MT933 Zarlink Semiconductor, MT933 Datasheet - Page 16

• Manufacturer Part Number: MT933
• Description: MT933 - 3.3V 10/100 Fast Ethernet Transceiver to Mii
• Manufacturer: Zarlink Semiconductor

16
MT933
EXTERNAL COMPONENTS
Connecting an External 25MHz Reference
If an external clock is used then it should be driven
into the REFCLK input, and XTAL1 must be connected
to ground. XTAL2 must be left unconnected. If a
crystal is used, REFCLK must be connected to ground.
RESETN Pull-up Resistor
This resistor is required regardless of whether or not
RESETN is used externally.
RX Input Decoupling
The method of using a split input load resistor and
de-coupling the centre tap reduces common mode
noise.
Vdd
Vdd
Vdd
Vdd
Vdd
10K(5%)
5K(5%)
SUBGND2
RXGND3
RESETN
RXGND2
RXVDD3
RXVDD2
COLST
SPDST
DGND1
LNKST
ACTST
TX_ER
TX_EN
DVDD1
FDST
PA4
30 (1%)
0.01µF
20 (1%) 20 (1%)
Figure 7 External Components
30 (1%)
1:
√
2 MAGNETICS
24.9 (1%)
Crystal Oscillator
For IEEE802.3 compliance the oscillator must run at
25MHz ±100ppm. The MT933 on-chip circuitry
contributes less than 40ppm variability to the oscillator
frequency, therefore the crystal must be specified to
60ppm. This must include variations due to
temperature and ageing. The crystal must be capable
of dissipating 0.5mW of power.
External capacitors are required on the XTAL1 &
XTAL2 pins. Manufacturer's recommendations should
be followed.
Tracking to the crystal and the capacitors must be as
short as possible. Other signal paths must not cross
the area.
The MT933 is supported by the following magnetics:
VENDOR
24.9 (1%)
Pulse
0.01µF
10
DVDD3
MDIO
TXVDD4
TXREF10
TXVDD3
TXGND3
MINT
MDC
DGND3
RefCLK
OSCVDD
XTAL1
XTAL2
OSCGND
TXCGND4
TXREF100
1.24K
1%
MAGNETICS
H1119
25MHz
C2
1.24K
1%
C2
Vdd