USB3320 datasheet(24/70 Pages) MICROCHIP

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USB3320

DS00001792B-page 24

 2014-2015 Microchip Technology Inc.

The VBAT input must never be exposed to a voltage that exceeds VVBAT. (See Table 3-2)

5.5.2

POWER ON RESET (POR)

The USB3320 provides a POR circuit that generates an internal reset pulse after the VDD18 supply is stable. After the

internal POR goes high and the RESETB pin is high, the USB3320 will release from reset and begin normal ULPI oper-

ation as described in Section 5.5.4.

The ULPI registers will power up in their default state summarized in Table 7-1 when the 1.8V supply is brought up.

Cycling the 1.8 volt power supply will reset the ULPI registers to their default states. The RESETB pin can also be used

to reset the ULPI registers to their default state (and reset all internal state machines) by bringing the pin low for a min-

imum of 1 microsecond and then high.

The Link is not required to assert the RESETB pin. A pull-down resistor is not present on the RESETB pin and therefore

the Link must drive the RESETB pin to the desired state at all times (including system start-up) or connect the RESETB

pin to VDDIO.

5.5.3

RECOMMENDED POWER SUPPLY SEQUENCE

For USB operation the USB3320 requires the VBAT, VDD33, VDDIO and VDD18 supples. VBAT, VDD33, and VDD18

can be applied in any order. The VDD18 supply must be turned on and stable before the VDDIO supply is applied. This

does not apply in cases where the VDD18 and VDDIO supply pins are tied together.

When the VBAT supply is applied, the integrated regulator will automatically start-up and regulate VBAT to VDD33. If

the VDD33 supply is powered and the VDD18 supply is not powered, the 3.3V circuits are powered off and the VDD33

current will be limited as shown in Table 4-1.

The ULPI interface will start operating after the VDD18 and VDDIO supplies are applied and the RESETB pin is brought

high. The RESETB pin must be held low until the VDD18 and VDDIO supplies are stable. If the Link is not ready to

interface the USB3320, the Link may choose to hold the RESETB pin low until it is ready to control the ULPI interface.

FIGURE 5-8:

POWERING THE USB3320 FROM VBUS

TABLE 5-3:

OPERATING MODE VS. POWER SUPPLY CONFIGURATION

VDD33

VDD18

RESETB

Operating Modes Available

Powered Off

RESET Mode.

In this configuration the ULPI interface is available and can

be programed into all operating modes described in Section

6.0, "ULPI Operation". All USB signals will read 0.

In this mode the ULPI interface is not active and the circuits

powered from the VDD33 supply are turned off and the

current will be limited to the RESET Mode current. (Note 5-2)

VBUS

VDD33

VBAT

GND

LDO

PHY

To OTG

COUT

OVP

VBUS

To USB Con.

RVBUS

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