ISL59311_14 Datasheet, PDF (13/14 Pages) Intersil Corporation – Differential Video Amplifier with Common Mode Sync Encoder and Serial Digital Interface

ISL59311
Power Dissipation Calculation
When switching at high speeds, or driving heavy loads, the
ISL59311 drive capability is ultimately limited by the rise in die
temperature brought about by internal power dissipation. For
reliable operation die temperature must be kept below T_JMAX
(+125°C). It is necessary to calculate the power dissipation for
a given application prior to selecting package type. Power
dissipation may be calculated:
4
PD = (V_S × I_S) × Σ(C_INT × V_S2 × f) + (C_L × V_{O2 UT} × f)
1
where:
• V_S is the total power supply to the ISL59311 (= V_CCD)
• V_OUT is the swing on the output (V_H - V_L)
• C_L is the load capacitance
• C_INT is the internal load capacitance (80pF max)
• I_S is the quiescent supply current
• f is frequency
Having obtained the application's power dissipation, the
maximum junction temperature can be calculated:
T_JMAX = T_MAX + Θ_JA × PD
where:
• T_JMAX is the maximum junction temperature (+125°C)
• T_MAX is the maximum ambient operating temperature
• PD is the power dissipation calculated above
θ_JA is the thermal resistance, junction to ambient, of the
application (package + PCB combination). Refer to the
Package Power Dissipation curves. See Technical Bulletin
389 (http://www.intersil.com/data/tb/TB389.pdf) for additional
QFN PCB layout information.
13
FN6372.3
April 25, 2007