TLE8386-2EL Datasheet, PDF (26/32 Pages) Infineon Technologies AG – Basic Smart Boost Controller

TLE8386-2EL
Application Information
Output filter capacitor C_OUT selection:
Choosing the correct output capacitor for given output ripple voltage, the influence of
• ESR = equivalent series resistance,
• ESL = equivalent series inductance and
• bulk capacitance have to be considered.
The effects of these three parameters is additional ringing on the output voltage V_BO.
The voltage ripple at the output voltage V_BO depends on:
• ∆V_ESR: in percent, related to the ESR of the output capacitor(s)
• ∆V_COUT: in percent, related to the bulk capacitance of the output capacitor(s)
• To receive the total voltage ripple, the influence of ∆V_ESR and ∆V_COUT must be counted together.
The output capacitor can be calculated using the following equation (which contains the influence of the bulk
capacitance on the output voltage ripple):
C_OUT
≥
----------------------I--^B----^O---^M----^A----^X-----------------------
∆V_COUT × V_OUT × f_FREQ
Influence of the capacitor ESR on the output voltage ripple:
ESR_COUT
≤
-^∆----V-----^E---^S--^R--
I_DPEAK
The output capacitor experiences high RMS ripple currents, the RMS ripple current rating can be determined using
the following formula:
I_COUTRMS ≥ I_BOMAX ×
-----D-----^M----^A---^X-------
1 – D_MAX
• I_COUTRMS = RMS ripple current rating at switching frequency I_FREQ.
To meet the ESR requirements often multiple capacitors are paralleled. Typically, once the ESR requirement is
met, the output capacitance is adequate for filtering and has the required RMS current rating. Additional ceramic
capacitors are commonly used to reduce the effects of parasitic inductance to reduce high frequent switching
noise on the boost converter output.
Data Sheet
24
Rev. 1.0, 2010-10-25