Datasheet

 2017 Microchip Technology Inc. DS00002245B-page 27

KSZ8041NL/RNL

3.17 Power Management

The KSZ8041NL/RNL offers the following two power management modes:

• Power Saving Mode

This mode is used to reduce power consumption when the cable is unplugged. It is in effect when the auto-negoti-

ation mode is enabled, the cable is disconnected, and register 1F bit 10 is set to 1. Under the power saving mode,

the KSZ8041NL/RNL shuts down all transceiver blocks, except for transmitter, energy detect, and PLL circuits.

Additionally, for the KSZ8041NL in MII mode, the RXC clock output is disabled. RXC clock is enabled after the

cable is connected and a link is established.

Power-saving mode is disabled by writing “0” to register 1F bit 10.

• Power-Down Mode

This mode is used to power down the entire KSZ8041NL/RNL device when it is not in use. Power down mode is

enabled by writing “1” to register 0 bit 11. In the power down state, the KSZ8041NL/RNL disables all internal func-

tions, except for the MII management interface.

3.18 Reference Clock Connection Options

A crystal or clock source, such as an oscillator, is used to provide the reference clock for the KSZ8041NL/RNL.

Figure 3-6 illustrates how to connect the 25-MHz crystal and oscillator reference clock.

FIGURE 3-6: 25-MHZ CRYSTAL/OSCILLATOR REFERENCE CLOCK

For the KSZ8041NL, Figure 3-7 illustrates how to connect the 50-MHz oscillator reference clock for RMII mode.

FIGURE 3-7: 50-MHZ OSCILLATOR REFERENCE CLOCK FOR KSZ8041NL RMII MODE

3.19 Reference Circuit for Power and Ground Connections

The KSZ8041NL/RNL is a single 3.3V supply device with a built-in 1.8V low-noise regulator. The power and ground con-

nections are shown in Figure 3-8 and Table 3-6.

25MHz OSC

+/-50ppm

22 pF

25MHz XTAL

+/-50ppm

50 M Hz OSC

+/-50 ppm

REFCLK