ICS844002I-01 Datasheet, PDF (8/12 Pages) Integrated Circuit Systems – FEMTOCLOCKS™ CRYSTAL-TO-LVDS FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS844002I-01
FEMTOCLOCKS™ CRYSTAL-TO-
LVDS FREQUENCY SYNTHESIZER
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
INPUTS:
CRYSTAL INPUT:
For applications not requiring the use of the crystal oscillator
input, both XTAL_IN and XTAL_OUT can be left floating.
Though not required, but for additional protection, a 1kΩ
resistor can be tied from XTAL_IN to ground.
OUTPUTS
LVDS
All unused LVDS output pairs can be either left floating or
terminated with 100Ω across. If they are left floating, we
recommend that there is no trace attached.
REF_CLK INPUT:
For applications not requiring the use of the reference clock,
it can be left floating. Though not required, but for additional
protection, a 1kΩ resistor can be tied from the REF_CLK to
ground.
LVCMOS CONTROL PINS:
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1kΩ resistor can be used.
2.5V LVDS DRIVER TERMINATION
Figure 3 shows a typical termination for LVDS driver in
characteristic impedance of 100Ω differential (50Ω single)
transmission line environment. For buffer with multiple LDVS
driver, it is recommended to terminate the unused outputs.
2.5V
LVDS_Driv er
R1
100
100 O₁h₀m_0ΩD_Dif_if_fe_fer_re_en_nt_ti_ia_al_l T_Trra_ann_ss_mm_isis_ss_ioio_nn_LL_inin_ee
2.5V
+
-
FIGURE 3. TYPICAL LVDS DRIVER TERMINATION
844002AGI-01
www.icst.com/products/hiperclocks.html
8
REV. A JANUARY 5, 2006