LM5145 datasheet(49/69 Pages) TI

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10.2.2 Design 2 – Two-Phase, 15-A, 2.1-MHz Single-Output Buck Regulator for Server Applications

Figure 10-21 shows the schematic diagram of a single-output, two-phase synchronous buck regulator with an

output voltage of 5 V and rated load current of 15 A. In this example, the target half-load and full-load efficiencies

are 93% and 91%, respectively, based on a nominal input voltage of 12 V that ranges from 5 V to 36 V. The

switching frequency is set at 2.1 MHz by resistor RRT. The 5-V output is connected to VCCX to reduce IC

bias power dissipation and improve light-load efficiency. An output voltage of 3.3 V is also feasible simply by

connecting FB1 to VDDA.

Note

See the LM5143-Q1 4-phase Buck Regulator Design for Automotive ADAS Applications application

report for a four-phase, 30-A version of this design.

VIN = 5 V...36 V

(12 V nom)

SS2 RES

DEMB

AGND SS1

COMP2

PGND2

VOUT2

CS2

LO2

SW2

HO2

HB2

VIN

COMP1

PGND1

VOUT1

CS1

LO1

SW1

HO1

HB1

VCC

PG1

HOL1

LOL1

HOL2

LOL2

EN1

EN2

VCCX

VDDA

PG2

SYNCOUT

VIN

LM25143

* VOUT tracks VIN if VIN < 5.4 V

LO1

CO2

CIN

CSS

CRES

CVDDA

LO2

CO1

RS2

RS1

RHO2

RHO1

CDITH

DITH

RRT

0.47 F

10 F

10 nF

47 F

10 nF

7 m

0.68 H

47 F

7 m

0.68 H

2.2 F

10.5 k

RCOMP

CCOMP

820 pF

30.1 k

CVCC2

2.2 F

CVCC1

CVCCX

2.2 F

VOUT = 5 V

IOUT = 15 A

DB1

0.1 F

CBST1

0.1 F

CBST2

DB2

68 nF

0.22 F

FB1

FB2 MODE

VDDA

Figure 10-21. Application Circuit 2 With LM25143 Two-Phase Buck Regulator at 2.1 MHz

10.2.2.1 Design Requirements

Table 10-4 shows the intended input, output, and performance parameters for this automotive application design

example.

Table 10-4. Design Parameters

Design Parameter

Value

Input voltage range (steady state)

5 V to 18 V

Minimum transient input voltage

5 V

Maximum transient input voltage

36 V

Output voltage

5 V

Output current

15 A

Switching frequency

2.1 MHz

Output voltage regulation

±1%

Shutdown current

4 µA

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LM25143

SNVSC10 – MARCH 2022

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