LM5145 datasheet(40/62 Pages) TI

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9.2.2 Design 2 – High Density, 12-V, 8-A Rail From 48-V Automotive Battery Power

Figure 9-16 shows the schematic diagram of a 400-kHz, 12-V output, 8-A synchronous buck regulator intended

for 48-V automotive battery applications.

BST

PGND

SS/TRK

COMP

AGND

VIN = 14 V to 75 V

VOUT = 12 V

LM5145-Q1

VOUT

SYNC In

GND

SYNCOUT

SYNCIN

EN/UVLO

VIN

ILIM

PGOOD

SYNC Out

VCC

COUT

CIN

RILIM

CVCC

CBST

CSS

RFB2

RFB1

RC2

CC2

CC1

RC1

CC3

RRT

CILIM

6.8 H

0.1 F

10 pF

47 nF

2.2 F

RUV2

9.31 kΩ

4.7 nF

22 μF

RUV1

100 kΩ

2.2 μF

CVIN

619 Ω

0.1 μF

1.5 kΩ

21 kΩ

100 pF

8.06 kΩ

100 Ω

24.9 kΩ

1 nF

RBST

2.2 Ω

optional

PGOOD

RVIN

2.2 Ω

Figure 9-16. Application Circuit 2 With LM5145-Q1 48-V to 12-A Synchronous Buck Regulator at 400 kHz

9.2.2.1 Design Requirements

The required input, output, and performance parameters for this application example are shown in Table 9-7.

Table 9-7. Design Parameters

DESIGN PARAMETER

VALUE

Input voltage range (steady state)

14 V to 72 V

Input transient voltage (peak)

75 V

Output voltage and current

12 V, 8 A

Input UVLO thresholds

14 V on, 13 V off

Switching frequency

400 kHz

Output voltage regulation

±1%

Load transient peak voltage deviation, 4-A load step

< 120 mV

9.2.2.2 Detailed Design Procedure

A high power density, high-efficiency regulator solution uses automotive grade 100-V power MOSFETs in SON

5-mm × 6-mm packages, together with a low-DCR inductor and all-ceramic capacitor design. The design

occupies a footprint of 30 mm × 15 mm on a single-sided PCB. The overcurrent (OC) setpoint in this design is

set at 12 A based on the resistor RILIM and the 10-mΩ RDS(on) of the low-side MOSFET (typical at TJ = 25°C and

LM5145-Q1

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