TLE42664_15 Datasheet, PDF (11/15 Pages) Infineon Technologies AG – Low Dropout Fixed Voltage Regulator

TLE42664
Application Information
TLE42664 is designed to be stable with extremely low ESR capacitors. According to the automotive environment,
ceramic capacitors with X5R or X7R dielectrics are recommended.
The output capacitor should be placed as close as possible to the regulator’s output and GND pins and on the
same side of the PCB as the regulator itself.
In case of rapid transients of input voltage or load current, the capacitance should be dimensioned in accordance
and verified in the real application that the output stability requirements are fulfilled.
6.3
Thermal Considerations
Knowing the input voltage, the output voltage and the load profile of the application, the total power dissipation
can be calculated:
(1)
P_D = (V_I – V_Q) × I_Q + V_I × I_q
with
• P_D: continuous power dissipation
• V_I: input voltage
• V_Q: output voltage
• I_Q: output current
• I_q: quiescent current
The maximum acceptable thermal resistance R_thJA can then be calculated:
(2)
R_{thJA, max}
=
T----_{j--,--m----a--x----}–_-----T----a
P_D
with
• T_j,max: maximum allowed junction temperature
• T_a: ambient temperature
Based on the above calculation the proper PCB type and the necessary heat sink area can be determined with
reference to the specification in “Thermal Resistance” on Page 6.
Example
Application conditions:
V_I = 13.5 V
V_Q = 5 V
I_Q = 50 mA
T_a = 105 °C
Calculation of R_thJA,max:
P_D = (V_I – V_Q) • I_Q + V_I • I_q
= (13.5 V – 5 V) • 50 mA + 13.5 V • 4 mA
= 0.425 W + 0.054 W
= 0.479 W
Data Sheet
11
Rev. 1.1, 2014-07-03