General Description
The MAX5025–MAX5028 constant-frequency, pulsewidth modulating (PWM), low-noise boost converters
are intended for low-voltage systems that often need a
locally generated high voltage. These devices are
capable of generating low-noise, high output voltages
required for varactor diode biasing in TV tuners, set-top
boxes, and PCI cable modems. The MAX5025–
MAX5028 operate from as low as 3V and switch at
500kHz.
The constant-frequency, current-mode PWM architecture provides for low output noise that is easy to filter. A
40V lateral DMOS device is used as the internal power
switch, making the devices ideal for boost converters
up to 36V. The MAX5025/MAX5026 adjustable versions
require the use of external feedback resistors to set the
output voltage. The MAX5027/MAX5028 offer a fixed
30V output. These devices are available in a small, 6pin SOT23 package.
Applications
TV Tuner Power Supply
Low-Noise Varactor Diode Biasing
Set-Top Box Tuner Power Supply
PCI Cable Modem
Voice-Over-Cable
LCD Power Supply
Avalanche Photodiode Biasing
Features
♦ Input Voltage Range:
3V to 11V (MAX5026/MAX5028)
4.5V to 11V (MAX5025/MAX5027)
♦ Wide Output Voltage Range: V
CC
to 36V
♦ Output Power: 120mW (max)
♦ User-Adjustable Output Voltage with
MAX5025/MAX5026 Using External Feedback
Resistors
♦ Fixed 30V Output Voltage: MAX5027/MAX5028
♦ Internal 1.3Ω (typ), 40V Switch
♦ Constant PWM Frequency Provides Easy Filtering
in Low-Noise Applications
♦ 500kHz (typ) Switching Frequency
♦ 1μA (max) Shutdown Current
♦ Small, 6-Pin SOT23 Package
MAX5025–MAX5028
500kHz, 36V Output, SOT23,
PWM Step-Up DC-DC Converters
________________________________________________________________
Maxim Integrated Products
1
V
OUT
30V
C1 C2
L1
VCC = 4.5V TO 11V
(MAX5027)
V
CC
= 3V TO 11V
(MAX5028)
D1
V
CC
GND
FB
PGND
LX
MAX5027
MAX5028
SHDN
Typical Operating Circuit
19-2239; Rev 2; 3/09
EVALUATION KIT
AVAILABLE
Ordering Information
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Selector Guide appears at end of data sheet.
PA RT
MAX5025EUT-T -40°C to +85°C 6 SOT23-6
MAX5026EUT-T -40°C to +85°C 6 SOT23-6
MAX5027EUT-T -40°C to +85°C 6 SOT23-6
MAX5028EUT-T -40°C to +85°C 6 SOT23-6
TEMP RANGE PIN- PACK AGE
TOP VIEW
16LX
PGND
GND
MAX5025–
2
MAX5028
FB
34
SOT23-6
5V
CC
SHDN
MAX5025–MAX5028
500kHz, 36V Output, SOT23,
Step-Up DC-DC Converters
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= 5V, SHDN = VCC, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
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.
VCCto GND............................................................-0.3V to +12V
PGND to GND .......................................................-0.1V to +0.1V
FB to GND (MAX5025/MAX5026)...............-0.3V to (V
CC
+ 0.3V)
FB to GND (MAX5027/MAX5028)...........................-0.3V to +40V
SHDN to GND.............................................-0.3V to (V
CC
+ 0.3V)
LX to GND ..............................................................-0.3V to +45V
Peak LX Current ................................................................600mA
Operating Temperature Range ...........................-40°C to +85°C
Continuous Power Dissipation (T
A
= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C)..........695.7mW
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering 10s) ..................................+300°C
SUPPLY VOLTAGE
MAX5026/MAX5028 3.0 11
Input Voltage Range V
CC
MAX5025/MAX5027 4.5 11
V
Undervoltage Lockout
Rise/fall, hysteresis = 3mV
V
Supply Current I
CC
MAX5025/MAX5026, FB = 1.4V
MAX5027/MAX5028, FB = 35V
µA
Shutdown Current I
SHDN
SHDN = GND
1µA
BOOST CONVERTER
MAX5025/MAX5027
Switching Frequency f
SW
MAX5026/MAX5028, VCC = 3.3V
670
kHz
MAX5025/MAX5027,
I
LOAD
= 2mA, VCC = 4.5V to 11V,
V
OUT
= 30V
Line Regulation
MAX5026/MAX5028,
I
LOAD
= 0.5mA, VCC = 3V to 11V,
V
OUT
= 30V
%/V
MAX5025/MAX5027,
V
CC
= 5V, I
LOAD
= 0 to 4mA,
V
OUT
= 30V
2.0
Load Regulation
MAX5026/MAX5028,
V
CC
= 3.3V, I
LOAD
= 0 to 1mA,
V
OUT
= 30V
1.0
%
Thermal Shutdown
°C
Thermal Shutdown Hysteresis 2°C
SYMBOL
MIN TYP MAX
V
UVLO
2.25 2.65 2.95
345 500 1000
410 500
350 1000
0.01
0.25
0.25
140
MAX5025–MAX5028
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 5V, SHDN = VCC, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Note 1: All devices are 100% production tested at TA= +25°C. All temperature limits are guaranteed by design.
Note 2: Switch current-limit accuracy is typically ±20% and is a function of the input voltage. I
LIM
= (VIN/5) (260mA).
500kHz, 36V Output, SOT23,
Step-Up DC-DC Converters
_______________________________________________________________________________________ 3
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX5025, VCC = 4.5V to 11V 1.19 1.25 1.31
FB Set Point V
FB Input Bias Current I
Output Voltage
Adjustment Range
LX OUTPUT
LX On-Resistance R
Switch Current Limit I
LX Leakage Current VLX = 40V
LOGIC INPUT: SHDN
Input Low Level V
Input High Level V
Input Bias Current -1 1 µA
FB
FB
ON
LIM
MAX5027, VCC = 4.5V to 11V 28.5 30.0 31.5
MAX5026, VCC = 3.3V to 11V 1.212 1.25 1.288
MAX5028, VCC = 3.3V to 11V 29.0 30 31
MAX5025/MAX5026, FB = 1V 110 310 nA
MAX5027/MAX5028, FB = 30V 100 170 µA
MAX5025/MAX5026 V
MAX5026/MAX5028,
V
= 3V
ILX = 40mA
Note 2 260 mA
IL
IH
CC
VCC = 5V 1.3 3.0
V
= 11V 1.0 2.5
CC
MAX5025/MAX5026,
V
= 1.4V
FB
MAX5027/MAX5028,
V
= 35V
FB
+ 1 36 V
CC
2.0 4.0
0.01 10 µA
2.4 V
0.8 V
V
Ω
MAX5025–MAX5028
500kHz, 36V Output, SOT23,
Step-Up DC-DC Converters
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= 5V, V
OUT
= 30V, TA= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
= 12V)
(V
90
80
70
60
50
40
EFFICIENCY (%)
30
20
10
0
0246810
OUT
CIRCUIT OF FIGURE 2.
R1 = 147kΩ, R2 = 16.2kΩ
LOAD CURRENT (mA)
MAX5026
V
CC
V
OUT
= 5V,
= 12V
MAX5025-28 toc01
EFFICIENCY (%)
EFFICIENCY vs. LOAD CURRENT
= 30V)
(V
70
60
50
40
30
EFFICIENCY (%)
20
10
0
01234
OUT
CIRCUIT OF FIGURE 2.
R1 = 147kΩ, R2 = 6.34kΩ
LOAD CURRENT (mA)
MAX5026
V
CC
V
OUT
= 5V,
= 30V
MAX5025-28 toc04
STARTUP VOLTAGE (V)
MAX5026
NO LOAD SUPPLY CURRENT
vs. SUPPLY VOLTAGE
16
CIRCUIT OF FIGURE 2
14
12
10
NO LOAD SUPPLY CURRENT (mA)
= 30V
V
OUT
8
6
4
2
0
357911
SUPPLY VOLTAGE (V)
MAX5025-28 toc07
SUPPLY CURRENT (μA)
EFFICIENCY vs. LOAD CURRENT
= 15V)
(V
90
80
70
60
50
40
30
20
10
0
04268
OUT
CIRCUIT OF FIGURE 2.
R1 = 147kΩ, R2 = 13kΩ
LOAD CURRENT (mA)
MAX5026
V
CC
V
OUT
= 5V,
= 12V
MAX5025-28 toc02
EFFICIENCY (%)
MAX5026 MINIMUM STARTUP VOLTAGE
vs. LOAD CURRENT
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
01234
LOAD CURRENT (mA)
MAX5025-28 toc05
SUPPLY CURRENT (μA)
SUPPLY CURRENT vs. TEMPERATURE
850
750
650
550
450
350
250
150
-40 0 20-20 40 60 80
VCC = 11V
VCC = 9V
VCC = 7V
VCC = 5V
VCC = 3V
CURRENT INTO VCC PIN
TEMPERATURE (°C)
MAX5025-28 toc08
SWITCHING FREQUENCY (kHz)
EFFICIENCY vs. LOAD CURRENT
= 24V)
(V
80
70
60
50
40
30
20
10
0
012345
OUT
CIRCUIT OF FIGURE 2.
R1 = 147kΩ, R2 = 8.07kΩ
LOAD CURRENT (mA)
MAX5026
V
CC
V
OUT
= 5V,
= 24V
MAX5026/MAX5028
SUPPLY CURRENT vs. SUPPLY VOLTAGE
500
450
400
350
300
250
200
150
100
50
0
036912
CURRENT INTO VCC PIN
DEVICE NOT SWITCHING
SUPPLY VOLTAGE (V)
MAX5026
SWITCHING FREQUENCY vs. TEMPERATURE
650
600
550
500
450
400
350
300
250
200
-40 0 20-20 40 60 80
CIRCUIT OF FIGURE 2.
TEMPERATURE (°C)
VCC = 5V
V
OUT
= 30V
MAX5025-28 toc03
MAX5025-28 toc06
MAX5025-28 toc09
MAX5025–MAX5028
Typical Operating Characteristics (continued)
(VCC= 5V, V
OUT
= 30V, TA= +25°C, unless otherwise noted.)
500kHz, 36V Output, SOT23,
Step-Up DC-DC Converters
_______________________________________________________________________________________
5
OUTPUT
VOLTAGE
20V/div
INDUCTOR
CURRENT
50mA/div
SHUTDOWN
VOLTAGE
5V/div
5V
MAX5026, V
CIRCUIT OF FIGURE 3
EXITING SHUTDOWN
2ms/div
= 5V, V
CC
OUT
= 30V, I
MAX5025-28 toc10
LOAD
= 1mA.
LIGHT-LOAD SWITCHING WAVEFORM
WITHOUT RC FILTER
MAX5025-28 toc12
30V
5V
30V
OUTPUT
VOLTAGE
20V/div
SHUTDOWN
VOLTAGE
5V/div
ENTERING SHUTDOWN
100ms/div
MAX5026, V
CIRCUIT OF FIGURE 3
CC
= 5V, V
OUT
LIGHT-LOAD SWITCHING WAVEFORM
WITH RC FILTER
= 30V, I
MAX5025-28 toc11
LOAD
5V
5V
0V
= 1mA.
MAX5025-28 toc13
V
OUT
2mV/div
AC-COUPLED
LX PIN
20V/div
100mA/div
V
OUT
5mV/div
AC-COUPLED
LX PIN
20V/div
200mA/div
I
L
1μs/div
MAX5026, V
CIRCUIT OF FIGURE 2
CC
= 5V, V
OUT
= 30V, I
LOAD
= 0.1mA.
MEDIUM-LOAD SWITCHING WAVEFORM
WITHOUT RC FILTER
I
L
MAX5025-28 toc14
0V
0mA
0V
0mA
V
1mV/div
AC-COUPLED
LX PIN
20V/div
100mA/div
V
OUT
1mV/div
AC-COUPLED
LX PIN
20V/div
200mA/div
OUT
I
L
1μs/div
= 5V, V
MAX5026, V
CIRCUIT OF FIGURE 3
CC
OUT
= 30V, I
LOAD
MEDIUM-LOAD SWITCHING WAVEFORM
WITH RC FILTER
I
L
MAX5025-28 toc15
0V
0mA
= 0.1mA.
0V
0mA
MAX5026, V
CIRCUIT OF FIGURE 2
CC
= 5V, V
1μs/div
OUT
= 30V, I
LOAD
= 2mA.
MAX5026, V
CIRCUIT OF FIGURE 3
CC
= 5V, V
1μs/div
OUT
= 30V, I
LOAD
= 2mA.