Rainbow-electronics MAX16834 Bedienungsanleitung PDF herunterladen (Seite 13)

MAX16834

High-Power LED Driver with Integrated High-Side LED

Current Sense and PWM Dimming MOSFET Driver

______________________________________________________________________________________ 13

ESR and the bulk capacitance are equal, allowing 50%

of the ripple for the bulk capacitance. The capacitance

is given by:

where I

LED

is in amperes, C

OUT

is in farads, f

is in

hertz, and ∆V

OUTRIPPLE

is in volts. The remaining 50%

of allowable ripple is for the ESR of the output capaci-

tor. Based on this, the ESR of the output capacitor is

given by:

where IL

is the peak inductor current in amperes.

Use the below equation to calculate the RMS current

rating of the output capacitor:

Input Capacitor

The input filter capacitor bypasses the ripple current

drawn by the converter and reduces the amplitude of

high-frequency current conducted to the input supply.

The ESR, ESL, and the bulk capacitance of the input

capacitor contribute to the input ripple. Use a low-ESR

input capacitor that can handle the maximum input

RMS ripple current from the converter.

For the boost configuration, the input current is the

same as the inductor current. For buck-boost

(IL (1 D )) D

COUT(RMS)

AVG MAX

MAX

××

(

VVG

××DD

MAX MAX

)( )

ESR

COUT

OUTRIPPLE

∆Ω()

()2

OUT

LED MAX

OUTRIPPLE SW

≥

××

∆

NDRV

OFF

PWMDIM

SGND

R10

MAX16834

DIMOUT

SENSE+

OVP+

CLV

COMP

PGND

UVEN

RT/SYNC

REF

REFI

FLT

LED+

LEDs

LED-

Figure 3. Buck-Boost LED Driver (V

LED+

< 28V)

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 21 22

MAX16834 1

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