TLE8386-2EL Datasheet, PDF (25/32 Pages) Infineon Technologies AG – Basic Smart Boost Controller

TLE8386-2EL
Application Information
In fixed frequency mode an external resistor determines the switching frequency. The minimum boost inductor for
fixed frequency is given by the formula below:
• L_BOOSTMIN = minimum Inductance required (minimum value of L_BOOST)
L_BOOST
M
IN
≥
----------V-----^B---^O----^[--V-----^]---^×-----R----^C----^S---^[--^Ω-----^]----------
106×10^–3[V] × f_FREQ[Hz]
Following the previous equations the user should choose the boost inductor having sufficient saturation and RMS
current ratings.
The boost inductor value influences the current ripple ∆I_BOOST:
• A larger boost inductor value decreases the current ripple ∆I_BOOST, but reduces also the current loop gain.
• A lower boost inductor value increases the current ripple ∆I_BOOST, but provides faster transient response. A
lower boost inductor value also results in higher input current ripple and greater core losses.
Output diode D_BOOST selection:
Guidelines to choose the diode:
• Fast switching diode
• Low forward drop
• Low reverse leakage current
• It is recommended to choose the repetitive reverse voltage rating V_RRM (please refer to diode data sheet) at
least 10V higher than the boost converter output voltage V_BO.
The average forward current in normal operation is equal to the boost converter output current I_BO and the peak
current through the diode I_DPEAK (occurs in off-time of the power MOSFET) is:
I_DPEAK = I_BOOSTPEAK = I_BOOSTMAX × _1 + ^χ-2-_
The power dissipation P_LOSSDIO in the output diode D_BOOST is:
P_LOSSDIO = I_BOMAX × V_D
• V_D = forward drop voltage of diode D_BOOST (please refer to diode data sheet).
Data Sheet
23
Rev. 1.0, 2010-10-25