USB334X datasheet(39/92 Pages) MICROCHIP

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DS00002646A-page 39

USB334x

The charger detection circuitry runs from the VDD33 supply and requires that the VDD33 supply to be present to run

the charger detection circuitry. The VDD33 supply is present anytime the RESETB pin is pulled high and VBAT is pres-

ent. The charger detection circuits are fully functional while in Low Power Mode (Suspendm = 0). The status of the Vdat-

Det can be relayed back to the Link through the ULPI interrupts in both Synchronous mode and Low Power Mode.

5.9.1

ACTIVE ANALOG CHARGER DETECTION (USB-IF BATTERY CHARGING 1.2)

The USB334x includes the active analog charger detection specified in the USB-IF Battery Charging Specification. The

additional analog circuitry will allow the USB334x to:

Detect a Dedicated Charging Port (DCP) with the DP and DM pins shorted together.

Detect a Standard Downstream Port (SDP) which has no battery charging circuitry.

Detect a Charging Downstream Port (CDP) which actively supplies voltage to the DM pin when connected to a

USB-IF BC 1.2 compatible device.

Behave as a Charging Downstream Port by enabling the voltage source on the DM pin.

The charger detection circuitry is shown in Figure 5-9.

The VdatDet output is qualified with the Linestate[1:0] value. If the Linestate is not equal to 00 the VdatDet signal will

not assert.

The proper detection process flows through different modes of detection and uses the linestate and VdatDet signals

values to determine the connection. Table 5-7 describes the bit values that need to be set to enter each mode.

5.9.1.1

Example Charger Detection Flow - Dedicated Charging Port

The USB-IF Battery Charging 1.2 specification describes in detail the flow for each charger type, but below is an exam-

ple of the flow used to detect a Dedicated Charger (DCP).

Device detects Vbus voltage is present from RXCMD, (SESS_VLD is 1)

Device enters the Device Connect Detect mode.

If the linestate still equals 10 after a specified timeout, the charger is an unknown charger and there will be no

attempted USB enumeration.

If the linestate equals 00 or 11, the device will go to the next mode:

TABLE 5-7:

USB CHARGER SETTING VS. MODES

Charger Detection Modes

Device Connect Detect

(The Connect Detect setting in Table 5-1 must be followed)

1001

Device Charger Detection

0000

Device Enhanced Charger Detection

0100

Device USB Operation

0000

Charging Host Port, no charging device attached and SE0

(VdatDet = 0)

0111

Charging Host Port, charging device attached (VdatDet = 1)

0111

Charging Host Port USB Operation

0111

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