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

MP1522 Rev. 1.9

www.MonolithicPower.com

3

12/9/2005

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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 100kΩ resistor in series with EN.

5

BIAS

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

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

0.5Ω 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

C1

C4

INTERNAL

POWER

ERROR

AMP

1.23V

450mA

GND

(2)

EN

(4)

BIAS

(5)

FB

(3)

SW

(1)

R2

R1

C2

C3

R3

--

+

CURRENT

--

+

GND

Figure 1—Functional Block Diagram