LM25145 datasheet(42/70 Pages) TI

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9.2.2 Design 2 – High Efficiency 48-V to 12-V 400-kHz Synchronous Buck Regulator

Figure 9-17 shows the schematic diagram of a single-output synchronous buck regulator with an output voltage

of 12 V and a rated load current of 8 A. In this example, the target half-load and full-load efficiencies are 95%

and 94%, respectively, based on a nominal input voltage of 48 V that ranges from 12.5 V to 72 V. The switching

frequency is set at 400 kHz by resistor RRT

LM5148

PFM/SYNC

CNFG

PG/SYNCOUT

AGND

VDDA

PGND

VOUT

ISNS+

CBOOT

VIN

VCC

VCCX

EXTCOMP

VOUT = 12 V

IOUT = 8 A

* VOUT tracks VIN if VIN < 12.5 V

RRT

CVDDA

CVCC

CBOOT

CIN

22 F

5 m

6.8 H

0.1 F

2.2 F

VIN = 12.5 V...72 V

54.9 k

0.1 F

RFB

48.7 k

RCNFG

41.2 k

RCOMP

4.75 k

CHF

100 pF

CCOMP

6.8 nF

VDDA

4.7 µF

Tie to VOUT

or GND

Tie to VDDA

or GND

Figure 9-17. Application Circuit 2 With LM5148 Buck Regulator Switching at 400 kHz

9.2.2.1 Design Requirements

Table 9-4 shows the intended input, output, and performance parameters for this design example. Reference the

LM5149-Q1EVM-400 evaluation module.

Table 9-4. Design Parameters

DESIGN PARAMETER

VALUE

Input voltage range (steady-state)

15 V to 72 V

Min transient input voltage

12.5 V

Max transient input voltage

80 V

Output voltage

12 V

Output current

8 A

Switching frequency

400 kHz

Output voltage regulation

±1%

No-load standby current

12 µA

Shutdown current

2.3 µA

Soft-start time

3 ms

LM5148

SNVSC01 – FEBRUARY 2023

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