SNVA991 October   2022 LM5123-Q1

 

  1.   How to Design a Boost Converter Using LM5123
  2.   Trademarks
  3. 1Design Example
  4. 2Calculations and Component Selection
    1. 2.1  Switching Frequency
    2. 2.2  Initial Inductor Calculation
    3. 2.3  Current Sense Resistor Selection
    4. 2.4  Inductor Selection
    5. 2.5  Output Capacitor Selection
    6. 2.6  Input Capacitor Selection
    7. 2.7  Feedback Resistor Selection
    8. 2.8  UVLO Resistor Selection
    9. 2.9  Soft-Start Capacitor Selection
    10. 2.10 Control Loop Compensation
      1. 2.10.1 Crossover Frequency (fcross) Selection
      2. 2.10.2 RCOMP Selection
      3. 2.10.3 CCOMP Selection
      4. 2.10.4 CHF Selection
    11. 2.11 MOSFET selection
  5. 3Implementation Results
  6. 4Small Signal Frequency Modeling
    1. 4.1 Boost Regulator Modulator Modeling
    2. 4.2 Compensation Modeling
    3. 4.3 Open Loop Modeling
  7. 5Resources

3 Implementation Results

Please see the LM5123EVM-BST User's Guide for more testing results.

Figure 3-1 Efficiency VLOAD = 24 V
Figure 3-3 Load Transient VLOAD = 24V, VSUPPLY = 8 V
Figure 3-5 35V Loop
Figure 3-2 Efficiency VLOAD = 35 V
Figure 3-4 Load Transient VLOAD = 35 V, VSUPPLY = 8 V
Figure 3-6 24V Loop
Figure 3-7 LM5123EVM-BST Schematic
Table 3-1 List of Materials
Reference Designator QTY. Specification Manufacturer Part Number

C2

 1 Cap Aluminum Polymer 120uF 50VDC 20% (8 X 12mm) SMD 0.025 Ohm 2100mA 4000h 135C Automotive T/R Nichicon PCH1H121MCL2GS
C3, C4, C5, C30, C31, C32

6

 150µF 50V Aluminum - Polymer Capacitors 17mOhm 4000 hrs @ 125°C Panasonic EEH-ZS1H151P
C6 1 CAP, CERM, 1000 pF, 50 V, +/- 10%, X7R, 0603 Kemet C0603X102K5RACTU

C7

 1 CAP, CERM, 0.1 uF, 50 V, ±10%, X7R, 0603 TDK C1608X7R1H104K080AA
C8, C14

2

 CAP, CERM, 0.01 µF, 100 V,+/- 10%, X7R, 0603 Wurth Elektronik 8.85012E+11
C9, C10, C11, C12, C13, C15, C16, C17, C18

9

 CAP, CERM, 10 uF, 50 V, +/- 10%, X7R, 1210 MuRata GRM32ER71H106KA12L
C19, C20, C21, C22, C23, C35, C36

7

 CAP, CERM, 0.1 uF, 100 V,+/- 10%, X7R, AEC-Q200 Grade 1, 0603 MuRata GCJ188R72A104KA01D
C20, C21, C22

3

 CAP, CERM, 4.7 uF, 100 V, ±10%, X7S, AEC-Q200 Grade 1, 1210 TDK CGA6M3X7S2A475K200AB
C24, C25, C26, C33

4

 CAP, CERM, 4.7 uF, 100 V, +/- 10%, X7S, AEC-Q200 Grade 1, 1210

TDK

 CGA6M3X7S2A475K200AB
C27 1 CAP, CERM, 100 pF, 50 V, +/- 5%, C0G/NP0, AEC-Q200 Grade 0, 0603

TDK

 CGA3E2NP01H101J080AA
C37 1 CAP, CERM, 100 pF, 50 V,+/- 1%, C0G/NP0, 0603 Kemet C0603X103K5RACTU
C38 1 CAP, CERM, 0.33 uF, 10 V, +/- 10%, X5R, 0603 Kemet C0603C334K8PACTU
C39, C40

2

 CAP, CERM, 0.22 uF, 50 V, +/- 10%, X7R, AEC-Q200 Grade 1, 0603

TDK

 CGA3E3X7R1H224K080AB
C41, C42

2

 CAP, CERM, 6800 pF, 50 V,+/- 5%, C0G/ NP0, 0603 MuRata GRM1885C1H682JA01D
C43 1 CAP, CERM, 47 pF, 100 V,+/- 5%, C0G/NP0, AEC-Q200 Grade 1, 0603 Kemet C0603C470J1GACAUTO
C44 1 CAP, CERM, 4.7 uF, 16 V, +/- 10%, X6S, 0603

TDK

 C1608X6S1C475K080AC
C45 1 CAP, CERM, 470 pF, 50 V, +/- 5%, C0G/NP0, 0603

AVX

 06035A471JAT2A
D1 1 Diode Schottky 60 V 1A Surface Mount SOD-123

Nexperia

 PMEG6010CEGWX
H1, H2, H3, H4

4

 Machine Screw, Round, #4-40 x 1/4, Nylon, Philips panhead

B&F Fastener Supply

 NY PMS 440 0025 PH
H5, H6, H7, H8

4

 Hex Standoff Threaded #4-40 Nylon 0.750" (19.05mm) 3/4" Natural

Keystone Electronics

 1902D_Ndrill
J1, J2, J3, J4

4

 TERMINAL SCREW PC 30AMP, TH Keystone 8199
J5, J6

2

 TEST POINT SLOTTED .118", TH

Keystone

 1040
J7, J12, J13, J14

4

 Header, 2.54 mm, 3x1, Gold, TH

Wurth Elektronik

 61300311121
J8

1

 Header, 100mil, 7x1, Gold, TH

Samtec

 TSW-107-07-G-S
J9, J10, J11

3

 Header, 2.54 mm, 2x1, Gold, TH

Wurth Elektronik

 61300211121
L1

1

 Inductor, Shielded Drum Core, WESuperflux200, 2.6 uH, 31.5 A, 0.0016 ohm, SMD

Wurth Elektronik

 7443556260
Q1, Q2, Q3, Q4

4

 MOSFET, N-CH, 60 V, 71 A, SO-8FL

ON Semiconductor

 NTMFS5C670NLT1G
R2, R3

2

 RES, 0.003, 1%, 3 W, AEC-Q200 Grade 0, 2512 WIDE

Susumu Co Ltd

 KRL6432E-M-R003-F-T1
R4, R5, R7, R8, R9, R10, R11, R16

8

 RES, 0, 5%, 0.1 W, AEC-Q200 Grade 0, 0603

Panasonic

 ERJ-3GEY0R00V
R6

1

 RES, 100, 1%, 0.1 W, 0603

Yageo

 RC0603FR-07100RL
R12

1

 RES, 0, 5%, 0.1 W, 0603

Yageo

 RC0603JR-070RL
R14

1

 RES, 100 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Vishay-Dale

 CRCW0603100KFKEA
R15

1

 RES, 86.6 k, 1%, 0.1 W, 0603

Yageo

 RC0603FR-0786K6L
R17

1

 RES, 1.00 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Vishay-Dale

 CRCW06031K00FKEA
R19, R20

2

 RES, 80.6 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Vishay-Dale

 CRCW060321K0FKEA
R21

1

 RES, 18.7 k, 1%, 0.1 W, 0603

Yageo

 RT0603DRE0714KL

R22

1

 RES, 49.9 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Panasonic

 ERJ-3EKF4992V

R23

1

 RES, 54.9 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Vishay-Dale

 CRCW060354K9FKEA

R24

1

 RES, 21.0 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Vishay-Dale

 CRCW060321K0FKEA

R26

1

 RES, 14.0 k, 0.5%, 0.1 W, 0603

Yageo America

 RT0603DRE0714KL
SH-J1, SH-J2, SH-J3, SH-J4

4

 Single Operation 2.54mm Pitch Open Top Jumper Socket

Harwin

 M7582-05
TP1, TP2, TP6, TP8

4

 Test Point, Miniature, Red, TH

Keystone

 5000
TP3

1

 Test Point, Miniature, SMT

Keystone

 5015
TP4, TP5, TP7, TP9

4

 Test Point, Miniature, Black, TH

Keystone

 5001
U1

1

 2.2-MHz Wide VIN Low-IQ Synchronous Boost Controller with Tracking

Texas Instruments

 LM5123QRGRRQ1
C1

0

 CAP, CERM, 2200 pF, 100 V, +/- 10%, X7R, 0603

MuRata

 GRM188R72A222KA01D
C28, C29

0

 CAP, CERM, 0.1 uF, 100 V,+/- 10%, X7R, AEC-Q200 Grade 1, 0603

MuRata

 GCJ188R72A104KA01D
C34

0

 CAP, CERM, 0.1 uF, 50 V, +/- 10%, X7R, 0603

TDK

 C1608X7R1H104K080AA
FID1, FID2, FID3, FID4, FID5, FID6

0

 Fiducial mark. There is nothing to buy or mount.

N/A

 N/A
L2

0

 Inductor, Shielded, Composite, 2 uH, 39.9 A, 0.001909 ohm, SMD

Coilcraft

 XAL1580-202MEB
R1

0

 RES, 2.00, 1%, 0.5 W, AEC-Q200 Grade 0, 1210

Panasonic

 ERJ-14BQF2R0U
R13

0

 RES, 100 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Vishay-Dale

 CRCW0603100KFKEA
R18

0

 RES, 80.6 k, 1%, 0.1 W, AEC-Q200 Grade 0, 0603

Vishay-Dale

 CRCW060380K6FKEA
R25

0

 RES, 24.9 k, 0.1%, 0.1 W, 0603

Yageo America

 RT0603BRD0724K9L