Datasheet

R
OV1
= 13.7 k:
R
OV2
= 432 k:
=
V
OFFTURN
=
-
V= 39.7
R
OV1
k7.13 :
( )
k432k7.131.24V :+:x
(
)
RR1.24V
OV2OV1
+x
V
OFFTURN-
0.5
x
0.5
x
:== k13.6
-
-
0.62VV
OFFTURN
x R1.24V
OV2
=R
OV1
:x k4321.24V
- 0.62V40V
2
9.94VA23k432A23RV
OVHYSO
=
x:
=
x
=
P
P
===
A
23
10V
R
OV2
P
:k435
V
HYSO
A23
P
LM3421, LM3421-Q1
LM3423, LM3423-Q1
www.ti.com SNVS574E –JULY 2008–REVISED MAY 2013
12. OUTPUT OVLO
Solve for R
OV2
:
(144)
The closest standard resistor is 432 kΩ therefore V
HYSO
is:
(145)
Solve for R
OV1
:
(146)
The closest standard resistor is 13.7 kΩ making V
TURN-OFF
:
(147)
The chosen components from step 12 are:
(148)
DESIGN #1 Bill of Materials
Qty Part ID Part Value Manufacturer Part Number
1 LM3421 Buck-boost controller TI LM3421MH
1 C
BYP
2.2 µF X7R 10% 16V MURATA GRM21BR71C225KA12L
1 C
CMP
0.33 µF X7R 10% 25V MURATA GRM21BR71E334KA01L
1 C
FS
0.27 µF X7R 10% 25V MURATA GRM21BR71E274KA01L
4 C
IN
4.7 µF X7R 10% 100V TDK C5750X7R2A475K
4 C
O
10 µF X7R 10% 50V TDK C4532X7R1H106K
1 C
OV
47 pF COG/NPO 5% 50V AVX 08055A470JAT2A
1 C
T
1000 pF COG/NPO 5% 50V MURATA GRM2165C1H102JA01D
1 D1 Schottky 100V 12A VISHAY 12CWQ10FNPBF
1 L1 33 µH 20% 6.3A COILCRAFT MSS1278-333MLB
1 Q1 NMOS 100V 32A FAIRCHILD FDD3682
1 Q2 PNP 150V 600 mA FAIRCHILD MMBT5401
1 R
CSH
12.4 kΩ 1% VISHAY CRCW080512K4FKEA
1 R
FS
10Ω 1% VISHAY CRCW080510R0FKEA
2 R
HSP
, R
HSN
1.0 kΩ 1% VISHAY CRCW08051K00FKEA
1 R
LIM
0.04Ω 1% 1W VISHAY WSL2512R0400FEA
1 R
OV1
13.7 kΩ 1% VISHAY CRCW080513K7FKEA
1 R
OV2
432 kΩ 1% VISHAY CRCW0805432KFKEA
1 R
SNS
0.1Ω 1% 1W VISHAY WSL2512R1000FEA
1 R
T
49.9 kΩ 1% VISHAY CRCW080549K9FKEA
1 R
UV1
18.2 kΩ 1% VISHAY CRCW080518K2FKEA
1 R
UV2
130 kΩ 1% VISHAY CRCW0805130KFKEA
Copyright © 2008–2013, Texas Instruments Incorporated Submit Documentation Feedback 45
Product Folder Links: LM3421 LM3421-Q1 LM3423 LM3423-Q1