FUSB307BVMPX datasheet(18/57 Pages) ONSEMI

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FUSB307B

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USB−PD Rev 3.0 Features

Extended Data Messages

Extended Data Messages is only supported via Chunking

where large messages are broken into 2 or more 26 byte

chunks.

SinkTx

The USB−PD Rev 3.0 has added this feature to allow the

Sink to safely transmit a message reducing the risk of

collisions.

The Protocol layer in the Source will request to set the Rp

value to SinkTxOk to indicate that the Sink can initiate an

Atomic Message Sequence (AMS). The Protocol layer in the

Source will request to set the Rp value to SinkTxNG to

indicate that the Sink cannot initiate an AMS since the

Source is about to initiate an AMS.

The Sink TCPM that desires to transmit will write the TX

Buffers and SINK_TRANSMIT register. The FUSB307B

will wait for the Rp value to be set to SinkTxOk before

transmitting the message. If Rp is already set to SinkTxOk,

a SINK_TRANSMIT will transmit immediately.

In the case where the Sink TCPM wants to abort the

message transmission before the Rp value has changed to

SinkTxOk, it can write SINK_TRANSMIT.EN_SNK_TX

= 0b. If a transmission has already started, writing this

interrupt will be generated.

TXBYTECNT

less

than

when

SINK_TRANSMIT.TXSOP

<101

requested,

FAULTSTAT.I2CERR interrupt is generated.

The ALERTL.I_RXSTAT must be cleared when

SINK_TRANSMIT is written or an ALERTL.I_TX_DISC

is asserted.

Table 4. RP SETTINGS FOR SINK TX

Source Rp

Parameter

Description

Sink Operation

Source Operation

1.5 A @5 V

SinkTxNG

Sink Transmit

“No Go”

Sink cannot initiate an AMS.

Sink can only respond to

Messages as part of an AMS

Source can initiate an AMS

tSinkTx after setting Rp to this

value (Note 5)

3.0 A @5 V

SinkTxOk

Sink Transmit “OK”

Sink can initiate an AMS

Source cannot initiate an AMS

while this value is set

5. The TCPM is responsible for tSinkTx timer.

Fast Role Swap

Fast Role Swap is the process of exchanging the Source

and Sink roles between Port Partners rapidly due to the

disconnection of an external power supply.

The Fast Role Swap process is intended for use by a

PDUSB HUB that presently has an external wall supply, and

is providing power both through its downstream Ports to

USB Devices and upstream to a USB Host such as a

notebook. On removal of the external wall supply Fast Role

Swap enables a VBUS supply to be maintained by allowing

the USB Host to apply vSafe5V after having detected Fast

Role Swap signaling.

The initial Source will signal a Fast Role Swap request by

driving CC to ground with a resistance of less than

rFRSwapTx for tFRSwapTx. The initial Source shall only

signal a Fast Role Swap when it has an Explicit Contract. On

transmission of the Fast Role Swap signal any pending

Messages will be Discarded by internally toggling

PD_RESET. The Fast Role Swap signal may override any

active transmissions. Since the initial Sink’s response to the

Fast Role Swap signal is to send a FR_Swap Message, the

initial Source shall ensure Rp is set to SinkTxOk once the

Fast Role Swap signal is complete.

The flow diagram in Figure 17 demonstrates the HUB and

Host function during the initial Fast Role Swap process. The

AMS and Power Role swap necessary to complete the Fast

Role Swap is performed by the respective TCPMs.

FUSB307BVMPX Datasheet(PDF) 18 Page - ON Semiconductor

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