Datasheet

ENC424J600/624J600
DS39935C-page 138  2010 Microchip Technology Inc.
A device in Energy Detect Power-Down mode does not
transmit link pulses, but passively listens for the remote
link partner to transmit a signal in order to wake the
device. If the remote device is also in a similar Passive
Listening mode, neither device will wake-up. This
should not cause problems for normal Ethernet
equipment, such as switches and routers, but may
raise concerns if two embedded devices using this
feature will be connected directly.
16.3 External Power-Down
For applications that are extremely power-sensitive
and have no need for memory or register retention, it
may be useful to control the device using an external
power-down circuit. This allows the host controller to
completely remove power from the device. External
power-down circuitry can be designed with either a
MOSFET on the power supply pins, or by using a
regulator with output enable capabilities.
Keep in mind that an externally controlled power-
down will require the ENCX24J600 to be completely
re-initialized, as described in
Section 8.0 “Initialization”.
Note: Through compatibility testing, it has been
observed that some 3rd party Ethernet
products do not transmit link pulses that
are compliant with the IEEE 802.3 stan-
dard timing requirements. For such
devices, the ENCX24J600 PHY energy
detect feature may be unable to wake-up.
Before enabling Energy Detect Power-
Down, application designers should weigh
the compatibility risks of using this feature,
and where possible, implement a means
of disabling it by the end product user.