IR3829MTRPBF Datasheet, PDF (30/50 Pages) Infineon Technologies AG – 16A Highly Integrated Single-Input Synchronous SupIRBuck® Regulator

IR3829
Applications Design Example
the Equivalent Series Inductance (ESL) are other contributing components. These components can be described
as:
 V_o  V_o(ESR)  V_o(ESL)  V_{o(C )}
V_{o( ESR)}  I_L  ESR
V_{o ( ESL)}

(^Vin
 V_o
L
)  ESL
V_{o (C )}

I _L
8 C_o  F_s
Where:
ΔV_O = Output Voltage Ripple
ΔI_L = Inductor Ripple Current
Since the output capacitor has a major role in the overall performance of the converter and determines the result
of transient response, selection of the capacitor is critical. The IR3829 can perform well with all types of capacitors.
As a rule, the capacitor must have low enough ESR to meet output ripple and load transient requirements.
The goal for this design is to meet the voltage ripple requirement in the smallest possible capacitor size. Therefore
it is advisable to select ceramic capacitors due to their low ESR and ESL and small size. In this case a good choice
is six 47uF ceramic capacitors, C2012X5R0J476M from TDK. The ESR of this type of capacitor is around 3mΩ
each. The de-rated capacitance value with 1.0VDC bias and 10mVAC voltage is around 29uF each.
It is also recommended to use a 0.1µF ceramic capacitor at the output for high frequency filtering.
7.8
Feedback Compensation
For this design, the resonant frequency of the output LC filter, F_LC, is:
F_LC  _{2  }
1
L_o  C_o
1

2   0.4 10^6  6  29 10^6
 19.1kHz
The equivalent ESR zero of the output capacitors, F_ESR, is:
F_ESR

2
1
 ESR C_o
1
 _{2  3103  29 106}
 1.8MHz
Designing crossover frequency around 1/7th of switching frequency gives F_O =80 kHz.
According to Table 6-1, Type III B compensation is selected for F_LC < F_O <F_S/2 < F_ESR. Type III compensator is
shown in Figure 7-4 for easy reference.
Datasheet
30
Rev 3.7 03/24/2016