FUSB302BVMPX datasheet(11/32 Pages) ONSEMI

11 / 32 page

FUSB302B

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BMC POWER DELIVERY

The Type-C connector allows USB Power Delivery (PD)

to be communicated over the connected CC pin between two

ports. The communication method is the BMC Power

Delivery protocol and is used for many different reasons

with the Type-C connector. Possible uses are outlined below.

• Negotiating and controlling charging power levels

• Alternative Interfaces such as MHL, Display Port

• Vendor specific interfaces for use with custom docks or

accessories

• Role swap for dual-role ports that want to switch who is

the host or device

• Communication with USB3.1 full featured cables

The FUSB302B integrates a thin BMC PD client which

includes the BMC physical layer and packet FIFOs (48 bytes

for transmit and 80 bytes for receive) which allows packets

to be sent and received by the host software through I2C

accesses. The FUSB302B allows host software to

implement all features of USB BMC PD through writes and

reads of the FIFO and control of the FUSB302B physical

interface.

The FUSB302B uses tokens to control the transmission of

BMC PD packets

. These tokens are written to the transmit

FIFO and control how the packet is transmitted on the CC

pin. The tokens are designed to be flexible and support all

aspects of the USB PD specification. The FUSB302B

additionally enables control of the BMC transmitter through

tokens. The transmitter can be enabled or disabled by

specific token writes which allow faster packet processing

by burst writing the FIFO with all the information required

to transmit a packet.

The FUSB302B receiver stores the received data and the

received CRC in the receive FIFO when a valid packet is

received on the CC pin. The BMC receiver automatically

enables the internal oscillator when an Activity is sensed on

the CC pin and load to the FIFO when a packet is received.

The I_ACTIVITY and I_CRC_CHK interrupts alert the

host software that a valid packet was received.

Figure 12. USB BMC Power Delivery Blocks

FIFO

Code/

Control

Logic

CDR

CRC32

4B5B

BMC

CC1

CC2

Power Level Determination

The Type-C specification outlines the order of precedence

for power level determination which covers power levels

from basic USB2.0 levels to the highest levels of USB PD.

The host software is expected to follow the USB Type-C

specification for charging current priority based on feedback

from the FUSB302B detection, external BC1.2 detection

and any USB Power Delivery communication.

The FUSB302B does not integrate BC1.2 charger

detection which is assumed available in the USB transceiver

or USB charger in the system.

Power Up, Initialization and Reset

When power is first applied through VDD, the

FUSB302B is reset and registers are initialized to the default

values shown in the register map.

The FUSB302B can be reset through software by

programming the SW_RES bit in the RESET register.

If no power applied to VDD then the SRC can recognize

the FUSB302B as a SNK.

PD Automatic Receive GoodCRC

The power delivery packets require a GoodCRC

acknowledge packet to be sent for each received packet

where the calculated CRC is the correct value. This

calculation is done by the FUSB302B and triggers the

I_CRC_CHK interrupt if the CRC is good. If the

AUTO_CRC

(Switches1

bit)

set

and

AUTO_PRE = 0, then the FUSB302B will automatically

send the GoodCRC control packet in response to alleviate

the local processor from responding quickly to the received

packet. If GoodCRC is required for anything beyond SOP,

then enable SOP*.

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