8S89831AKILFT IDT, 8S89831AKILFT Datasheet - Page 15

• Manufacturer Part Number: 8S89831AKILFT
• Description: Clock Drivers & Distribution 1
• Manufacturer: IDT

Specifications of 8S89831AKILFT

• Rohs: yes
• Part # Aliases: ICS8S89831AKILFT

ICS8S89831I Data Sheet
ICS8S89831AKI REVISION A APRIL 26, 2010
Power Considerations
This section provides information on power dissipation and junction temperature for the ICS8S89831I.
Equations and example calculations are also provided.
1.
The total power dissipation for the ICS8S89831I is the sum of the core power plus the power dissipation in the load(s).
The following is the power dissipation for V
NOTE: Please refer to Section 3 for details on calculating power dissipation 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 is 125°C. Limiting the internal transistor junction temperature, Tj, to 125°C ensures that the bond
wire and bond pad temperature remains below 125°C.
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ
a multi-layer board, the appropriate value is 74.7°C/W per Table 6 below.
Therefore, Tj for an ambient temperature of 85°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 (multi-layer).
Table 6. Thermal Resistance
Meters per Second
Multi-Layer PCB, JEDEC Standard Test Boards
Power Dissipation.
•
•
•
Power (core)
Power (outputs)
If all outputs are loaded, the total power is 4 * 32.94mW = 131.76mW
Power Dissipation for internal termination R
Power (R
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
85°C + 0.306W * 74.7°C/W = 107.9°C. This is well below the limit of 125°C.
JA
A
= Ambient Temperature
= Junction-to-Ambient Thermal Resistance
MAX
T
(3.3V, with all outputs switching) = 155.925mW + 131.76mW + 18mW = 305.685mW
)
MAX
MAX
= (V
MAX
= V
IN_MAX
= 32.94mW/Loaded Output pair
CC_MAX
θ
JA
)
2
/ R
* I
for 16 Lead VFQFN, Forced Convection
EE_MAX
T_MIN
CC
= 3.3V + 5% = 3.465V, which gives worst case results.
= (1.2V)
JA
= 3.465V * 45mA = 155.925mW
* Pd_total + T
T
2
/ 80
Ω
= 18mW
θ
JA
A
74.7°C/W
by Velocity
15
0
DIFFERENTIAL LVPECL-TO-LVPECL/ECL FANOUT BUFFER
65.3°C/W
JA
1
must be used. Assuming no air flow and
©2010 Integrated Device Technology, Inc.
58.5°C/W
2.5