MAX16807(2009) 查看數據表（PDF） - Maxim Integrated

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MAX16807
(Rev.:2009)

Integrated 8-Channel LED Driver with Switch-Mode Boost and SEPIC Controller

Maxim Integrated 

Integrated 8-Channel LED Driver with

Switch-Mode Boost and SEPIC Controller

The oscillator frequency is then:

fOSC

=

1

(tC +

tD)

Reference Output

REF is a 5V reference output that can source 20mA.

Bypass REF to AGND with a 0.1µF capacitor.

Current Limit

The MAX16807 includes a fast current-limit comparator

to terminate the on cycle during an overload or a fault

condition. The current-sense resistor, RCS, connected

between the source of the external MOSFET and

AGND, sets the current limit. The CS input has a volt-

age trip level (VCS) of 0.3V. Use the following equation

to calculate RCS:

RCS

=

VCS

IP − P

IP-P is the peak current that flows through the MOSFET.

When the voltage produced by this current (through the

current-sense resistor) exceeds the current-limit com-

parator threshold, the MOSFET driver (OUT) turns the

switch off within 60ns. In most cases, a small RC filter is

required to filter out the leading-edge spike on the sense

waveform. Set the time constant of the RC filter at 50ns.

Buck-Boost (SEPIC) Operation

Figure 2 shows a buck-boost application circuit using

the MAX16807 in a stand-alone mode of operation.

SEPIC topology is necessary when the total forward

voltage of the LEDs in a string is such that VOUT can be

below or above VIN.

VIN

L1

C1

D

VOUT

COUT

Q

L2

R1

LEDs

RCS

CC2

CC1

RC1

R2

CIN

3V TO 5.5V

CBYP

EXTERNAL

CLOCK INPUT

EXTERNAL

DIM INPUT

RSET

OUT CS AGND COMP

VCC

FB

V+

MAX16807

PGND

OUT0

OUT1

DIN

OUT2

LE

OUT3

OUT4

CLK

OUT5

DOUT

OUT6

OE

OUT7

SET

REF

RTCT

RT

CREF

CT

Figure 2. Buck-Boost (SEPIC) Configuration

14 ______________________________________________________________________________________

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