AC1040F Datasheet, PDF (14/37 Pages) List of Unclassifed Manufacturers – Ultra Low Power 10/100 Quad RMII Ethernet Transceiver

AC104QF
Ultra Low Power 10/100 Quad RMII Ethernet Transceiver
pattern is repeated 3 times. A FEFI will signal under
3 conditions: 1) When no activity is received from
the link partner, 2) When the clock recovery circuit
detects a signal error or PLL lock error, 3) When
management entity sets the transmit Far-End-Fault
bit.
The FEFI mechanism is enabled by default in the
100Base-FX mode, and is disabled in 100Base-TX or
10Base-T modes. The register setting can be changed
by software after reset.
10BASE-T/100BASE-TF/FX
meter cable is 21 dB. The worst case cable
attenuation is around 24-26 dB as defined by TP-
PMD specification.
The amplitude and phase distortion from the cable
cause inter-symbol interference (ISI) which makes
clock and data recovery difficult. The adaptive
equalizer si designed to closely match the inverse
transfer function of the twisted-pair cable. The
equalizer has the ability to changes its equalizer
frequency response according to the cable length.
The equalizer will tune itself automatically for any
cable, compensating for the amplitude and phase
distortion introduced by the cable.
Multi-Mode Transmit Driver
The multi-mode driver transmits the MLT-3 coded
signal in 100Base-TX mode, NRZI coded signal in
100Base-FX mode, and Manchester coded signal in
10Base-T mode.
In 100Base-FX mode, no filtering is performed. The
transmit driver utilizes a current drive output which is
well balanced and produces a low noise PECL signal.
PECL voltage levels are produced with resistive
terminations.
In 10BaseT mode, high frequency pre-emphasis is
performed to extend the cable-driving distance
without the external filter. The FLP and NLP pulses
are also drive out through the 10BaseT driver.
The 10BaseT and 100BaseTX transmit signals are
multiplexed to the transmit output driver. This
arrangement results in using the same external
transformer for both the 10BaseT and the
100BaseTX. The driver output level is set by a built-
in bandgap reference and an external resistor
connected to the IBREF pin. The resistor sets the
output current for all modes of operation. The
TXOP/N outputs are open drain devices with a serial
source to I/O pad resistance of 10 Ω max. When the
1:1 transformer is used, the current rating is 40 mA
for the 2Vp-p MLT-3 signal, and 100 mA for the
5Vp-p Manchester signal. One can use a 1.25:1
transmit transformer for a 20% output driver power
reduction. This will decrease the drive current to 32
mA for 100Base-TX operation, and 80 mA for
10Base-T operation.
PLL Clock Synthesizer
The Phy includes an on-chip PLL clock synthesizer
that generate 25 MHz and 125 MHz clocks for the
100Base-TX circuitry. It also generates 20 MHz and
100 MHz clocks for the 10BaseT and ANeg circuitry.
The PLL clock generator uses a fully differential
VCO cell that introduces very low jitter. The Zero
Dead Zone Phase Detection method implemented in
the Phy design provides excellent phase tracking. A
charge pump with charge sharing compensation is
also included to further reduce jitter at different loop
filter voltages. The on-chip loop filter eliminates the
need for external components and minimizes the
external noise sensitivity. Only one external 50 MHz
(RMII) or 25 MHz (MII) crystal or clock source is
required as a reference clock.
After power-on or reset, the PLL clock synthesizer
generates the 20 MHz clock output until the
100Base-X operation mode is selected.
Jabber and SQE (Heartbeat)
After the MAC transmitter exceeds the jabber timer
(46mS), the transmit and loopback functions will be
disabled and COL signal get asserted. After TX_EN
goes low for more than 500 ms, the TP transmitter
will reactivate and COL gets de-asserted. Setting
Jabber Disable will disable the jabber function.
When the SQE test is enabled, a COL pulse with 5-
15BT is asserted after each transmitted packet. SQE
is enabled in 10Base-T by default, and can be
disabled via SQE Test Inhibit.
Adaptive Equalizer
The Phy is designed to accommodate a maximum of
150 meters UTP CAT-5 cable. An AT&T 1061 CAT-
5 cable of this length typically has an attenuation of
31 dB at 100 MHz. A typical attenuation of 100-
Reverse Polarity Detection and Correction
Certain cable plants have crossed wiring on the
twisted pairs; the reversal of TXIN and TXIP. Under
normal circumstances this would cause the receive
circuitry to reject all data. When the Auto Polarity
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