Detailed Description

Boost Converter

The MAX8607 includes a fixed-frequency, PWM boost

converter that supplies the LED current. The output

voltage is adaptively controlled to provide adequate

headroom with varying LED forward voltage. The boost

converter switches an internal power MOSFET and syn-

chronous rectifier at a constant 1MHz frequency with

varying duty cycle up to 75% to maintain constant LED

current over the 2.7V to 5.5V input range. Internal spe-

cial circuits prevent any unwanted subharmonic switch-

ing in the critical buck/boost region.

LDO Current Regulator (LED)

A low-dropout (LDO) linear current regulator from LED

to LGND sinks current from the external LED’s cathode

terminal. The LED current is regulated to a user-pro-

grammable level. In movie mode, the current into LED

is regulated to 1200 times the current set by the MOV

regulated to 5000 times the current set by the FLSH

regulated to 80mA.

1MHz PWM Boost Converter for 1.5A

White LED Camera Flash

6

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LX

PGND

COMP

EN1

EN2

FLSH

MOV

GND

FORCED-PWM

BOOST CONTROL

OUTS

OUT

REF

SHUTDOWN AND

MODE CONTROL

1MHz

CLOCK

FEEDBACK

SELECT

LDO

REGULATOR

LED

LGND

1.25V

MAX8607

Figure 1. Functional Diagram