TJ4230 Datasheet, PDF (8/9 Pages) HTC Korea TAEJIN Technology Co. – 3A Ultra Low Dropout Linear Regulator

3A Ultra Low Dropout Linear Regulator
TJ4230
where T_J is the junction temperature, T_C is the case temperature, T_A is the ambient temperature, P_D is the
total power dissipation of the device, θ_CA is the thermal resistance of case-to-ambient, θ_JC is the thermal
resistance of junction-to-case, and θ_JA is the thermal resistance of junction to ambient.
The total power dissipation of the device is given by:
P_D = P_IN – P_OUT = (V_IN X I_IN)–(V_OUT X I_OUT)
= (V_IN X (I_OUT+I_GND)) – (V_OUT X I_OUT) = (V_IN - V_OUT) X I_OUT + V_IN X I_GND
where I_GND is the operating ground current of the device which is specified at the Electrical Characteristics.
The maximum allowable temperature rise (T_Rmax) depends on the maximum ambient temperature (T_Amax)
of the application, and the maximum allowable junction temperature (T_Jmax):
T_Rmax = T_Jmax – T_Amax
The maximum allowable value for junction-to-ambient thermal resistance, θ_JA, can be calculated using the
formula:
θ_JA = T_Rmax / P_D
TJ4230 is available in SOP8-PP, TO252 and TO263 packages. The thermal resistance depends on
amount of copper area or heat sink, and on air flow.
If proper cooling solution such as heat sink, copper plane area, or air flow is applied, the maximum
allowable power dissipation could be increased. However, if the ambient temperature is increased, the
allowable power dissipation would be decreased.
The graph above is valid for the thermal impedance specified in the Absolute Maximum Ratings section
on page 1.
Apr. 2011 – Rev. 1. 0
8/9
HTC