DS1080CL Datasheet, PDF (7/8 Pages) Maxim Integrated Products – Spread-Spectrum Crystal Multiplier

Spread-Spectrum Crystal Multiplier
Applications Information
Crystal Selection
The DS1080CL requires a parallel resonating crystal
operating in the fundamental mode, with an ESR of less
than 90Ω. The crystal should be placed very close to
the device to minimize excessive loading due to para-
sitic capacitances.
Oscillator Input
When driving the DS1080CL using an external oscillator
clock, consider the input (X1) to be high impedance.
Crystal Capacitor Selection
The load capacitors C_L1 and C_L2 are selected based
on the crystal specifications (from the data sheet of the
crystal used). The crystal parallel load capacitance is
calculated as follows:
C_L
=
C_L1 x
C_L1 +
C_L2
C_L2
+ C_IN
(1)
For the DS1080CL use C_L1 = C_L2 = C_LX.
In this case, the equation then reduces to:
C_L
=
C_LX
2
+ C_IN
(2)
where C_L1 = C_L2 = C_LX.
Equation 2 is used to calculate the values of C_L1 and
C_L2 based on values of C_L and C_IN noted in the electri-
cal specifications.
Power-Supply Decoupling
To achieve best results, it is highly recommended that
a decoupling capacitor is used on the IC power-supply
pins. Typical values of decoupling capacitors are
0.001μF and 0.1μF. Use a high-quality, ceramic, sur-
face-mount capacitor, and mount it as close as possi-
ble to the V_CC and GND pins of the IC to minimize lead
inductance.
Layout Considerations
As noted earlier, the crystal should be placed very
close to the device to minimize excessive loading due
to parasitic capacitances. Care should also be taken to
minimize loading on pins that could be open as a pro-
gramming option (SMSEL and CMSEL). Coupling on
inputs due to clocks should be minimized.
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
8 μSOP
PACKAGE
CODE
U8+1
OUTLINE
LAND
NO. PATTERN NO.
21-0036
90-0092
_______________________________________________________________________________________ 7