ICS843N252-45 Datasheet, PDF (10/16 Pages) Integrated Device Technology – Fourth generation FemtoClock

ICS843N252-45 Data Sheet
FEMTOCLOCK^® CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER
Power Considerations
This section provides information on power dissipation and junction temperature for the ICS843N252-45.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the ICS843N252-45 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V_CC = 3.465V, which gives worst case results.
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
Core and LVPECL Output Power Dissipation
• Power (core)_MAX = V_{CC_MAX} * I_{EE_MAX} = 3.465V * 124mA = 429.66mW
• Power (LVPECL) = 33.75mW/Loaded Output pair
LVCMOS Output Power Dissipation
• Output Impedance R_OUT Power Dissipation due to Loading 50Ω to V_CCOA/2
Output Current I_OUT = V_{CCOA_MAX} / [2 * (50Ω + R_OUT)] = 3.465V / [2 * (50Ω + 15Ω)] = 26.65mA
• Power Dissipation on the R_OUT per LVCMOS output
Power (R_OUT) = R_OUT * (I_OUT)² = 15Ω * (26.65mA)² = 10.65mW per output
• Dynamic Power Dissipation at 125MHz
Power (125MHz) = C_PD * Frequency * (V_CCOA)² = 7pF * 125MHz * (3.465V)² = 10.51mW
Total Power Dissipation
• Total Power
= Power (core) + Power (LVPECL) + Power (R_OUT) + Power (125MHz)
= 429.66mW + 33.75mW + 10.65mW + 10.51mW
= 484.57mW
ICS843N252GG-45 REVISION A JULY 6, 2011
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