USB333X datasheet(30/85 Pages) MICROCHIP

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USB333x

DS00001880A-page 30

 2009 - 2015 Microchip Technology Inc.

5.5.2

POWER ON RESET (POR)

The USB333x provides a POR circuit that generates an internal reset pulse after the VDD18 supply is stable. After the

internal POR goes high the USB333x will release from reset and begin normal ULPI operation as described in Section 5-

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

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 minimum of 1 microsecond and then high. It is not necessary to wait for the VDD33 and

VDD18

pins to discharge to 0 volts to reset the part.

The RESETB pin must be pulled high to enable the 3.3V and 1.8V regulators. A pull-down resistor is not present on the

RESETB

pin and therefore the system should drive the RESETB pin to the desired state at all times. If the system does

not need to place the USB333x into reset mode the RESETB pin should be connected to VDD18 (USB3330, USB3331,

USB3336, and USB3338) or VDDIO (USB3333).

5.5.3

RECOMMENDED POWER SUPPLY SEQUENCE

For USB operation, the USB333x requires a valid voltage on the VBAT and VDDIO pins. The VDD33 and VDD18 reg-

ulators are automatically enabled when the RESETB pin is brought high. For the USB3333, Table 5-4 presents the

power supply configurations in more detail.

The RESETB pin can be held low until the VBAT supply is stable. If the Link is not ready to interface the USB333x, the

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

Note 5-3

VDDIO

must be present for ULPI pins to tri-state.

5.5.4

START-UP

The power on default state of the USB333x is ULPI Synchronous mode. The USB333x requires the following conditions

to begin operation: the power supplies must be stable, the REFCLK must be present and the RESETB pin must be high.

After these conditions are met, the USB333x will begin ULPI operation that is described in Section 6.0.

FIGURE 5-7:

POWERING THE USB333X FROM VBUS

TABLE 5-4:

OPERATING MODE VS. POWER SUPPLY CONFIGURATION

VBAT

VDDIO

RESETB

Operating Modes Available

Powered Off

RESET Mode. (Note 5-3)

Full USB operation as described in Section 6.0, "ULPI

Operation".

VBUS

VDD33

VBAT

GND

LDO

PHY

To OTG

COUT

OVP

VBUS

To USB Con.

RVBUS

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