85354AKLF IDT, Integrated Device Technology Inc, 85354AKLF Datasheet - Page 14

• Manufacturer Part Number: 85354AKLF
• Manufacturer: IDT, Integrated Device Technology Inc

Specifications of 85354AKLF

• Function: Clock Multiplexer
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Package Type: VFQFN
• Pin Count: 16
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

Power Considerations
This section provides information on power dissipation and junction temperature for the ICS85354.
Equations and example calculations are also provided.
1.
The total power dissipation for the ICS85354 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
air flow of 1 meter per second and a multi-layer board, the appropriate value is 65°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 (single layer or multi-layer).
Table 6. Thermal Resitance
IDT™ / ICS™ LVPECL/ECL MULTIPLEXER
Linear Feet per Minute
Multi-Layer PCB, JEDEC Standard Test Boards
ICS85354
DUAL 2:1 AND 1:2, DIFFERENTIAL-TO-LVPECL/ECL MULTIPLEXER
Power Dissipation.
•
•
Power (core)
Power (outputs)
If all outputs are loaded, the total power is 4 * 27.83mW = 111.3mW
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 + 0.285W * 51.5°C/W = 99.7°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) =173.25mW + 111.3mW = 284.55mW
MAX
MAX
= V
= 27.83mW/Loaded Output pair
CC_MAX
θ
JA
for 24 Lead TSSOP, Forced Convection
* I
EE_MAX
CC
= 3.3V + 5% = 3.465V, which gives worst case results.
JA
= 3.465V * 50mA = 173.25mW
* Pd_total + T
θ
JA
51.5°C/W
vs. Air Flow
A
0
14
ICS85354AK REV. C NOVEMBER 04, 2008
JA
must be used. Assuming a moderate