SI53305 Datasheet, PDF (12/36 Pages) Silicon Laboratories – 1:10 LOW JITTER UNIVERSAL BUFFER/LEVEL TRANSLATOR WITH 2:1 INPUT MUX AND INDIVIDUAL OE

Si53305
2. Functional Description
The Si53305 is a low jitter, low skew 1:10 differential buffer with an integrated 2:1 input mux and individual OE
control. The device has a universal input that accepts most common differential or LVCMOS input signals. A clock
select pin is used to select the active input clock. The Si53305 features two control pins to select the signal format
and LVCMOS drive strength settings. In addition, each clock output has an independent OE pin for individual clock
enable/disable.
2.1. Universal, Any-Format Input
The universal input stage enables simple interfacing to a wide variety of clock formats, including LVPECL, low-
power LVPECL, LVCMOS, LVDS, HCSL, and CML. Tables 15 and 16 summarize the various ac- and dc-coupling
options supported by the device. For the best high-speed performance, the use of differential formats is
recommended. For both single-ended and differential input clocks, the fastest possible slew rate is recommended
as low slew rates can increased the noise floor and degrade jitter performance. Though not required, a minimum
slew rate of 0.75 V/ns is recommended for differential formats and 1.0 V/ns for single-ended formats. See “AN766:
Understanding and Optimizing Clock Buffer’s Additive Jitter Performance” for more information.
Table 15. LVPECL, LVCMOS, and LVDS Input Clock Options
1.8 V
2.5/3.3 V
LVPECL
AC-Couple DC-Couple
N/A
N/A
Yes
Yes
LVCMOS
AC-Couple DC-Couple
No
No
No
Yes
LVDS
AC-Couple DC-Couple
Yes
No
Yes
Yes
Table 16. HCSL and CML Input Clock Options
1.8 V
2.5/3.3 V
HCSL
AC-Couple DC-Couple
No
No
Yes (3.3 V) Yes (3.3 V)
CML
AC-Couple DC-Couple
Yes
No
Yes
No
0.1 µF
CLKx
Si53305
100 
CLKx
0.1 µF
Figure 2. Differential HCSL, LVPECL, Low-Power LVPECL, LVDS, CML AC-Coupled Input
Termination
V_DD
VDDO_{= 3.3 V or 2.5 V}
CMOS
Driver
Rs
1 k
V_DD
Si53305
CLKx
50
CLKx
V_TERM = V_DD/2
1 k
VREF
Figure 3. LVCMOS DC-Coupled Input Termination
12
Rev. 1.0