MIC24046 Datasheet, PDF (22/27 Pages) Micrel Semiconductor – Pin-Programmable, 4.5V − 19V, 5A Step-Down Converter

Micrel, Inc.
frequency. For example, setting the compensator pole at
5 f_XO, will limit its associated phase loss at the crossover
frequency to about 11°. Placement at even higher
frequencies N × f_XO (N > 5) will reduce phase loss even
further, at the expense of less noise/ripple attenuation at
the switching frequency. Some attenuation of the
switching frequency noise/ripple is achieved as long as N
× f_XO < f_S.
For polarized output capacitor, compensator pole
placement at the ESR zero frequency is achieved shown
in Equation 23:
C_C2 =
1
R_{C1 −} 1
C_O × ESR C_C1
Eq. 23
For ceramic output capacitor, compensator pole
placement at N × f_XO (N ≥ 5, N × f_XO < f_S) is achieved as
detailed in Equation 24:
C_C2
=
2π × R_C1
1
× N × f_XO
−
1
C_C1
Eq. 24
Output Voltage Soft-Start Rate
The MIC24046 features internal analog soft-start, such
that the output voltage can be smoothly increased to the
target regulation voltage. The soft-start rate given in the
Electrical Characteristics is referred to the error amplifier
reference, and therefore the effective soft-start rate value
seen at the output of the module has to be scaled
according to the internal feedback divider attenuation
values listed in Table 5. To calculate the effective output
voltage soft-start slew rate SS_SR_OUT based on the
particular output voltage setting and the reference soft-
start slew rate SS_SR, use the following formula:
SS _ SR_OUT = A ⋅ SS _ SR
Eq. 25
Where:
The value of A (amplification, A =1 + R2/R1) is given in
the right column of Table 5.
October 14, 2015
22
MIC24046
Revision 1.1