,

I N

B ULK

L

LE D

OUT LED(RI P)

P

C

2

R

V

I

£

f

p

,

o

NTC(BK)

NTC(T )

BK

o

R

R

=

1

1

exp β

T

T

-

é æ

ö ù

ç

÷

ê

ú

ë è

ø û

LM3447

SNOSC65 A – APRIL 2012 – REVISED MAY 2012

www.ti.com

STEP

VARIABLE

DESCRIPTION

16

RNTC

where,

RNTC(BK) = 10.5 kΩ, is the fixed break point resistance,

TBK is the break point temperature in Kelvin,

TO is the room temperature in Kelvin,

RNTC(To) is the manufacturer specified NTC resistance at room temperature,

β is the NTC resistor characteristics specified by the manufacturer.

17

CBULK, RO

where,

ILED(RIP) is the average to peak magnitude of twice the line frequency current ripple through LED,

RLED is the dynamic resistance of the LED string,

fL is the line frequency

RO = 20 kΩ, is the recommended bleeder resistance

Spacer

REVISION HISTORY

Changes from Original (April 2012) to Revision A

Page

•

Changed the device From: Product Preview To: Production ...................................................................................... 1

24

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