ICS84330CI Datasheet, PDF (13/20 Pages) Integrated Circuit Systems – 720MHZ, LOW JITTER, CRYSTAL-TO-3.3V DIFFERENTIAL LVPECL FREQUENCY SYNTHESIZER

ICS84330CI Data Sheet
720MHZ, CRYSTAL-TO-LVPECL FREQUENCY SYNTHESIZER
Power Considerations
This section provides information on power dissipation and junction temperature for the ICS84330CI.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the ICS84330CI is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V_CC = 3.3V + 5% = 3.465V, which gives worst case results.
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
• Power (core)_MAX = V_{CC_MAX} * I_{EE_MAX} = 3.465V * 17mA = 58.9mW
• Power (outputs)_MAX = 30mW/Loaded Output Pair
Total Power__MAX (3.465V, with all outputs switching) = 58.9mW + 30mW = 88.9mW
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad 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.
The equation for Tj is as follows: Tj = _JA * Pd_total + T_A
Tj = Junction Temperature
_JA = Junction-to-Ambient Thermal Resistance
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
T_A = Ambient Temperature
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance _JA must be used. Assuming a moderate 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:
85°C + 0.89W * 31.1°C/W = 112.7°C. This is below the limit of 125°C.
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 8A. Thermal Resistance _JA for 28 Lead PLCC, Forced Convection
_JA by Velocity
Linear Feet per Minute
0
Multi-Layer PCB, JEDEC Standard Test Boards
37.8°C/W
200
31.1°C/W
500
28.3°C/W
Table 8B. Thermal Resistance _JA for 32 Lead LQFP, Forced Convection
_JA by Velocity
Linear Feet per Minute
0
200
Single-Layer PCB, JEDEC Standard Test Boards
67.8°C/W
55.9°C/W
Multi-Layer PCB, JEDEC Standard Test Boards
47.9°C/W
42.1°C/W
NOTE: Most modern PCB designs use multi-layered boards. The data in the second row pertains to most designs.
500
50.1°C/W
39.4°C/W
ICS84330CVI REVISION A JANUARY 7, 2011
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©2011 Integrated Device Technology, Inc.