EL7156C
High Performance Pin Driver
power dissipation for a given application prior to select-
ing the package type.
where:
• Tjmax is the maximum junction temperature (125°C),
• Tmax is the maximum operating temperature,
• PD is the power dissipation calculated above,
• θja thermal resistance on junction to ambient.
Power dissipation may be calculated:
PD = (VS × IS ) + (CINT × VS2 × f) + (CL × VOUT2 × f)
where:
θja is 160°C/W for the SO8 package and 100°C/W for
the PDIP8 package when using a standard JEDEC
JESD51-3 single-layer test board. If Tjmax is greater than
125°C when calculated using the equation above, then
one of the following actions must be taken:
• VS is the total power supply to the EL7156C (from
VS+ to GND),
• Vout is the swing on the output (VH - VL),
• CL is the load capacitance,
• Reduce θja the system by designing more heat-sinking
into the PCB (as compared to the standard JEDEC
JESD51-3)
• CINT is the internal load capacitance (50pF max.),
• IS is the quiescent supply current (3mA max.) and
• f is frequency
• Use the PDIP8 instead of the SO8 package
Having obtained the application’s power dissipation, a
maximum package thermal coefficient may be deter-
mined, to maintain the internal die temperature below
• De-rate the application either by reducing the switch-
ing frequency, the capacitive load, or the maximum
operating (ambient) temperature (Tmax
)
Tjmax
:
Tjmax – Tmax
θja = --------------------------------
PD
9
ELANTEC [ ELANTEC SEMICONDUCTOR ]
