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V
TURN-OFF
=
R11
1.24V x (0.5 x 12.4 k: + 432 k:)
12.4 k:
1.24V x (R11 + R18)
= 44V
V
TURN-OFF
=
1.24V x R18
V
TURN-OFF
± 620 mV
= 12.3 k:
R11 = =
1.24V x 432 k:
44V ± 620 mV
V
HYSO
= R18 x 23 PA = 432 k: x 23 PA = 9.9V
V
HYSO
23 PA
= 435 k:
R18 =
10V
=
23 PA
R4 = 16.9 k:
R13 = 10 k:
R5 = 1.4 k:
V
HYS
=
R5
23 PA x 16.9 k: x (1.4 k: + 10 k:)
1.4 k:
V
HYS
=
+ 23 PA x R13
23 PA x R4 x (R5 + R13)
+ 23 PA x 10 k: = 3.4V
R4 =
R5 x (V
HYS
- 23 PA x R13)
23 PA x (R5 + R13)
= 16.9 k:
R4 =
1.4 k: x (3.4V - 23 PA x 10 k:)
23 PA x (1.4 k: + 10 k:)
V
TURN-ON
=
R5
1.24V x (1.4 k: + 10 k:)
1.4 k:
1.24V x (R5 + R13)
= 10.1V
V
TURN-ON
=
1.24V x R13
V
TURN-ON
- 1.24V
= 1.42 k:
R5 = =
1.24V x 10 k:
10V - 1.24V
D1 o 12A, 100V, DPAK
Design Procedure www.ti.com
The chosen component from Section 6.11 is:
(44)
6.12 Input UVLO
Since PWM dimming will be evaluated, a three resistor network will be used. Assume R13 = 10 kΩ and
solve for R5:
(45)
The closest standard resistor is 1.4 kΩ therefore V
TURN-ON
is:
(46)
Solve for R4:
(47)
The closest standard resistor is 16.9 kΩ making V
HYS
:
(48)
The chosen components from Section 6.12 are:
(49)
6.13 Output OVLO
Solve for R18:
(50)
The closest standard resistor is 432 kΩ therefore V
HYSO
is:
(51)
Solve for R11:
(52)
The closest standard resistor is 12.4 kΩ making V
TURN-OFF
:
(53)
10
AN-2010 LM3423 Buck-Boost 2 Layer Evaluation Board SNVA415C–June 2010–Revised May 2013
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