VBUS

VIN

VLDO

VLDO Supply

VBUS LDO

VIN switch

1

4

3

1. Device is in dead battery condition. PD

controller advertises as a Sink. Upon

connection to a Source, VBUS begins to rise.

2. VBUS LDO is selected by the power

management logic and VLDO begins to rise.

3. PD Controller negotiates a contract (may be

5V or higher) and asserts EN0 to turn on the

PPHV Sink path in order to charge the system.

4. System begins to charge and VIN begins to

rise. VIN passes its UVLO threshold.

5. If VIN supply remains above its UVLO

threshold

, VBUS LDO is disabled

and VLDO is switched over to be supplied by

VIN via switch S1.

for t

VIN_STABLE

2

5

EN0

EN1

t

VIN_STABLE

VBUS

VIN

VLDO

VLDO Supply

VIN switch

5

1

4

1. Both the VBUS and VIN supplies are

powered down. VIN supply begins to rise.

2. VLDO terminal begins to rise.

3. VLDO supplied by VIN via switch S1. VBUS

LDO remains disabled.

4. PD Controller requests Sink path to be

enabled. Since VIN supply has not been above

its UVLO threshold f

5. VIN supply remained above its UVLO

threshold

and VBUS is above its

UVLO threshold. The Sink path enables.

VBUS LDO remains disabled since VIN supply

is available.

for t

VIN_STABLE

or t

, Sink path

remains disabled. In addtion, VBUS is not

above its UVLO switch threshold, which also

keeps the Sink path disabled.

VIN_STABLE

3

EN0

EN1

t

VIN_STABLE

2

18

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 8. Normal Power Up Sequence

8.6.1.2.2

Dead Battery Operation

Figure 9 shows the typical power up sequence during a dead battery condition. During a dead battery condition,

the TPS6602x is internally powered by the VBUS LDO. The VBUS LDO may be used to supply a limited amount

of current for use in the system during dead battery, such as supplying power to a PD controller. In this case, it is

assumed the VLDO terminal is providing power to a PD controller that is controlling the TPS6602x. Once VIN is

stable, the VLDO terminal switches from being supplied by the VBUS LDO to being supplied by the VIN terminal,

and the VBUS LDO is automatically disabled. The switch over process is completely seamless.

NOTE

Switching from VBUS LDO operation to VIN operation is seamless and no device reset

will occur. When switching from VIN power to VBUS LDO operation, the switch over

circuitry will attempt to switch over to the VBUS LDO, however it is not guaranteed that the

VLDO level will be maintained above the VLDO UVLO threshold. In this case, a device

reset may or may not occur.

Figure 9. Dead Battery Power Up Sequence