User manual

= 9.9 k:
R15 =
V
O
x R10 x R9
R15 =
1.5e
13
x L1
35V x 14.3 k: x 0.1:
1.5e
13
x 33 PH
R6 = 0.04:
=
0.04:
= 6.13A
I
LIM
=
R6
245 mV 245 mV
=
6A
= 0.041:
R6 =
I
LIM
245 mV 245 mV
C4 = C6 = C17 = C19 = 10 PF
x
A1
=
I
LED
I
RMSCO-
=
1- 0.677
677.0
1.45A
x
1- D
MAX
D
MAX
=
DI
LED
x
=
'i
PP-LED
SW
fxr
D
x
C
O
2
= =
kHz04595.1 xx:
1 mA
467.0A1 x
F40P
'i
PP-LED
f
'i
r
SWPP-LEDD
xx
DI
LED
x
C
O
=
2
= F39.6 P=
kHz045mA195.1 xx:
467.0A1 x
C
O
H331L P
=
A89.1
12
1
1
I
RMSL
=
+
x
=
-
I
I
LED
RMSL
x
=
-
12
1
1
2
x
+
¸
¸
¹
·
¨
¨
©
§
Di
PPL
c
x
'
-
I
LED
D
c
533.0mA674
2
x
¸
¸
¹
·
¨
¨
©
§
A1
x
533.0
A1
Design Procedure www.ti.com
Determine minimum allowable RMS current rating:
(18)
The chosen component from step 5 is:
(19)
8.7 Output Capacitance
Solve for C
O
:
(20)
The closest capacitance totals 40 µF therefore Δi
LED-PP
is:
(21)
Determine minimum allowable RMS current rating:
(22)
The chosen components from step 6 are:
(23)
8.8 Peak Current Limit
Solve for R
LIM
:
(24)
The closest standard resistor is 0.04 Ω therefore I
LIM
is:
(25)
The chosen component from step 7 is:
(26)
8.9 Slope Compensation
Solve for R
SLP
:
(27)
The chosen component from step 8 is:
10
AN-1967 LM3424 Buck-Boost Evaluation Board SNVA397A–August 2009–Revised May 2013
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