ISL24006 Datasheet, PDF (9/10 Pages) Intersil Corporation – 14-Channel Programmable Switchable I2C TFT-LCD Reference Voltage Generator with Integrated 4-Channel Static Gamma Drivers

ISL24006
The maximum power dissipation allowed in a package is
determined according to:
P_DMAX
=
T_{----J---M-----A----X-----}–_-----T_{----A---M-----A----X--}
Θ_JA
where:
• T_JMAX = Maximum junction temperature
• T_AMAX = Maximum ambient temperature
• θ_JA = Thermal resistance of the package
• P_DMAX = Maximum power dissipation in the package
The maximum power dissipation actually produced by the IC
is the total quiescent supply current times the total power
supply voltage and plus the power in the IC due to the loads.
P_DMAX = A_VDD × I_AVDD + Σ[(A _VDD – V_OUTi ) × I_LOADi ]
when sourcing, and:
P_DMAX = A_VDD × I_AVDD + Σ(V_OUTi × I_LOADi)
when sinking.
Where:
• i = 1 to total 14
• A_VDD = Supply voltage
• I_AVDD = Quiescent current
• V_OUTi = Output voltage of the i channel
• I_LOADi = Load current of the i channel
By setting the two P_DMAX equations equal to each other, we
can solve for the R_LOADs to avoid the device overheat. The
package power dissipation curves provide a convenient way
to see if the device will overheat.
Power Supply Bypassing and Printed Circuit
Board Layout
Good printed circuit board layout is necessary for optimum
performance. A low impedance and clean analog ground
plane should be used for the ISL24006. The traces from the
two ground pins to the ground plane must be very short. The
thermal pad should be connected to the analog ground
plane. Lead length should be as short as possible and all
power supply pins must be well bypassed. A 0.1µF ceramic
capacitor must be placed very close to the A_VDD, V_{REFU_H},
V_{REFU_L}, V_{REFL_H}, V_{REFL_L}, and BG pins. A 4.7µF local
bypass ceramic capacitor should be placed to the A_VDD,
V_{REFU_H}, V_{REFU_L}, V_{REFL_H}, V_{REFL_L} pins.
9
FN6110.1
September 9, 2005