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8.3.4.3 Buck Regulator with External LDO

The buck regulator also supports the voltage requirement to fed to external LDO to generate standard 3.3 V or

5.0 V output rail with higher accuracies. The buck output voltage should be configured to 4 V or 5.5 V to provide

for a extra headroom to support the external LDO for generating 3.3 V or 5 V rail as shown in Figure 8-11.

This allows for a lower-voltage LDO design to save cost and better thermal management due to low drop-out

voltage.

LBK

SW_BK

GND_BK

Control

CBK

VBK

(4V / 5.7V)

FB_BK

3.3V / 5V

LDO

VIN

GND

VLDO

CLDO

GND

Ext. Load

VLDO

(3.3V / 5V)

External LDO

Figure 8-11. Buck Regulator with External LDO

8.3.4.4 AVDD Power Sequencing on Buck Regulator

The AVDD LDO has an option of using the power supply from mixed mode buck regulator to reduce power

dissipation internally. The power sequencing mode allows on-the-fly changeover of LDO power supply from DC

mains (VM) to buck output (VBK) as shown in Figure 8-12. This sequencing can be configured through the

BUCK_PS_DIS bit . Power sequencing is supported only when buck output voltage is set to 5.0 V or 5.7 V.

MCT8316Z-Q1

SLVSGO3 – DECEMBER 2021

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MCT8316Z Datasheet(PDF) 28 Page - Texas Instruments