Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - DC/DC voltage regulator Boost SOT 23 6

General Description

The MAX5025–MAX5028 constant-frequency, pulse-

width 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 architec-

ture 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, 6-

pin 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

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

GND

16LX

PGND

MAX5025–

MAX5028

SOT23-6

TOP VIEW

SHDN

Pin Configuration

OUT

30V

C1 C2

= 4.5V TO 11V

(MAX5027)

= 3V TO 11V

(MAX5028)

GND

PGND

MAX5027

MAX5028

SHDN

Typical Operating Circuit

19-2239; Rev 2; 3/09

EVALUATION KIT

AVAILABLE

Ordering Information

PA RT

TEMP RANGE PIN- PACK AGE

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

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.

Summary of content (13 pages)

PAGE 1
9-2239; Rev 2; 3/09 KIT ATION EVALU E L B AVAILA 500kHz, 36V Output, SOT23, PWM Step-Up DC-DC Converters 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.
PAGE 2
MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters ABSOLUTE MAXIMUM RATINGS VCC to GND ............................................................-0.3V to +12V PGND to GND .......................................................-0.1V to +0.1V FB to GND (MAX5025/MAX5026)...............-0.3V to (VCC + 0.3V) FB to GND (MAX5027/MAX5028)...........................-0.3V to +40V SHDN to GND.............................................-0.3V to (VCC + 0.3V) LX to GND ...............................
PAGE 3
500kHz, 36V Output, SOT23, Step-Up DC-DC Converters 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) PARAMETER FB Set Point SYMBOL VFB FB Input Bias Current IFB Output Voltage Adjustment Range CONDITIONS MIN TYP MAX MAX5025, VCC = 4.5V to 11V 1.19 1.25 1.31 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.
PAGE 4
Typical Operating Characteristics (VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.) EFFICIENCY vs. LOAD CURRENT (VOUT = 12V) 40 MAX5026 VCC = 5V, VOUT = 12V CIRCUIT OF FIGURE 2. R1 = 147kΩ, R2 = 16.2kΩ 30 20 10 80 70 40 MAX5026 VCC = 5V, VOUT = 12V CIRCUIT OF FIGURE 2. R1 = 147kΩ, R2 = 13kΩ 30 10 60 2 4 6 8 10 MAX5026 VCC = 5V, VOUT = 24V CIRCUIT OF FIGURE 2. R1 = 147kΩ, R2 = 8.07kΩ 10 0 0 2 4 6 8 0 1 2 3 4 5 LOAD CURRENT (mA) EFFICIENCY vs.
PAGE 5
00kHz, 36V Output, SOT23, Step-Up DC-DC Converters EXITING SHUTDOWN ENTERING SHUTDOWN MAX5025-28 toc10 OUTPUT VOLTAGE 20V/div MAX5025-28 toc11 30V 30V 5V INDUCTOR CURRENT 50mA/div 5V OUTPUT VOLTAGE 20V/div 5V SHUTDOWN VOLTAGE 5V/div 5V 0V SHUTDOWN VOLTAGE 5V/div 2ms/div 100ms/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 1mA. CIRCUIT OF FIGURE 3 MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 1mA.
PAGE 6
Typical Operating Characteristics (continued) (VCC = 5V, VOUT = 30V, TA = +25°C, unless otherwise noted.) HEAVY-LOAD SWITCHING WAVEFORM WITHOUT RC FILTER HEAVY-LOAD SWITCHING WAVEFORM WITH RC FILTER MAX5025-28 toc16 MAX5025-28 toc17 VOUT 5mV/div AC-COUPLED VOUT 1mV/div AC-COUPLED LX PIN 20V/div LX PIN 20V/div 0V IL 200mA/div 0mA 0V IL 200mA/div 0mA 1μs/div 1μs/div MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 4mA. CIRCUIT OF FIGURE 2 MAX5026, VCC = 5V, VOUT = 30V, ILOAD = 4mA.
PAGE 7
500kHz, 36V Output, SOT23, Step-Up DC-DC Converters SWITCH ON-RESISTANCE vs. TEMPERATURE LX LEAKAGE CURRENT vs. TEMPERATURE 2.5 2.0 VCC = 5V 1.5 0.040 0.035 0.030 0.025 0.020 0.015 0.010 1.0 0.005 VCC = 11V 0 0.5 0 20 40 60 0 20 40 60 TEMPERATURE (°C) LOAD REGULATION MAX5026 MAXIMUM LOAD CURRENT vs.
PAGE 8
MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Pin Description PIN MAX5025/ MAX5026 MAX5027/ MAX5028 NAME FUNCTION 1 1 PGND Power Ground. Connect directly to local ground plane. Use a star ground configuration for low noise. 2 2 GND Ground. Connect directly to local ground plane. 3 — FB Feedback Pin. Reference voltage is approximately 1.25V. Connect resistive-divider tap here. Minimize trace area at FB. See Setting the Output Voltage section. — 3 FB Feedback Pin.
PAGE 9
500kHz, 36V Output, SOT23, Step-Up DC-DC Converters ULVO 3 FB -A OSCILLATOR MAIN PWM COMPARATOR SHDN 4 LX 6 PGND 1 CONTROL LOGIC +A REF THERMAL SHUTDOWN +C 2 GND 5 VCC -C CURRENTLIMIT COMPARATOR N L = MAX5025 MAX5026 Figure 1. Functional Diagram Use the following formula to calculate the upper bound of the inductor value at different output voltages and output currents. This is the maximum inductance value for discontinuous mode operation.
PAGE 10
MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Capacitor Selection For a design in which VIN = 5V, VOUT = 30V, IOUT = 4mA, η = 0.5, and TS = 2µs, LUPPER = 87µH Output Filter Capacitor The output filter capacitor should be 1µF or greater. To achieve low output ripple, a capacitor with low ESR, low ESL, and high capacitance value should be selected. For very low output ripple applications, the output of the boost converter can be followed by an RC filter to further reduce the ripple.
PAGE 11
500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Figures 2 and 3 show the MAX5025/MAX5026 operating in a 30V boost application. Figure 3 has an RC filter to reduce noise at the output. These circuits provide output currents greater than 4mA with an input voltage of 5V or greater. They are designed by following the Design Procedure section. Operating characteristics of these circuits are shown in the Typical Operating Characteristics section.
PAGE 12
MAX5025–MAX5028 500kHz, 36V Output, SOT23, Step-Up DC-DC Converters Selector Guide PART OUTPUT FREQUENCY TOLERANCE FB SET POINT TOLERANCE INPUT VOLTAGE MAX5025 Adjustable -31% to +100% ±5% 4.5V to 11V MAX5026 Adjustable -18% to +34% ±3% 3V to 11V MAX5027 Fixed 30V -31% to +100% ±5% 4.
PAGE 13
500kHz, 36V Output, SOT23, Step-Up DC-DC Converters REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 10/01 Initial release — 1 12/01 Released the MAX5027 1 2 3/09 Revised the Absolute Maximum Ratings section. 2 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.