EN0

VBUS

vSafe5V (max)

vSafe5V (min)

vSupply_Loss_Detect

tSrcFRSwap

EN1

PPHV Path

(old Sink)

Enabled

Disabled

Disabled

Enabled

FRS ILIMIT

Enabled

3.0A ILIMIT

PP5V Path

(new Source)

Enabled

1.5A/3.0A ILIMIT

EN0

EN1

PPHV SNK Path

Enabled

Disabled

Disabled

Enabled

FRS ILIMIT

Enabled

3.0A ILIMIT

PP5V SRC Path

Enabled

1.5A/3.0A ILIMIT

VBUS_VSAFE5V_DET

tPP5V_EN_FRS_MODE

26

TPS66020, TPS66021

SLVSEW8 – AUGUST 2019

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4. Upon EN1 = 1 assertion, the TPS6602x PPHV path is disabled automatically by the fast role swap hardware.

5. There are two cases to consider. In Case 1, as shown in Figure 17, VBUS begins to decay, while being

continuously monitored by the vSafe5V comparator circuitry that indicates when VBUS has fallen below

vSafe5V. Once this occurs, the comparator output is asserted indicating to the fast role swap hardware that it

is safe to turn on the PP5V path, and the PP5V path is enabled automatically. In Case 2, as shown in

Figure 18, VBUS may have fallen below vSafe5V, or even fully discharged to ground, so the comparator

output may already be asserted low. If so, the PP5V path shall be immediately enabled. It should be noted in

this scenario, since the VBUS capacitance has been fully discharged, a significant in-rush current will occur

when the PP5V path is enabled. Application should ensure sufficient decoupling capacitance is applied on

the PP5V supply or that the supply is designed to react to fast transient responses to avoid brown-out of the

supply rail.

6. PP5V is initially enabled with a higher current limit to ensure fast turn-on. Once fast role swap is completed,

it reverts back to the 3-A setting. The application may then choose to stay at the 3-A setting or switch to the

1.5-A setting.

Figure 16. Fast Role Swap Timing

Figure 17. Fast Role Swap Events - Case 1