LAN8804SLASHZMXC1 datasheet(26/91 Pages) MICROCHIP

26 / 91 page

LAN8804

DS00003591G-page 26

4.0

DEVICE CONNECTIONS

The following example device connection information and diagrams are included in this section:

• Voltage Regulator and Power Connections

• QSGMII MAC Interface

• Ethernet Media Interface

4.1

Voltage Regulator and Power Connections

The LAN8804 integrates an optional LDO controller for use with an external P-channel MOSFET to generate the 1.1V

supply from an existing 2.5V or 3.3V source. Use of the LDO controller and MOSFET is not required. An external 1.1V

supply can be alternatively utilized.

4.1.1

MOSFET SELECTION

The selected MOSFET should exceed the following minimum requirements:

• P-channel

• 500 mA (continuous current)

• 3.3V or 2.5V (source – input voltage)

• 1.1V (drain – output voltage)

The VGS for the MOSFET must be operating in the constant current saturated region and not towards the threshold

voltage for the cut-off region of the MOSFET, VGS(th).

A 220 µF electrolytic capacitor between 1.1V and ground is required for proper LDO operation.

4.1.2

LDO DISABLE

The LDO controller is enabled by default. It may alternatively be disabled via internal register settings. An external

source of 1.1V is necessary if the LDO is disabled.

4.1.3

POWER CONNECTIONS

Figure 4-1 illustrates the device power connections.

LAN8804/ZMXC1 Datasheet(PDF) 26 Page - Microchip Technology