5.4

USB charging system scalability

Thanks to its simple implementation and system compliancy with both legacy USB charging and latest USB

power delivery specification, USB-C applications using TCPP01-M12 can simply migrate from legacy USB

charging (see Figure 19) to USB power delivery charging (see Figure 20) by simply swapping their STM32 from

general purpose (for example: STM32L0) to general purpose + UCPD (example: STM23G0) and remove C1/C2

and add R5/R6 in the PCB to take benefit of the USB-C power delivery. Empty PCB footprints can be planned

earlier in the design to allow this system scalability.

5.5

How to handle dead battery (DB) condition with the TCPP01-M12

Dead battery use case happens when a battery-operated sink (consumer or UFP) application has its battery fully

depleted. In this case TCPP01-M12 enters into dead battery operation.

Dead battery behavior is basically a pull down (Rd) or a voltage clamp when a USB type-C source voltage is

applied to CC. It is interpreted as a request by the sink to receive VBUS. It thus facilitates the charging of

equipment with a fully depleted battery:

•

It must be present in most cases

•

It must not be present in the case of a (pure) type-C Source, for example a wall charger

The DB/ or 'dead battery resistor management' pin is a pulled-down active-low TCPP01-M12 input. The DB/ pin

can be used in two ways:

•

The DB/ pin is connected to VCC or

•

The DB/ pin is driven by an MCU GPIO

As long as the DB/ pin is low or high-impedance (an internal 5 kΩ pull-down sets the level to ‘0’), the dead-battery

resistors are connected and CC switches are open (OFF state).

When the DB/ pin is tied to VCC, the DB/ resistors are disconnected and CC OVP switches are closed (ON state).

DB/ usage in SINK (SNK) applications:

•

After system power-up, the DB/ pin must be kept at 0. In this case Rd is enabled at TCPP01-M12 level.

•

Once Rd is enabled in the UCPD (USB-C power delivery controller), the DB/ pin must be set to the logic

level '1'

TCPP01-M12

VCC

TCPP01-M12

DB/

TCPP01-M12

DB clamp present

TCPP01-M12

CC1/CC2 OVP FET

state

TCPP01-M12

DB function state

0

0

Yes

Open

Activated

0

1

Yes

Open

Activated

1

0

Yes

Open

Activated

1

1

No

Closed

Inactivated

Note:

When STM32-UCPD boots, Rd seen on CC lines are coming from TCPP01-M12. When STM32-UCPD has

wake-up, Rd from TCPP01-M12 are disconnected and STM32-UCPD set Rd on CC lines from UCPD IP

TCPP01-M12

USB charging system scalability

DS12900 - Rev 1

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