TUSB422 datasheet(13/71 Pages) TI1

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TUSB422

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Table 2. USB Type-C DRP Toggle Requirements (continued)

PARAMETER

MIN

MAX

DESCRIPTION

dcSRC.DRP

30%

70%

The percent of time that DRP shall advertise Source (Rp) during tDRP .

The following steps are for initialization of the TUSB422 for DRP operation.

1. Upon TUSB422 power-up, the Power Status flag in Alert Register should get set indicating TUSB422 is

initialized. When set, this flag will cause the INT_N pin to be assert low.

2. SW read the Alert Registers to determine reason for INT_N assertion. The expectation is Power Status bit

(Reg10h bit 1) is set.

3. SW read Power Status register and notice that TCPC_INIT_STATUS flag is cleared. This indicates TUSB422

is ready.

4. SW clear Power Status bit in Alert register by writing a 1’b1 to the bit.

5. Program the TUSB422 to present Rd on both CC pins. This is done by writing 0x4A to the Role Control

6. Write Look4Connection command to the Command register.

7. The TUSB422 now presents Rd on both Rp pins and look for a connection.

The TUSB422 autonomously toggles between Rd and Rp according to the setting of the CC General Control

value before performing Step 6.

7.3.6 Type-C Current Mode Advertising

Once a valid cable detection and attach have been completed, the TUSB422 has the option to advertise thru

CC1/CC2 pins the level of Type-C current a UFP can sink. The TUSB422 supports all three possible Type-C

current options: Default (500 mA / 900 mA), Medium(1.5 A), and High (3 A). The current advertisement used by

TUSB422 is determined by the value programmed in the Role Control register.

NOTE

VDD must be greater than 3.0 V to advertise 3 A current.

7.3.7 VBUS Source Enable/Disable Control

The TUSB422 is unable to directly control VBUS enable due to no GPIO support. For this reason, external

microprocessor must directly control the Vbus enable. If it wishes, the external microprocessor may notify the

TUSB422 when Vbus has been enable/disabled, or raised above vSafe5V value. Notification to TUSB422 comes

in the form of writing to the Command register any of the following commands: SourceVbusDefaultVoltage (that

is, vSafe5V enable), SourceVbusHighVoltage (that is, greater than vSafe5V), or DisableSourceVbus. If these

commands are issued to the TUSB422, the TUSB422 ignores these commands.

7.3.8 VBUS Sink Enable/Disable Control

The TUSB422 cannot directly control VBUS Sink path, and therefore; VBUS sink path control is handled

externally. Software may write the SinkVbus command to TUSB422 Command register, but the TUSB422

ignores this command.

7.3.9 VBUS Monitoring

One of the features of USB PD is the ability to raise VBUS above the default vSafe5V level. The ability to monitor

the VBUS voltage level is critical to determining when VBUS is at desired level as well as when VBUS is no

longer present. The TUSB422 implements measuring of VBUS and the results are stored in the VBUS Voltage

Power Control register.

7.3.10 VBUS Discharge

The TUSB422 implements internal VBUS discharge. The TUSB422 can be setup to discharge VBUS

automatically based on Type-C conditions or software can force a VBUS discharge by setting the

FORCE_DISCHARGE bit in the Power Control register.

TUSB422 Datasheet(PDF) 13 Page - Texas Instruments

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