MP1522EQ - Monolithic Power Systems, Inc.

MP1522

25V Step-Up Converter

in a SOT23-5 Package

MP1522 Rev. 1.9 www.MonolithicPower.com 1

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The Future of Analog IC Technology

DESCRIPTION

The MP1522 is a step up converter that

generates up to a 25V output voltage from a

2.7V to 25V input. It uses a current limited

Variable Frequency control algorithm to

optimize efficiency and minimize external

component size and cost. The internal 0.5

N-Channel MOSFET switch can withstand up to

28V allowing the MP1522 to produce high

output voltage with high efficiency.

The MP1522 includes input under voltage and

over temperature protection. The MP1522 is

available in tiny 5-pin SOT23 and 3x3 QFN6

packages.

EVALUATION BOARD REFERENCE

Board Number Dimensions

EV0022 2.2”X x 1.5”Y x 0.5”Z

FEATURES

• Internal 0.5 Power Switch

• Output Voltage up to 25V

• Up to 90% Efficiency

• Low 1µA Shutdown Current

• Input Under Voltage Protection

• Thermal Shutdown

• Internal Current Limit

• Available in Tiny 5-Pin SOT23 and 6-Pin

3x3 QFN Packages

APPLICATIONS

• Handheld Computers, PDAs

• Cell Phones

• Digital Still and Video Cameras

• Small LCD Displays

“MPS” and “The Future of Analog IC Technology” are Registered

Trademarks of Monolithic Power Systems, Inc.

TYPICAL APPLICATION

MP1522_TAC_S01

MP1522

BIAS

GND

OFF ON V

OUT

20V

3.3V

1nF

RB751

EFFICIENCY (%)

100

LOAD CURRENT (mA)

MP1522_TAC_EC01

Efficiency vs Load Current

with BIAS Tied to VOUT

1 10010 1000

3.3V

5.0V

10V

VOUT = 12V

MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE

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PACKAGE REFERENCE

MARKING

TOP VIEW

GND

BIAS

MP1522_PD01-TSOT23-5

Part Number* Package Temperature

MP1522ET SOT23-5

–20°C to +85°C

MP1522EQ 3x3 QFN6

–20°C to +85°C

* For Tape & Reel, add suffix –Z (eg. MP1522ET–Z)

For Lead Free, add suffix –LF (eg. MP1522ET–LF–Z)

ABSOLUTE MAXIMUM RATINGS (1)

BIAS .............................................. –0.3V to 28V

SW ................................................. –0.5V to 28V

All Other Pins................................... –0.3V to 6V

Junction Temperature...............................150°C

Solder Temperature..................................260°C

Storage Temperature ................–65°C to 150°C

Recommended Operating Conditions (2)

BIAS Supply Voltage ....................... 2.7V to 25V

Output Voltage....................................VIN to 25V

Operating Temperature .............–20°C to +85°C

Thermal Resistance (3) θJA θJC

SOT23-5 ................................ 220 .... 110.. °C/W

3x3 QFN6 ............................... 50 ...... 14... °C/W

Notes:

1) Exceeding these ratings may damage the device.

2) The device is not guaranteed to function outside of its

operating conditions.

3) Measured on approximately 1” square of 1 oz copper.

ELECTRICAL CHARACTERISTICS

VBIAS = VEN = 5.0V, TA = +25°C, unless otherwise noted.

Parameter Symbol Condition Min Typ Max Units

Supply Current (Shutdown) IBIAS (OFF) V

EN = 0V 1 3 µA

Supply Current (Quiescent) IBIAS(ON) V

FB = 1.3V 650 750 µA

Min Off Time, Normal

Operation

TOFF V

FB = 1.23V 300 550 700 ns

Min Off Time, Start-Up (4) T

OFF V

FB = 0V 1.6 µs

Undervoltage Lockout

BIAS Under Voltage Lockout UVLO VBIAS Rising,

100mV Hysteresis (Typical)

2.1 2.3 2.65 V

Enable

EN Threshold VEN Rising 0.8 1.1 2.0 V

EN Hysteresis 60 mV

EN Input Bias Current VEN = 0V, 5V 1 µA

Feedback Comparator

FB Regulation Threshold VFB Falling 1.19 1.23 1.27 V

FB Hysteresis (5) 10 mV

FB Input Bias Current VFB = 1.23V –150 –80 nA

Output Switch

SW On-Resistance (5) R

ON V

BIAS = 5.0V 0.5 0.6 

SW Current Limit 300 450 mA

SW Leakage Current VSW=25V 10 µA

Thermal Shutdown (5) 160 °C

Notes:

4) First 64 pulses after EN switches High

5) Guaranteed by design.

MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE

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PIN FUNCTIONS

Pin # Name Description

1 SW Power Switch Output. SW is the drain of the internal MOSFET switch. Connect the power

inductor and output rectifier to SW. SW can swing between GND and 25V.

2 GND Ground.

3 FB Feedback Input. Connect a resistive voltage divider from the output voltage to FB to set

the output voltage. The feedback regulation threshold is 1.23V.

4 EN Regulator On/Off Control Input. A high voltage at EN turns on the converter, and a low

voltage turns it off. When not used, connect EN to the input source for automatic startup. If

EN is driven over 6V, place a 100k resistor in series with EN.

5 BIAS Internal Power Input. BIAS powers the internal circuitry. Connect BIAS to the output for

more enhancement on the internal MOSFET gate at low VIN. If the input source remains

above 3.0V, BIAS can be connected to the input source to reduce power consumption.

OPERATION

The MP1522 is a step-up converter that

operates from an input voltage as low as 2.7V

and generates an output voltage up to 25V. The

0.5 internal N-Channel MOSFET power switch

is driven with a variable frequency, constant-

peak-current architecture for improved

regulation and low operating current. The 550ns

minimum off-time is extended to 1.6µs during

start-up to yield a smooth glitch free turn-on.

Start-up mode is activated at initial power-up or

when exiting the 1µA shutdown state. The

MP1522 features an internal regulator allowing

it to be powered from the output for improved

low-input voltage operation, or powered from

the input source for reduced power

consumption due to quiescent current.

MP1522_BD01

CONTROL

LOGIC

OFF ON

REGULATOR

L1 D1

INTERNAL

POWER

ERROR

AMP

1.23V

450mA

GND

(2)

(4)

BIAS

(5)

(3)

(1)

C2 C3

CURRENT --

OUT

GND

Figure 1—Functional Block Diagram

MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE

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Variable Frequency

Constant-Peak-Current Operation

When the power MOSFET is turned on the

inductor current increases until the 0.45A

current limit is reached. The Power MOSFET is

then turned off for a minimum of 550ns. At the

end of this 550ns transition if the feedback pin

is still lower than the 1.23V internal reference

the power MOSFET will again be turned on,

otherwise the MP1522 waits until the voltage

drops below the threshold before turning on the

MOSFET again. This process allows for optimal

use of the inductor, while minimizing the output

ripple and size of the output capacitor and

maintaining low operating current.

Setting the Output Voltage

The output voltage is set by a resistive voltage

divider connecting the output voltage to FB. The

voltage divider reduces the output voltage down

by the ratio:

2R1R

OUT +

Solving for VOUT

⎟

⎠

⎞

⎜

⎝

⎛+

=1R

2R1R

VV FBOUT

Where VOUT is the output voltage, and VFB is the

1.23V feedback threshold. Substituting the

feedback threshold voltage:

⎟

⎠

⎞

⎜

⎝

⎛+

=1R

2R1R

V23.1VOUT

R1 can range from 10k to 200k. R2 is

determined the equation:

⎥

⎦

⎤

⎢

⎣

⎡−

⎟

⎠

⎞

⎜

⎝

⎛

1R2R

OUT

For example for an output voltage of 20V and

R1 = 130k the formula yields:

⎥

⎦

⎤

⎢

⎣

⎡−

⎟

⎠

⎞

⎜

⎝

⎛

Ω= 1

V23.1

k1302R

R2 = 2M the closest standard 1% resistor

value.

The feedback divider requires a feed-forward

capacitor connected in parallel with R2. This

capacitor is typically in the range of 1nF-10nF.

On/Off Control

The EN input is used to turn the converter on

and off. A high input at EN turns the converter

on and a low level turns the converter off. When

EN is not being used, connect to the input

source for automatic startup. For inputs greater

than 6V, pull EN to VIN through a 100k

resistor.

Input Capacitor

To reduce noise, use a low ESR/ESL type input

capacitor. A 1µF surface mount ceramic

capacitor close to the input supply side of the

inductor minimizes EMI and ripple current at the

input source. See the section on printed circuit

board layout for reducing noise and emissions.

A bypass capacitor is typically required to

prevent noise at the MP1522. This capacitor

should also be a low ESR/ESL type capacitor.

Place a 0.1µF surface mount ceramic capacitor

between BIAS and GND as close to the

MP1522 as possible.

Output Capacitor

To minimize output voltage ripple and noise use

a low ESR/ESL type output capacitor. Typically

a 1µF surface mount ceramic capacitor is

sufficient. When using aluminum electrolytics,

tantalum or aluminum polymer capacitors the

ESR/ESL dominate the output ripple. See the

section on printed circuit board layout.

Inductor

The inductor stores energy during the power

MOSFET switch on-time. This energy is

transferred to the output during the switch off-

time. Select an inductor whose peak-current

rating is greater than the 450mA peak current

limit of the MP1522. Lower value inductors yield

higher switching frequencies and thus lower

output ripple voltage. However, using too low a

value inductor will cause an increase in peak

current limit due to the delay of the current-limit

comparator. Choose an inductor such that the

peak current limit is reached in 550ns or longer.

The minimum value inductor for this criterion is:

()

HV1031.1L IN

6µ××≥ −

For maximum VIN = 3.3V, use an inductor value

greater than 4.7µH, and for maximum VIN = 5V

use an inductor value greater than 6.8µH.

MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE

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Diode

The high switching frequencies of the MP1522

require the use of fast recovery or Schottky

barrier diodes. In low voltage applications

Schottky barrier diodes are recommended for

maximum efficiency. The reverse breakdown

voltage should be approximately 1.5X the

output voltage.

Printed Circuit Board Layout

The printed circuit board layout is important in

order to minimize noise and prevent erratic

operation. Keep the ground leads short and

robust with minimum lead lengths between the

input and output capacitors and ground. Place

the feedback resistive voltage divider as close

to FB as possible to prevent switching noise

injection into FB. The use of surface mount

capacitors with their low ESL is required to

minimize noise at the MP1522. Use separate

power and quiet ground planes connected

together at a single point whenever possible to

minimize.ground.bounce.

Table 1—Output Current vs. Input Voltage

VIN (V) VOUT (V) IOUT (mA)

3.3 5 67

3.3 12 28

3.3 18 15

3.3 25 10

5 12 44

5 18 32

5 25 19

10 12 122

10 18 75

10 25 51

MP1522_TAC_F02

MP1522 BIAS

GND

OFF ON VOUT

20V

VIN

3.3V

1nF

RB751

Figure 2—Typical Boost Application

MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE

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PACKAGE INFORMATION

SOT23-5

1. Dimensions and tolerances are as per ANSI

2. Package surface to be matte finish VDI 11~13.

3. Die is facing up for mold. Die is facing

down for trim/form, ie. reverse trim/form.

4. The footlength measuring is based on the

5. Dimensions are exclusive of mold flash

NOTE:

Y14.5M, 1982.

gauge plane method.

and gate burr.

0.05(MIN)

10 TYP.

(2 plcs)

10 TYP.

0.15(MAX)

2.90±0.100

0.950 0.950

0.350(MIN)

TYP. TYP.

(5 PLCS)

0.500(MAX)

0.45

0°~3°

10 TYP.

(2 plcs)

0.20 BSC.

Gauge Plane ±0.10

0.127 TYP

10 TYP.

(2 plcs)

Dimensions are in millimeters

MP1522 – 25V STEP-UP CONVERTER IN A SOT23-5 PACKAGE

NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications.

Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS

products into any application. MPS will not assume any legal responsibility for any said applications.

MP1522 Rev. 1.9 www.MonolithicPower.com 7

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3x3 QFN6