ICS8538BG-31 IDT, Integrated Device Technology Inc, ICS8538BG-31 Datasheet - Page 8

• Manufacturer Part Number: ICS8538BG-31
• Manufacturer: IDT, Integrated Device Technology Inc
• Type: Clock Driverr

Specifications of ICS8538BG-31

• Number Of Clock Inputs: 2
• Mode Of Operation: Single-Ended
• Output Frequency: 266MHz
• Output Logic Level: LVPECL
• Operating Supply Voltage (min): 3.135V
• Operating Supply Voltage (typ): 3.3V
• Operating Supply Voltage (max): 3.465V
• Package Type: TSSOP
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Signal Type: LVCMOS/LVTTL
• Mounting: Surface Mount
• Pin Count: 28
• Lead Free Status / RoHS Status: Not Compliant

Recommendations for Unused Input and Output Pins
Inputs:
Crystal Inputs
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.
CLK Input
For applications not requiring the use of a clock input, it can be left
floating. Though not required, but for additional protection, a 1kΩ
resistor can be tied from the CLK input 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.
Termination for 3.3V LVPECL Outputs
The clock layout topology shown below is a typical termination for
LVPECL outputs. The two different layouts mentioned are
recommended only as guidelines.
FOUT and nFOUT are low impedance follower outputs that
generate ECL/LVPECL compatible outputs. Therefore, terminating
resistors (DC current path to ground) or current sources must be
used for functionality. These outputs are designed to drive 50Ω
Figure 4A. 3.3V LVPECL Output Termination
IDT™ / ICS™ LVPECL FANOUT BUFFER
ICS8538-31
LOW SKEW, 1-TO-8, CRYSTAL OSCILLATOR/LVCMOS-TO-3.3V LVPECL FANOUT BUFFER
RTT =
((V
FOUT
OH
+ V
OL
) / (V
1
CC
Z
Z
– 2)) – 2
o
o
= 50
= 50
Z
o
50
RTT
50
V
CC
FIN
- 2V
8
Outputs:
LVPECL Outputs
All unused LVPECL outputs can be left floating. We recommend
that there is no trace attached. Both sides of the differential output
pair should either be left floating or terminated.
transmission lines. Matched impedance techniques should be
used to maximize operating frequency and minimize signal
distortion. Figures 4A and 4B show two different layouts which are
recommended only as guidelines. Other suitable clock layouts may
exist and it would be recommended that the board designers
simulate to guarantee compatibility across all printed circuit and
clock component process variations.
Figure 4B. 3.3V LVPECL Output Termination
FOUT
Z
Z
o
o
= 50
= 50
ICS8538BG-31 REV. B FEBRUARY 5, 2008
125
84
3.3V
125
84
FIN