High-Efficiency LCD Boost

with True Shutdown

_______________________________________________________________________________________

5

PIN

MAX8570

(µDFN)

MAX8570/

MAX8571/

MAX8574

(SOT23)

MAX8572/

MAX8573/

MAX8575

(SOT23)

NAME

FUNCTION

31

—

FB

Feedback for Setting the Output Voltage. Connect FB to the center of a resistor

voltage-divider from the output to GND to set positive output voltages.

—

—

1

OUT

Output. The output voltage is preset to 15V. Connect a 1µF ceramic capacitor

from OUT to GND. In shutdown, OUT is pulled to GND by an internal 7.5m

Ω

resistor.

2

2

2

GND

Ground

13

3

SHDN

Shutdown Input. A logic-low at SHDN places the part in low-power shutdown

6

4

4

LX

Inductor Switching Connection

55

5

SW

Isolation Switch Output. Internally connected to the drain of a p-channel

MOSFET used to isolate the output from the input during shutdown. Connect a

4.7µF ceramic capacitor from SW to GND. If true shutdown is not required, SW

can be left open with the input supply connected directly to the inductor.

46

6

Pin Description

LOAD TRANSIENT

MAX8570/71/73/74/75 toc15

100

µs/div

100mV/div

(AC-COUPLED)

5mA/div

0

STARTUP AND SHUTDOWN WAVEFORMS

MAX8570/71/73/74/75 toc16

400

µs/div

5V/div

10V/div

200mA/div

1.8

Ω LOAD

0

0

BOOST SOFT-START

SW TURN-ON

Typical Operating Characteristics (continued)

°C, unless otherwise noted.)