Datasheet

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DP83848T
5.4 Power Feedback Circuit
To ensure correct operation for the DP83848T, parallel
caps with values of 10 µF (Tantalum) and 0.1 µF should
be placed close to pin 19 (PFBOUT) of the device.
Pin 16 (PFBIN1) and pin 30 (PFBIN2) must be connected
to pin 19 (PFBOUT), each pin requires a small capacitor
(0.1 µF). See Figure 13 below for proper connections.
5.5 Power Down
The device can be put in a Power Down mode by setting
bit 11 (Power Down) in the Basic Mode Control Register,
BMCR (0x00h).
5.6 Energy Detect Mode
When Energy Detect is enabled and there is no activity on
the cable, the DP83848T will remain in a low power mode
while monitoring the transmission line. Activity on the line
will cause the DP83848T to go through a normal power up
sequence. Regardless of cable activity, the DP83848T will
occasionally wake up the transmitter to put ED pulses on
the line, but will otherwise draw as little power as possible.
Energy detect functionality is controlled via register
Energy Detect Control (EDCR), address 0x1Dh.
6.0 Reset Operation
The DP83848T includes an internal power-on reset (POR)
function and does not need to be explicitly reset for nor-
mal operation after power up. If required during normal
operation, the device can be reset by a hardware or soft-
ware reset.
6.1 Hardware Reset
A hardware reset is accomplished by applying a low pulse
(TTL level), with a duration of at least 1 µs, to the
RESET_N. This will reset the device such that all registers
will be reinitialized to default values and the hardware
configuration values will be re-latched into the device
(similar to the power-up/reset operation).
6.2 Software Reset
A software reset is accomplished by setting the reset bit
(bit 15) of the Basic Mode Control Register (BMCR). The
period from the point in time when the reset bit is set to the
point in time when software reset has concluded is
approximately 1 µs.
The software reset will reset the device such that all regis-
ters will be reset to default values and the hardware con-
figuration values will be maintained. Software driver code
must wait 3 µs following a software reset before allowing
further serial MII operations with the DP83848T.
0.1µF10 µF
Pin 19 ( PFBOUT )
0.1 µF
0.1 µF
Pin 16 (PFBIN1)
Pin 30 (PFBIN2)
+
-
Figure 13. Power Feeback Connection