STUSB4500 datasheet(13/41 Pages) STMICROELECTRONICS

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The valid VBUS voltage range is defined by a high limit VMONUSBH and a low limit that can take as value either

VTHUSB or VMONUSBL depending on system operation and VBUS voltage.

VTHUSB low limit is fixed by hardware at 3.3 V. It corresponds to the undervoltage condition to detect a VBUS

disconnection when VBUS voltage is at 5 V (USB Type-C or PDO1). The nominal value of VMONUSBL is VBUS-5%.

The low limit value can be shifted by fraction of VBUS from -1% to -15%. The nominal value of VMONUSBH is VBUS

+5%. The high limit value can be shifted independently by fraction of VBUS from +1% to +15%. It means the

threshold limits can vary from VBUS-5% to VBUS-20% for the low limit and from VBUS+5% to VBUS+20% for the

high limit.

At attachment, the valid VBUS voltage range is defined by VMONUSBH and VMONUSBL limits to establish a valid

source-to-sink connection. After attachment and during system operations, the valid VBUS voltage range is

automatically adjusted to VMONUSBH and VTHUSB limits when VBUS voltage is at 5 V (USB Type-C or PDO1), or to

VMONUSBH and VMONUSBL limits when VBUS operates under PDO2 or PDO3 voltage.

The VBUS voltage value is automatically adjusted to 5 V (USB Type-C) at attachment and to the negotiated PDO

voltage after PDO transition. During each PDO transition, the VBUS monitoring is disabled for tSrcReady (285 ms

max.) as per USB PD standard specifications. Then the new limits applicable to the negotiated PDO voltage are

monitored.

The threshold limits are preset by default in the NVM with different shift coefficients (see Section 7.3 Electrical and

timing characteristics). The threshold limits can be changed independently through NVM programming (see

Section 5 Start-up configuration).

3.4.2

VBUS discharge

The monitoring block also handles the VBUS discharge paths connected to the VBUS_VS_DISCH pin for the USB

Type-C receptacle side and to the DISCH pin for the power system side. The discharge paths are activated at the

same time when disconnection is detected, during transition to a lower PDO voltage, when a hard reset is

performed or when the device goes into the error recovery state (see Section 3.7 Hardware fault management).

At detachment, during error recovery state or hard reset, the discharge is activated for TDISUSB0V time. During

transition to a lower PDO voltage, the discharge is activated for TDISUSBPDO time.

The discharge time durations are also preset by default in the NVM (see Section 7.3 Electrical and timing

characteristics). The discharge time durations can be changed through NVM programming (see Section 5 Start-

up configuration).

The VBUS discharge feature is enabled by default in the NVM and can be disabled through NVM programming

(see Section 5 Start-up configuration).

3.4.3

VBUS power path assertion

The STUSB4500 can control the assertion of the VBUS power path from the USB Type-C receptacle, directly or

indirectly, through the VBUS_EN_SNK pin.

The table below summarizes the operating conditions that determine the electrical value of the VBUS_EN_SNK

pin during system operation.

STUSB4500

VBUS power path control

DS12499 - Rev 2

page 13/41

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