, V
ON/OFF
= +12V, I
OUT
= 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
3
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Switch Leakage Current I
Switch On-Resistance R
PFM Threshold I
FB Input Bias Current I
ON/OFF CONTROL INPUT
ON/OFF Input-Voltage Threshold V
ON/OFF Input-Voltage Hysteresis V
ON/OFF Input Current I
ON/OFF Operating Voltage
Range
OSCILLATOR
Oscillator Frequency f
Maximum Duty Cycle D
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/∆IVD0 to 5mA 150 Ω
PACKAGE THERMAL CHARACTERISTICS
Thermal Resistance
(Junction to Ambient)
THERMAL SHUTDOWN
Thermal-Shutdown Junction
Temperature
Thermal-Shutdown Hysteresis T
OL
DS(ON
PFM
ON/OFF
HYST
ON/OFFVON/OFF
V
ON/OFF
OSC
MAX
θ
T
HYST
VIN = 76V, V
I
SWITCH
Minimum switch current in any cycle 55 85 130 mA
MAX5035D/E -150 +0.01 +150 nA
B
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
MAX5035D/E 95 %
SO package (JEDEC 51) 170
JA
DIP package (JEDEC 51) 110
SH
= 1A 0.40 0.80 Ω
= 0V to V
= 0V, VLX = 0V 0.01 1 µA
ON/OFF
100 mV
IN
109 125 135 kHz
10 150 nA
+160 °C
20 °C
76 V
V
°C/W
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input Voltage Range V
Undervoltage Lockout UVLO 5.2 V
Output Voltage V
MAX5035A 7.5 76.0
MAX5035B 7.5 76.0
IN
MAX5035C 15 76
MAX5035D/E 7.5 76.0
= 7.5V to 76V,
V
IN
I
= 20mA to 1A
OUT
= 7.5V to 76V,
V
IN
= 20mA to 1A
I
OUT
= 15V to 76V,
V
IN
I
= 20mA to 1A
OUT
3.185 3.3 3.415
4.825 5.0 5.175
11.58 12 12.42
OUT
MAX5035A
MAX5035B
MAX5035C
V
V
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
ELECTRICAL CHARACTERISTICS (MAX5035_A_ _) (continued)
(VIN= +12V, V
ON/OFF
= +12V, I
OUT
= 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
CONDITIONS
UNITS
VIN = 7.5V to 76V, MAX5035D
Feedback Voltage V
FB
VIN = 7.5V to 76V, MAX5035E
V
VIN = 12V, I
LOAD
= 0.5A, MAX5035A 86
VIN = 12V, I
LOAD
= 0.5A, MAX5035B 90
VIN = 24V, I
LOAD
= 0.5A, MAX5035C 94
Efficiency η
V
IN
= 12V, V
OUT
= 5V, I
LOAD
= 0.5A,
MAX5035D/E
90
%
VFB = 3.5V, VIN = 7.5V to 76V, MAX5035A
440
VFB = 5.5V, VIN = 7.5V to 76V, MAX5035B
440
VFB = 13V, VIN = 15V to 76V, MAX5035C
440
VFB = 1.3V, MAX5035D
440
Quiescent Supply Current I
Q
VFB = 1.3V, MAX5035E
460
µA
Shutdown Current I
SHDN
V
ON/OFF
= 0V, VIN = 7.5V to 76V 10 45 µA
Peak Switch Current Limit I
LIM
(Note 1)
1.9
A
VIN = 76V, V
ON/OFF
= 0V, VLX = 0V 1
Switch Leakage Current I
OL
VIN = 76V, V
ON/OFF
= 0V, VLX = 0V,
MAX5035E
5
µA
Switch On-Resistance
)
I
SWITCH
= 1A
Ω
PFM Threshold I
PFM
Minimum switch current in any cycle 55 85 130 mA
FB Input Bias Current I
B
MAX5035D/E
nA
ON/OFF CONTROL INPUT
Rising trip point for MAX5035A/B/C/D
Rising trip point for MAX5035E
V
V
HYST
mV
ON/OFF Input Current
V
ON/OFF
= 0V to V
IN
10 150 nA
ON/OFF Operating Voltage
Range
76 V
OSCILLATOR
Oscillator Frequency f
OSC
137 kHz
Maximum Duty Cycle D
MAX
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
0 to 5mA
Ω
MAX5035
4
Maxim Integrated
ON/OFF Input-Voltage Threshold V
ON/OFF Input-Voltage Hysteresis
SYMBOL
R
DS(ON
ON/OFF
I
ON/OFF
V
ON/OFF
∆VD/∆I
VD
MIN TYP MAX
1.192 1.221 1.250
1.185 1.221 1.250
270
270
270
270
340
1.30
0.40 0.80
-150 +0.01 +150
1.50 1.69 1.85
1.40 1.65 1.90
105 125
100
150
2.50
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Typical Operating Characteristics
(VIN= 12V, V
ON/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
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
PACKAGE THERMAL CHARACTERISTICS
SO package (JEDEC 51)
Thermal Resistance
(Junction to Ambient)
θ
JA
DIP package (JEDEC 51)
°C/W
THERMAL SHUTDOWN
Thermal-Shutdown Junction
Temperature
T
SH
°C
Thermal-Shutdown Hysteresis T
HYST
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.
V
OUT
vs. TEMPERATURE
(MAX5035AASA, V
OUT
= 3.3V)
MAX5035 toc01
TEMPERATURE (°C)
V
OUT
(V)
3.24
3.28
3.32
3.36
3.40
3.20
I
OUT
= 0.1A
I
OUT
= 1A
100
50
0-50
150-25
25
75
125
V
OUT
vs. TEMPERATURE
(MAX5035DASA, V
OUT
= 5V)
MAX5035 toc02
TEMPERATURE (°C)
V
OUT
(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
I
OUT
= 0.1A
I
OUT
= 1A
LINE REGULATION
(MAX5035AASA, V
OUT
= 3.3V)
MAX5035 toc03
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
65503520
3.24
3.28
3.32
3.36
3.40
3.20
580
I
OUT
= 1A
I
OUT
= 0.1A
LINE REGULATION
(MAX5035DASA, V
OUT
= 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
I
OUT
= 1A
I
OUT
= 0.1A
LOAD REGULATION
(MAX5035AASA, V
OUT
= 3.3V)
MAX5035 toc05
I
LOAD
(mA)
V
OUT
(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, V
OUT
= 5V)
MAX5035 toc06
I
LOAD
(mA)
V
OUT
(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, V
ON/OFF
= +12V, I
OUT
= 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
170
110
+160
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN= 12V, V
ON/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
V
OUT
= 5V
5% DROP IN V
OUT
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
V
OUT
= 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, V
OUT
= 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, V
OUT
= 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, V
OUT
= 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, V
ON/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)
V
OUT
(V)
12963
3
6
9
12
15
0
015
I
OUT
= 0
I
OUT
= 0.3A
I
OUT
= 1A
MAX5035DASA
V
OUT
= 12V
V
ON/OFF
= V
IN
MAX5035DASA
LOAD-TRANSIENT RESPONSE
MAX5035 toc17
400µs/div
B
A
A: V
OUT
, 200mV/div, AC-COUPLED
B: I
OUT
, 500mA/div, 0.1A TO 1A
V
OUT
= 5V
MAX5035DASA
LOAD-TRANSIENT RESPONSE
MAX5035 toc18
400µs/div
B
A
A: V
OUT
, 200mV/div, AC-COUPLED
B: I
OUT
, 500mA/div, 0.5A TO 1A
V
OUT
= 5V
MAX5035DASA
LOAD-TRANSIENT RESPONSE
MAX5035 toc19
400µs/div
B
A
A: V
OUT
, 200mV/div, AC-COUPLED
B: I
OUT
, 500mA/div, 0.1A TO 0.5A
V
OUT
= 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 (I
OUT
= 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 (I
OUT
= 100mA)
MAX5035
Maxim Integrated
7
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Typical Operating Characteristics (continued)
(VIN= 12V, V
ON/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 (I
OUT
= 0)
0
0
MAX5035DASA STARTUP WAVEFORM
(I
O
= 0)
MAX5035 toc23
1ms/div
B
A
A: V
ON/OFF
, 2V/div
B: V
OUT
, 2V/div
0
0
MAX5035DASA STARTUP WAVEFORM
(I
O
= 1A)
MAX5035 toc24
1ms/div
B
A
A: V
ON/OFF
, 2V/div
B: V
OUT
, 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
V
OUT
= 5V
5% DROP IN V
OUT
MAX5035
8
Maxim Integrated
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Pin Description
Block Diagram
MAX5035
Maxim Integrated
9
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.
Output Sense Feedback Connection. For fixed output voltage (MAX5035A, MAX5035B, MAX5035C),
4FB
connect FB to V
voltage-divider to set V
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
7VINInput 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
. For adjustable output voltage (MAX5035D, MAX5035E), use an external resistive
OUT
. VFB regulating set point is 1.22V.
OUT
VD
GND
ON/OFF
1.69V
ENABLE
REGULATOR
(FOR DRIVER)
REGULATOR
(FOR ANALOG)
V
REF
OSC
RAMP
CPFM
CILIM
I
REF-PFM
I
REF-LIM
HIGH-SIDE
CURRENT
SENSE
V
IN
BST
MAX5035
CLK
FB
R
h
x1
R
l
TYPE 3
COMPENSATION
V
REF
EAMP
RAMP
CPWM
CONTROL
LOGIC
THERMAL
SHUTDOWN
LX
SGND
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 VINsupply 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 VINto 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 V
UVLO(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 VINand allows operation to start
when VINrises above 5.2V (typ). This feature can be
used only when VINrise time is faster than 2ms. For
slower VINrise 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 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:
Figure 1. Adjustable Output Voltage
MAX5035
10
Maxim Integrated
R
V
UVLO TH()
⎛
⎜
⎝
1
⎞
⎟
⎠
R
2
×1
185
V
.=+
−
(.)
V
R
3
OUT
.
122
122
4=
×
R
V
IN
7.5V TO 76V
68µF
V
R1
R2
IN
ON/OFF
MAX5035D
SGND
GND
LX
BST
FB
VD
0.1µF
0.1µF
100µH
D1
50SQ100
41.2kΩ
13.3kΩ
V
OUT
5V
C
OUT
68µF
R3
R4
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 VINand V
OUT
, the required output
current, and the operating frequency of the circuit. Use
an inductor with a minimum value given by:
where:
I
OUTMAX
is the maximum output current required, and
fSWis the operating frequency of 125kHz. Use an inductor with a maximum saturation current rating equal to at
least the peak switch current limit (I
LIM
). 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 efficiency. Avoid higher than necessary reverse-voltage
Schottky rectifiers that have higher forward-voltage
drops. Use a Schottky rectifier with forward-voltage
drop (V
FB
) 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 ∆V
Q
(caused by the
capacitor discharge) and ∆V
ESR
(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:
I
OUT
is the maximum output current of the converter
and fSWis the oscillator switching frequency (125kHz).
For example, at VIN= 48V, V
OUT
= 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.
ESR
V
I
I
IN
ESR
OUT
=
+
∆
∆
LL
IN
OUT
C
I
2
⎛
⎝
⎜
⎞
⎠
⎟
=
×
DDD
Vf
where
QSW
()
:
1−
×∆
()
,∆I
VV V
Vf L
L
IN OUT OUT
IN SW
=
−×
××
D
V
V
OUT
IN
=
Table 1. Diode Selection
MAX5035
Maxim Integrated
11
VV D
−×
()
=
IN OUT
If
××
.03
OUTMAX SW
L
V
OUT
D
=
V
IN
V
(V) DIODE PART NUMBER MANUFACTURER
IN
7.5 to 36
7.5 to 56
7.5 to 76
15MQ040N IR
B240A Diodes, Inc.
B240 Central Semiconductor
MBRS240, MBRS1540 ON Semiconductor
MBRD360, MBR3060 ON Semiconductor
30BQ060 IR
50SQ100, 50SQ80 IR
B360A Diodes, Inc.
CMSH3-60 Central Semiconductor
MBRM5100 Diodes, Inc.
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:
I
PRMS
is the input switch RMS current, I
AVGIN
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.
The output ripple is comprised of ∆VOQ(caused by the
capacitor discharge) and ∆V
OESR
(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 ripple using the following equations:
The MAX5035 has an internal soft-start time (t
SS
) of
400µs. It is important to keep the output rise time at
startup below tSSto 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 (t
RESPONSE
) 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:
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”
MAX5035
12
Maxim Integrated
III
=−
CRMS PRMS AVGIN
where :
IIIII
=++×
PRMS PK DC PK DC
I
AVGIN
II
PK OUT
andD
()
V
OOUT OUT
=
V
IN
=+ =−
∆∆
V
OUT
=
V
IN
2 22
I
L
D
×
3
22
×
×
I
L
,
22
()
I
η
II
DC OUT
f
=
Z
×× ×
2 π
1
C ESR
OUT OUT
V
∆
ESR
OUT
C
≈
OUT
ESR
OUT
It
C
OUT
STEP R ESPONSE
=
OESR
=
I
∆
L
I
∆
L
Vf
××
∆22.
OQ SW
V
∆
OESR
=
I
STEP
×
V
∆
OQ
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 V
IN
and LX for heatsinking.
Figure 2. Fixed Output Voltages
Table 2. Typical External Components Selection (Circuit of Figure 2)
Application Circuits
MAX5035
Maxim Integrated
13
V
IN
R1
R2
C
IN
V
IN
MAX5035
ON/OFF
SGND
GND
BST
0.1µF
LX
FB
VD
0.1µF
L1
D1
C
OUT
V
OUT
VIN (V) V
OUT
(V) I
OUT
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 12 1
(A) EXTERNAL COMPONENTS
= 68µF, Panasonic, EEVFK2A680Q
C
IN
C
= 68µF, Vishay Sprague, 594D686X_010C2T
OUT
= 0.1µF, 0805
C
BST
R1 = 1MΩ ±1%, 0805
R2 = 384kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 100µH, Coilcraft Inc., DO5022P-104
C
= 68µF, Panasonic, EEVFK2A680Q
IN
= 68µF, Vishay Sprague, 594D68X_010C2T
C
OUT
C
= 0.1µF, 0805
BST
R1 = 1MΩ ±1%, 0805
R2 = 384kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 100µH, Coilcraft Inc., DO5022P-104
C
= 68µF, Panasonic, EEVFK2A680Q
IN
= 15µF, Vishay Sprague, 594D156X0025C2T
C
OUT
C
= 0.1µF, 0805
BST
R1 = 1MΩ ±1%, 0805
R2 = 139kΩ ±1%, 0805
D1 = 50SQ100, IR
L1 = 220µH, Coilcraft Inc., DO5022P-224
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Table 2. Typical External Components Selection (Circuit of Figure 2) (continued)
MAX5035
14
Maxim Integrated
VIN (V) V
9 to 14
18 to 36
(V) I
OUT
3.3 1
51
3.3 1
51
(A) EXTERNAL COMPONENTS
OUT
C
= 220µF, Panasonic, EEVFK1E221P
IN
C
= 68µF, Vishay Sprague, 594D686X_010C2T
OUT
= 0.1µF, 0805
C
BST
R1 = 1MΩ ±1%, 0805
R2 = 274kΩ ±1%, 0805
D1 = B220, Diodes Inc.
L1 = 100µH, Coilcraft Inc., DO5022P-104
C
= 220µF, Panasonic, EEVFK1E221P
IN
C
= 68µF, Vishay Sprague, 594D686X_010C2T
OUT
= 0.1µF, 0805
C
BST
R1 = 1MΩ ±1%, 0805
R2 = 274kΩ ±1%, 0805
D1 = B220, Diodes Inc.
L1 = 100µH, Coilcraft Inc., DO5022P-104
C
= 220µF, Panasonic, EEVFK1H221P
IN
= 68µF, Vishay Sprague, 594D686X_010C2T
C
OUT
C
= 0.1µF, 0805
BST
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = MBRS2040, ON Semiconductor
L1 = 100µH, Coilcraft Inc., DO5022P-104
C
= 220µF, Panasonic, EEVFK1H221P
IN
= 68µF, Vishay Sprague, 594D686X_010C2T
C
OUT
C
= 0.1µF, 0805
BST
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = MBRS2040, ON Semiconductor
L1 = 100µH, Coilcraft Inc., DO5022P-104
12 1
C
= 220µF, Panasonic, EEVFK1H221P
IN
C
= 15µF, Vishay Sprague, 594D156X_0025C2T
OUT
= 0.1µF, 0805
C
BST
R1 = 1MΩ ±1%, 0805
R2 = 130kΩ ±1%, 0805
D1 = MBRS2040, ON Semiconductor
L1 = 220µH, Coilcraft Inc., DO5022P-224
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
Table 3. Component Suppliers
Figure 3. Load Temperature Monitoring with ON/OFF (Requires Accurate VIN)
MAX5035
Maxim Integrated
15
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
MAX5035
PTC*
V
IN
12V
C
IN
68µF
*LOCATE PTC AS CLOSE TO HEAT-DISSIPATING COMPONENTS AS POSSIBLE.
Ct
ON/OFF
V
IN
Rt
SGND
GND
FB
BST
LX
VD
0.1µF
0.1µF
D1
B240
L1
100µH
V
OUT
5V AT 1A
C
OUT
68µF
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
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)
/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
GND
GND
FB
BST
LX
VD
0.1µF
FB
BST
LX
VD
0.1µF
0.1µF
0.1µF
D1
B240
D1'
B240
L1
220µH
L1'
100µH
V
V'
3.3V
OUT
5V
V
7.5V TO 36V
MAX5035B
R1
IN
C
68µF
IN
Ct
ON/OFF
V
IN
Rt
SGND
MAX5035A
C'
68µF
R1'
IN
Ct'
ON/OFF
V
IN
Rt'
SGND
OUT
C
OUT
68µF
C'
OUT
68µF
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
M AX 5035C AS A/V + -40°C to +125°C 8 SO
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
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
OU TPU T
VO LTA GE
( V)
12
ADJ
ADJ
1A, 76V, High-Efficiency MAXPower
Step-Down DC-DC Converter
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.
REVISION
NUMBER
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
DATE
DESCRIPTION
CHANGED
PAGES
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