UPD301B/C

DS00003412A-page 22

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2020 Microchip Technology Inc.

4.3.2

DFP OPERATION

The device implements current sources to advertise current charging capabilities on both CC pins when operating as a

DFP.

When a UFP connection is established, the current driven across the CC pins creates a voltage across the UFP’s Rd

pull-down that can be detected by the integrated CC comparator. The voltages monitored are summarized in Table 4-

4. When connected to an active cable, an alternative pull-down (Ra) appears on the CC pin.

The DFP also integrates two 5V FETs for implementing the VCONN function. This is further discussed in Section 4.3.9,

"VCONN Operation".

4.3.3

RP CURRENT SOURCES

In order to advertise the current charging capabilities of the device via the integrated port power controller or external

power circuit, Rp current sources are used. The current source can be selected by software. Table 4-5 summarizes the

values supported by the current sources in regards to the programmed value.

The current source coupled with the CC pins for RP advertisement is also used for sampling the

CFG_SEL pin. When

the

CFG_SEL pin is sampled, current is steered away from the CC pins and no RP value is advertised.

4.3.4

UFP OPERATION

When operating as a UFP, the device applies an Rd pull-down on both CC lines and waits for a DFP connection from

the assertion of VBUS. The CC comparator is used to determine the advertised current charger capabilities supported

by the DFP.

4.3.5

DRP OPERATION (LEGACY)

In this configuration, software utilizes the device to alternate between a Source and Sink advertisement with an interval

of tDRP per the USB Type-C™ Specification.

TABLE 4-4:

SOURCE DETECTION

CC1

CC2

Connection State

CC Comparator State

VBUS VCONN

Open Open Nothing Attached

Monitor both CC pins for attach

Off

Off

Rd

Open UFP Attached

Monitor

CC1 for detach

On

Off

Open Rd

UFP Attached

Monitor

CC2 for detach

On

Off

Ra

Open Powered Cable, No UFP attached

Monitor

CC2 for UFP attach.

Monitor

CC1 for cable detach.

Off

Off

Open Ra

Powered Cable, No UFP attached

Monitor

CC1 for UFP attach.

Monitor

CC2 for cable detach.

Off

Off

Ra

Rd

Powered Cable, UFP attached

Monitor

CC2 for UFP detach.

CC1 is not monitored for detach.

On

On

Rd

Ra

Powered Cable, UFP attached

Monitor

CC1 for UFP detach.

CC2 is not monitored for detach.

On

On

Rd

Rd

Debug accessory mode attached

Monitor both CC pins for detach

Off

Off

Ra

Ra

Audio accessory mode attached.

Monitor both CC pins for detach

Off

Off

TABLE 4-5:

RP CURRENT SOURCES

DFP Advertisement

Current source

(1.7V to 5.5V)

RPx Value

Disabled

00b

Default USB Power

80 uA +/-20%

01b

1.5A @ 5V

180 uA +/-8%

10b

3.0A @ 5V

330 uA +/-8%

11b