LM5145 datasheet(29/74 Pages) TI2

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RSS

PFM/SYNC

AGND

COMP2

VOUT2

ISNS2+

LO2

SW2

HO2

CBOOT2

VIN

COMP1

BIAS1/VOUT1

ISNS1+

LO1

SW1

HO1

CBOOT1

VCC

FB1

VDDA

FB2

SYNCOUT

CFNG

EN1

EN2

PG2

PG1

OUT2

IN1

VDDA

OUT1

CNFG

VCC

BOOT1

BOOT2

LM5137

VDDA

IN2

COMP

OUT

Figure 7-8. LM5137 Two-phase Regulator Schematic Configured for Single-output Interleaved Operation

7.3.15.3 Single-Output Multiphase Operation

A multiphase (three or four phases) regulator requires two LM5137 controllers, as illustrated in Figure 7-9.

Configure the first controller (CNTRL1) as a primary and the second controller (CNTRL2) as a secondary. To

configure the second controller, connect a 90.kΩ resistor from CNFG to AGND. This connection disables both

feedback error amplifiers of the secondary controller, placing them in a high-impedance state.

• Connect the COMP1 and COMP2 pins together on both primary and secondary controllers

• Connect SYNCOUT from the primary to PFM/SYNC of the secondary controller

• Connect the RSS pins of the both controllers

• Connect all the outputs together

• Tie FB2 (primary controller) and FB2 (secondary controller) to GND

• If PFM mode operation is required, connect FB1 of the secondary controller to PFM/SYNC of the primary

controller. Otherwise, connect FB1 to GND.

• Only PG1 of the primary is applicable. PG2 as well as the PG1/2 of the second controller can remain open

circuit or connect to GND.

The SYNCOUT of the primary controller is 90° out-of-phase and facilitates interleaved operation. RT is not used

for the oscillator when the LM5137 is in secondary mode but instead used for slope compensation. Therefore,

select the RT resistance to be the same as that of the primary. See Table 7-5.

See the Benefits of a Multiphase Buck Converter white paper and Multiphase Buck Design From Start to Finish

application report for more information.

Table 7-5. Configuration Modes for Single-Output Multiphase Operation

RCNFG

PRIMARY, SECONDARY

DRSS

INDEPENDENT OR INTERLEAVED

OUTPUTS

41.2kΩ

Primary

OFF

Interleaved

54.9kΩ

Primary

DRSS1

Interleaved

71.5kΩ

Primary

DRSS2

Interleaved

90.9kΩ

Secondary

N/A

Interleaved

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LM5137

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