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TPS66020, TPS66021

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SLVSEW8 – AUGUST 2019

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Copyright © 2019, Texas Instruments Incorporated

9.2.2.2 External VLDO Capacitor (CVLDO)

For all capacitances, the DC operating voltage must be factored into the derating of ceramic capacitors.

Generally, the effective capacitance is 35-50% of the nominal capacitance with voltage applied. Assuming VLDO

= 5 V, and a minimum derated capacitance of 2.5 uF, a 10-V rated 4.7-uF capacitor is sufficient.

9.2.2.3 PP5V Power Path Capacitance

For most systems, the PP5V terminal is supplied by a DC-DC converter. Typically, the capacitance placed on the

output of the DC-DC converter is significant in order to handle current load steps. This capacitance value will be

dependent on the DC-DC converter selected. A ceramic 10 uF (X7R/X5R) 10-V rated capacitor coupled with a

0.1-uF high frequency capacitor placed, is placed as close as possible to the PP5V terminal of the TPS6602x.

This is in addition to the DC-DC converter required capacitance should be sufficient, but may need to be

adjusted based on the specific application.

It should be noted that in many Type-C/PD systems, the VCONN supply is shared with the PP5V path.

Therefore, in these systems, the application must budget the power requirements of the DC-DC converter for the

VCONN and PP5V paths combined. For this example, a minimum of 5 V at 3.3 A is required to meet the defined

system specifications.

9.2.2.4 PPHV, VBUS Power Path Capacitance

The PPHV power path is a Sink. The capacitance on the PPHV shown in and Figure 20 represents capacitance

of the charger sub-system. In a typical application, this capacitance can be in the range of 47 uF up to 100 uF,

far exceeding the 1-uF minimum specification for the TPS6602x, so no external capacitance is required to meet

this requirement in most cases. As per the PD Specification, the total capacitance on VBUS should be maximum

10 uF at connection.

The TPS6602x PPHV power path has soft start circuitry to control in-rush current when the PPHV power path is

enabled. DC loading should be minimized during soft start since the PPHV path may experience high power

dissipation especially at higher VBUS voltages. This in turn may lead to a PPHV overtemperature protection

event.

9.2.2.5 VBUS TVS Protection (Optional)

It is recommended that each VBUS port in the system have TVS protection to protect the VBUS terminal.

Inductive ringing during momentary disconnects and reconnects due to mechanical vibration or plug removal

while sinking large current loads may cause large peak voltages to be present on the VBUS terminal that may

exceed the absolute maximums of the TPS6602x. Under such events, the TVS2200 clamps the VBUS terminal

and prevents VBUS from exceeding the maximum specification. The TVS trip point should be chosen to be

safely above the normal operating ranges of the device. For this case, it is assumed VBUS voltage contracts are

less than 22-V maximum which is below the minimum breakdown voltage of the TVS2200. The maximum

clamping voltage of 28.3 V of the TVS2200 is sufficient to protect the VBUS terminal of the TPS6602x.

9.2.2.6 VBUS Schottky Diode Protection (Optional)

To prevent the possibility of large ground currents into the TPS6602x during sudden disconnects because of

inductive effects in a cable, it is recommended that a Schottky diode be placed from VBUS to GND. The

NSR20F30NXT5G or comparable device is recommended.

9.2.2.7 VBUS Overvoltage Protection (Optional)

VBUS Overvoltage Protection (OVP) is optional. If VBUS OVP is not required, then the OVP terminal should be

tied to ground as shown in Figure 3. VBUS OVP is used to detect voltages on VBUS that exceed a set threshold.

Upon detection, the PPHV power path is disabled quickly to help protect components connected downstream of

the PPHV terminal. It should be noted that VBUS OVP is not a replacement for VBUS TVS protection which is

protecting the VBUS terminal itself.

The VBUS OVP threshold is set by a resistor divider from the VBUS terminal to ground as shown in Figure 2. For

this design, R1 and R2 are fixed values to provide VBUS OVP protection at the highest voltage contract level.

Using R1 = 432-kΩ and R2 =20-kΩ sets a nominal VBUS OVP threshold of 22.6 V. For some applications, it may

be desirable to dynamically change the VBUS OVP level based on the negotiated power contract. One possible

way is shown in Figure 4. In this case, the PD controller via GPIO, selects the proper divider ratio to set the

VBUS OVP threshold based on the negotiated voltage contract level.