ICS8538BG-31 IDT, Integrated Device Technology Inc, ICS8538BG-31 Datasheet - Page 9

• 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

Power Considerations
This section provides information on power dissipation and junction temperature for the ICS8538-31.
Equations and example calculations are also provided.
1.
The total power dissipation for the ICS8538-31 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
Total Power_
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad and directly affects the reliability of the device.
The maximum recommended junction temperature for HiPerClockS devices is 125°C.
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ
and a multi-layer board, the appropriate value is 49.8°C/W per Table 7 below.
Therefore, Tj for an ambient temperature of 70°C with all outputs switching is:
This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air flow and the type
of board (single layer or multi-layer).
Table 7. Thermal Resistance
NOTE: Most modern PCB design use multi-layered boards. The data in the second row pertains to most designs.
IDT™ / ICS™ LVPECL FANOUT BUFFER
Linear Feet per Minute
Single-Layer PCB, JEDEC Standard Test Boards
Multi-Layer PCB, JEDEC Standard Test Boards
ICS8538-31
LOW SKEW, 1-TO-8, CRYSTAL OSCILLATOR/LVCMOS-TO-3.3V LVPECL FANOUT BUFFER
Power Dissipation.
•
•
Power (core)
Power (outputs)
If all outputs are loaded, the total power is 8 * 30mW = 240mW
The equation for Tj is as follows: Tj = θ
Tj = Junction Temperature
θ
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
T
70°C + 0.621W * 49.8°C/W = 100.9°C. This is well below the limit of 125°C.
JA
A
= Ambient Temperature
= Junction-to-Ambient Thermal Resistance
MAX
(3.3V, with all outputs switching) = 381.15mW + 240mW = 621.15mW
MAX
MAX
= V
= 30mW/Loaded Output pair
CC_MAX
θ
JA
* I
for 28 Lead TSSOP, Forced Convection
EE_MAX
CC
= 3.3V + 5% = 3.465V, which gives worst case results.
JA
= 3.465V * 110mA = 381.15mW
* Pd_total + T
θ
JA
82.9°C/W
49.8°C/W
A
by Velocity
0
9
68.7°C/W
43.9°C/W
200
ICS8538BG-31 REV. B FEBRUARY 5, 2008
JA
must be used. Assuming no air flow
60.5°C/W
41.2°C/W
500