ISL59911_14 Datasheet, PDF (12/17 Pages) Intersil Corporation – 250MHz Triple Differential Receiver/ Equalizer with I2C Interface

ISL59911
Power Dissipation
The ISL59911 is designed to operate with ±5V supply voltages.
The supply currents are tested in production and guaranteed to
be less than 140mA per channel. Operating at ±5V power supply,
the total power dissipation is shown by Equation 1:
PD_MAX
=
2 × V_S × I_SMAX + 3(V_S
-
V_OUTMAX
)
×
V_{----O----U---T---M-----A---X--}
R_L
(EQ. 1)
Where:
• PD_MAX = Maximum power dissipation
• V_S = Supply voltage = 5V
• I_MAX = Maximum quiescent supply current = 140mA
• V_OUTMAX = Maximum output voltage swing of the
application = 2V
• The 3 term comes from the number of channels
• R_L = Load resistance = 150Ω
• PD_MAX = 1.4W
θ_JA required for long term reliable operation can be calculated.
This is done using Equation 2:
θ_JA= (T_J – T_A) ⁄ PD= (46°C) ⁄ W
(EQ. 2)
Where:
T_J is the maximum junction temperature (+150°C)
T_A is the maximum ambient temperature (+85°C)
For a 32 Ld QFN package in a proper layout PCB heatsinking
copper area, 31°C/W θ_JA thermal resistance can be achieved. To
disperse the heat, the bottom heatspreader must be soldered to
the PCB. Heat flows through the heatspreader to the circuit board
copper, then spreads and converts to air. Thus the PCB copper
plane becomes the heatsink. This has proven to be a very
effective technique. A separate application note that details the
32 pin QFN PCB design considerations is available.
12
FN7548.0
September 2, 2011