TLE8386-2EL Datasheet, PDF (27/32 Pages) Infineon Technologies AG – Basic Smart Boost Controller

TLE8386-2EL
Application Information
Input filter capacitor C_IN1 selection:
The input filter capacitor C_IN1 has to compensate the alternate current content or current ripple on the input line,
recommended values are from 10µF to 100µF, to improve the suppression of high frequent distortions a parallel
ceramic capacitor might be necessary.
The RMS input capacitor ripple current I_IN1RMS for a boost converter is:
I_IN1RMS = 0,30 × ∆I_BOOST
Compensation network elements R_COMP, C_COMP selection:
To compensate the feedback loop of the TLE8386-2EL a series network of R_COMP, C_COMP is usually connected from
pin COMP to ground. For most applications the capacitor C_COMP should be in the range of 470pF to 22nF, and the
resistor R_COMP should be in the range of 5kΩ to 100kΩ. An additional capacitor C_COMP2 might be usefull to improve
stability. C_COMP and C_COMP2 should be a low ESR ceramic capacitors.
A practical approach to determine the compensation network is to start with the application circuit as shown in the
data sheet and tune the compensation network to optimize the performance. Stability of the loop should then be
checked under all operating conditions, including output current and variations and over the entire temperature
range.
Output boost voltage V_BO adjustment by determining the output voltage resistor divider R_FBH, R_FBL:
• V_FB = feedback reference voltage
V_BO
=
V_FB
×
R-----_{F---B---H-----}+_{----R-----F--B----L-}
R_FBL
(V_BO is always higher than V_IN during operation of the boost converter)
Additional input filter inductor L_INPUT and capacitor C_IN2 selection:
• f_FILTER = resonance frequency of the additional input filter
The input filter inductor L_INPUT should have a saturation current value equal to L_BOOST, capacitor C_IN2 should be a
low ESR ceramic capacitor. Both elements are forming a low pass filter to suppress conducted disturbances on
the V_IN line. To obtain an optimum suppression, the input filter resonance frequency f_FILTER should be at least ten
times lower than the switching frequency f_FREQ:
f_FREQ
>
10
×



f_FIL
TER
=
-----------------------1-------------------------
2Π L_INPUT × C_IN2
The use of an additional input filter is depending on the requirements of the application.
For selection of R_FREQ, C_SST and C_IVCC please refer to previous chapters.
Data Sheet
25
Rev. 1.0, 2010-10-25