UPD360 datasheet(172/221 Pages) MICROCHIP

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UPD360

DS00002084C-page 172

 2016-2017 Microchip Technology Inc.

12.2.2

OVER-VOLTAGE DETECTION LOCKOUT ON VS

The port power switch will be disabled if the voltage on the VS pin exceeds a voltage VS_OV for longer than the specified

time tMASK (5 ms). This will cause the device to enter the Error state.

12.2.3

PWR_EN INPUT (UPD360-A/UPD360-B ONLY)

In standalone DFP mode, the PWR_EN pin enables the port power switch to be turned on if conditions are met. The

port power switch cannot be closed if PWR_EN is disabled. However, if PWR_EN is enabled, the port power switch is

not necessarily closed (see Section 12.1.2, "Active State Operation"). The PWR_EN pin state will be ignored by the PPC

if the PIN_IGNORE configuration bit is set. Otherwise, the PWR_EN_SET configuration bit is checked along with the

PWR_EN pin.

12.3

USB Port Power Switch

To assure compliance to USB Type-CTM, the PPC contains a USB port power switch that supports trip current limiting

mode.

The current limit (ILIM) is set via the PWR_CAP0 and PWR_CAP1 pins (UPD360-A/UPD360-B only), and may also be

updated via the PPC Current Limit Register (PPC_CURRENT_LIMIT). The switch also includes soft start circuitry and

a separate short circuit current limit. The port power switch is on in the Active state (except when VBUS is discharging).

12.3.1

CURRENT LIMITING

The current limit (ILIM) is set via the PWR_CAP0 and PWR_CAP1 pins (UPD360-A/UPD360-B only). These pins are

read at device power-up. The current limit can be changed via the PPC Current Limit Register (PPC_CURRENT_LIMIT)

after power-up. However, the programmed current limit cannot exceed the hardware set current limit defined by the

PWR_CAP0 and PWR_CAP1 pins.

The UPD360 is pre-configured with appropriate settings to satisfy the USB Type-C™ current limiting requirements and

no register writes are necessary to use this internal 5V port power controller, when operating in standalone mode.

12.3.1.1

Short Circuit Output Current Limiting

Short circuit current limiting occurs when the output current is above the selectable current limit (PPC Current Limit Reg-

ister (PPC_CURRENT_LIMIT)). This event will be detected and the current will immediately be limited within the

tSHORT_LIM time. If the condition remains, the port power switch will flag an Error condition and enter the Error state.

12.3.1.2

Soft Start

When the PWR_EN control (UPD360-A/UPD360-B only) changes states to enable the port power switch, the PPC

invokes a soft start routine for the duration of the VBUS rise time (tR_BUS). This soft start routine will limit current flow

from VS into VBUS while it is active. This circuitry will prevent current spikes due to a step in the portable device current

draw.

In the case when a portable device is attached while the PWR_EN pin is already enabled (in standalone DFP mode), or

the PWR_EN_SET bit is enabled, if the bus current exceeds ILIM, the PPC current limiter will respond within a specified

time (tSHORT_LIM) and will operate normally at this point. The CBUS capacitor will deliver the extra current, if any, as

required by the load change.

12.3.1.3

Current Limiting Modes

The PPC current limiting operates in trip mode. This mode is active when the port power switch is closed. When oper-

ating in the Detect power state, the current capacity at VBUS is limited to IBUS_BYP”.

12.3.1.3.1

Trip Mode

When using trip current limiting, the PPC USB port power switch functions as a low resistance switch and rapidly turns

off if the current limit is exceeded. While operating using trip current limiting, the VBUS output voltage will be held rela-

tively constant (equal to the VS voltage minus the RON_PSW * IBUS current) for all current values up to the ILIM. If the

internal temperature exceeds tTSD threshold, the port power switch will open.

If the current drawn by a portable device exceeds ILIM, the following occurs:

Note:

If a load that draws between 2 mA and 7 mA is connected to the port power switch, a voltage ripple between

40-90 mVPP is observed at the VBUS output. This behavior is normal and it does not affect the charging

process when a portable device is connected.

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