Maxim MAX5025EUT-T, MAX5026EUT-T, MAX5027EUT-T, MAX5028EUT-T Schematic [ru]

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

Pin Configuration

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

PARAMETER

CONDITIONS

UNITS

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.