LM5145 datasheet(36/66 Pages) TI2

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9.2 Typical Applications

For step-by-step design procedure, circuit schematics, bill of materials, PCB files, simulation and test results of

an LM5146-powered implementation, see TI Designs reference design library.

9.2.1 Design 1 – 12-A High-Efficiency Synchronous Buck DC/DC Regulator

Figure 9-5 shows the schematic diagram of a 5-V, 12-A buck regulator with a switching frequency of 300 kHz.

In this example, the target efficiencies are 94% and 92% at input voltages of 24 V and 48 V, respectively. The

input UVLO is set to turn on and off at 8 V and 7 V, respectively. The switching frequency is set by means

of a synchronization input signal at 300 kHz, and the free-running switching frequency (in the event that the

synchronization signal is removed) is set at 250 kHz by resistor RRT. In terms of control loop performance, the

target loop crossover frequency is 40 kHz with a phase margin greater than 50°. The output voltage soft-start

time is 6 ms.

BST

PGND

SS/TRK

COMP

AGND

IN = 8 V to 85 V

VOUT = 5 V

LM5146

VOUT

SYNC In

GND

PGOOD

SYNCOUT

SYNCIN

EN/UVLO

VIN

ILIM

PGOOD

SYNC Out

VCC

COUT

CIN

RILIM

CVCC

CBST

CSS

RFB2

RFB1

RC2

CC2

CC1

RC1

CC3

RPG

300 kHz

RRT

CILIM

3.3 H

0.1 F

10 pF

47 nF

4.7 F

RUV2

17.8 kΩ

6.8 nF

47 μF

RUV1

100 kΩ

2.2 μF

CVIN

499 Ω

0.1 μF

4.42 kΩ

23.2 kΩ

150 pF

7.5 kΩ

150 Ω

20 kΩ

40.2 kΩ

820 pF

Figure 9-5. Application Circuit 1 With LM5146 48-V to 5-V, 12-A Buck Regulator at 300 kHz

Note

This and subsequent design examples are provided herein to showcase the LM5146 controller in

several different applications. Depending on the source impedance of the input supply bus, an

electrolytic capacitor may be required at the input to ensure stability, particularly at low input voltage

and high output current operating conditions. See Section 10 for more detail.

LM5146

SNVSBV0A – JUNE 2021 – REVISED JUNE 2021

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