AMD
TAXI Technical Information Publication #89-05
S u b je c t : TAXIc h ip S e t Crys t a l S p e c ific a t io n
Qu e s t io n :
What are the design considerations for crystals used with TAXIchip set?
An s w e r:
The TAXIchip’s parallel mode oscillator uses a 4.0 MHz – 17.5 MHz crystal with a
frequency tolerance of 0.1%.
Any crystal will oscillate in either series or parallel mode depending upon the type of
oscillator used. By specifying parallel mode and the load, the manufacturer will calibrate
the crystal in parallel mode at the desired frequency. This could be important in
applications where frequency tolerance is critical due to the fact that the resonant
frequency in parallel mode is typically 0.02% above the series mode frequency.
As discussed in section 3.3, the time required to synchronize the data recovery circuit in
the Receiver is proportional to the delta between the Transmitter frequency and the
Receiver PLL resting frequency. The Receiver resting frequency is typically less than
±1% away from its own crystal frequency, due to mismatch between internal circuits.
The crystal specification of 0.1% is meant to be small enough to cause a negligible
effect on lock time while not increasing the crystal cost (0.025% crystals are quite
common). Sometimes tighter frequency and tolerance specifications may be necessary
to meet the user’s system requirements (i.e. FIFO depth, etc.).
More information on crystal specifications for the TAXIchip set may be found in
Section 4.1.1.
A partial list of vendors follows:
Typical 12.5 MHz
Distributor
Part Number
Phone Number
I.E.A.
HC18U 12.500
UM-12.5
(408) 435-1000
(714) 957-1299
(619) 433-4510
(814) 695-4428
(408) 733-0384
Calmax Corp.
Monitor Products
MM 49XlE12A-12.5
Anderson Electronics 011-668-03260
Target Electronics CC025A-12.5
TAXIchip Integrated Circuits Technical Manual
99
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