=
V
1
.
10
k
98
.
6
:
(
)
k
9
.
49
k
98
.
6
V
24
.
1
:
+
:
x
V
ON
TURN
=
-
V
ON
TURN
=
-
V
24
.
1
(
)
R8
R7+
x
R7
=
:
=
k
06
.
7
:
x
k
9
.
49
V
24
.
1
-
V
24
.
1
V
10
=
R7
x
R8
V
24
.
1
-
-
V
24
.
1
V
ON
TURN
1
k
9
.
49
A
22
R8
V
HYS
x
:
=
P
x
=
V
1
.
A
22
=
P
=
=
V
R8
HYS
=
:
k
50
P
A
22
P
A
22
V
1
.
1
SMC
,
V
100
,
A
3
D1
o
mA
147
V
D
x
=
x
mV
750
=
mW
110
I
P
D
D
=
(
)
1
I
D
1
I
LED
D
-
=
x
-
=
¨¨
©
§
I
LED
x
¸¸
¹
·
V
IN
K
x
V
O
mA
147
A
5
.
1
=
x
¸¸
¹
·
V
42
1
I
D
-
=
¨¨
©
§
97
.
0
V
48 x
V
V
MAX
IN
MAX
D
=
=
-
-
V
75
Q1
o
3.8
DPAK
,
V
100
,
A
mW
387
m
190
A
43
.
1
R
I
P
2
DSON
2
RMS
T
T
=
:
x
=
x
=
-
1
1.5A
x
+
x
x
=
¨
¨
©
§
V
42
12
1
97
.
0
V
48 x
I
RMS
T-
2
¸
¸
¹
·
¸¸
¹
·
¨¨
©
§
308mA
1.5A
1.43A
=
I
RMS
T-
I
LED
x
=
1
D
2
x
+
x
¸¸
¸
¹
·
¸
¸
¹
·
¨
¨
©
§
¨¨
¨
©
§
12
1
i
L-PP
'
I
LED
I
RMS
T-
=
A
35
.
1
=
A
5
.
1
V
42 x
97
.
0
V
48 x
I
D
I
LED
T
=
x
=
V
IN
K
x
I
V
LED
O
x
V
75
V
V
MAX
IN
MAX
T
=
=
-
-
www.ti.com
Design Procedure
6.7
P-Channel MOSFET
Determine minimum Q1 voltage rating and current rating:
(18)
(19)
A 100V 3.8A PFET is chosen with R
DS-ON
= 190m
Ω
and Q
g
= 20nC. Determine I
T-RMS
and P
T
:
(20)
(21)
The chosen component from step 6 is:
(22)
6.8
Recirculating Diode
Determine minimum D1 voltage rating and current rating:
(23)
(24)
A 100V 3A diode is chosen with V
D
= 750mV. Determine P
D
:
(25)
The chosen component from step 7 is:
(26)
6.9
Input Under-Voltage Lockout (UVLO)
Solve for R8:
(27)
The closest 1% tolerance resistor is 49.9 k
Ω
so V
HYS
is:
(28)
Solve for R7:
(29)
The closest 1% tolerance resistor is 6.98 k
Ω
so V
TURN-ON
is:
(30)
7
SNVA390D – May 2009 – Revised May 2013
AN-1953 LM3409HV Evaluation Board
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