ics84330c Integrated Device Technology, ics84330c Datasheet - Page 13

• Manufacturer Part Number: ics84330c
• Description: 700mhz, Low Jitter, Crystal-to-3.3v Differential Lvpecl Frequency Synthesizer
• Manufacturer: Integrated Device Technology

Power Considerations
This section provides information on power dissipation and junction temperature for the ICS84330C.
Equations and example calculations are also provided.
1.
The total power dissipation for the ICS84330C 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.
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 200 linear feet per minute and a multi-layer board, the appropriate value is 31.1°C/W per Table 8A 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 8A. Thermal Resistance
Table 8B. Thermal Resistance
IDT™ / ICS™ LVPECL FREQUENCY SYNTHESIZER
Linear Feet per Minute
Multi-Layer PCB, JEDEC Standard Test Boards
Linear Feet per Minute
Single-Layer PCB, JEDEC Standard Test Boards
Multi-Layer PCB, JEDEC Standard Test Boards
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
ICS84330C
700MHZ, LOW JITTER, CRYSTAL-TO-3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER
Power Dissipation.
•
•
Power (core)
Power (outputs)
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 + 0.640W * 31.1°C/W = 89.9°C. This is well below the limit of 125°C.
Total Power_
JA
A
= Ambient Temperature
= Junction-to-Ambient Thermal Resistance
MAX
MAX
MAX
= V
(3.465V, with all outputs switching) = 609.8mW + 30mW = 639.8mW
=30mW/Loaded Output Pair
CC_MAX
θ
θ
JA
JA
* I
EE_MAX
for 28 Lead PLCC, Forced Convection
for 32 Lead LQFP, Forced Convection
CC
= 3.3V + 5% = 3.465V, which gives worst case results.
JA
= 3.465V * 176mA = 609.8mW
* Pd_total + T
θ
θ
JA
37.8°C/W
JA
67.8°C/W
47.9°C/W
A
by Velocity
by Velocity
0
0
14
55.9°C/W
31.1°C/W
42.1°C/W
200
200
JA
ICS84330CV REV. C JANUARY 28, 2009
must be used. Assuming a moderate
28.3°C/W
50.1°C/W
39.4°C/W
500
500