Texas Instruments LM3423 Evaluation Board LM3423BBLSCSEV/NOPB LM3423BBLSCSEV/NOPB Datenbogen
Produktcode
LM3423BBLSCSEV/NOPB
V
91
V
21
V
70
V
V
V
O
MAX
IN
MAX
T
=
+
=
+
=
-
-
C
IN
= 4 x 4.7
P
F
x
A
1
=
I
LED
I
RMS
IN-
=
1- 0.677
677
.
0
1.45A
x
1- D
MAX
D
MAX
=
C
IN
=
=
kHz
504
mV
100
x
467
.
0
A
1 x
F
27
.
9
P
=
f
'
v
SW
PP
IN-
x
D
I
LED
x
F
27
.
0
C
FS
P
=
F
0.33
C
CMP
P
=
:
10
R
FS
=
1
=
F
28
.
0
1
P
=
=
C
FS
10
:
x
sec
rad
k
360
10
:
3
P
Z
x
Z
P3
= (max
Z
P1
,
Z
Z1
) x 10 =
Z
Z1
x 10
Z
P3
= 36k
sec
rad
x 10 = 360k
sec
rad
F
30
.
0
1
1
C
CMP
P
=
=
=
675
.
0
e
5
sec
rad
6
x
:
e
5
6
2
P
x
Z
:
=
=
sec
rad
675
.
0
=
sec
rad
k
19
min(
Z
P1
,
Z
Z1
)
Z
P2
=
5 x T
U0
Z
P1
5 x 5630
5 x 5630
=
T
0
U
=
5630
=
04
.
0
A
1
467
.
1
:
x
x
V
620
533
.
0
x
(
)
D
1+
R
I
LIM
LED
x
x
V
620
D
x
c
SNVS574E – JULY 2008 – REVISED MAY 2013
(121)
To ensure stability, calculate
ω
P2
:
(122)
Solve for C
CMP
:
(123)
To attenuate switching noise, calculate
ω
P3
:
(124)
Assume R
FS
= 10
Ω
and solve for C
FS
:
(125)
The chosen components from step 7 are:
(126)
8. INPUT CAPACITANCE
Solve for the minimum C
IN
:
(127)
To minimize power supply interaction a 200% larger capacitance of approximately 20 µF is used, therefore the
actual
actual
Δ
v
IN-PP
is much lower. Since high voltage ceramic capacitor selection is limited, four 4.7 µF X7R capacitors
are chosen.
Determine minimum allowable RMS current rating:
(128)
The chosen components from step 8 are:
(129)
9. NFET
Determine minimum Q1 voltage rating and current rating:
(130)
Copyright © 2008–2013, Texas Instruments Incorporated
43
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