EN

LDO

S1

VREF

VBUS

VIN

VLDO

UVLO

UVLO

VIN_GOOD

VBUS_GOOD

Switch Over

Logic

S1

16

TPS66020, TPS66021

SLVSEW8 – AUGUST 2019

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Product Folder Links: TPS66020 TPS66021

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Copyright © 2019, Texas Instruments Incorporated

Power Management and Supervisory (continued)

Figure 5. Power Management and Supervisory

The VLDO terminal may be powered from either VIN or VBUS. The normal power supply input is VIN. When VIN

is present, S1 is closed and current flows from VIN to VLDO and the VBUS LDO is disabled. When VIN power is

unavailable, as in a dead battery condition, the VBUS LDO will be automatically enabled when VBUS is present,

and the VLDO terminal is powered by the VBUS LDO. The Switch Over Logic provides the decision making

capability to choose VIN or VBUS power, depending on the state of these voltages (based on their respective

UVLO comparators) and their relative levels to each other.

8.6.1.1 Supply Connections

Figure 6 shows the TPS66020 VIN being supplied from a 3.3-V supply. The VLDO output may or may not be

used to supply other circuitry in the application, for example a PD Controller. During a dead battery condition, the

internal 3.3-V VBUS LDO provides power to the TPS66020 and the VLDO output. Once VIN input supply

becomes available, the VBUS LDO is disabled and VIN provides power to the VLDO output.

The TPS66021 is well suited for 5 V only systems. VIN of the TPS66021 may be powered from an independent

supply, but in most applications it will be connected to the PP5V supply. Figure 7 shows where the VIN supply is

shared with PP5V. The VLDO output may be used optionally to supply power to external circuitry. During a dead

battery condition, the internal 5-V VBUS LDO provides power to the TPS66021 and the VLDO output. Once the

VIN input supply, in this case PP5V, becomes available, the VBUS LDO is disabled and PP5V provides power to

the VLDO output.