MP1423DN データシートの表示（PDF） - Monolithic Power Systems
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MP1423DN Datasheet PDF : 11 Pages
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TM
MP1423 – 3A, 23V, 385KHz STEP-DOWN CONVERTER
To optimize the compensation components for
conditions not listed in Table 2, the following
procedure can be used.
1. Choose the compensation resistor (R3) to set
the desired crossover frequency. Determine the
R3 value by the following equation:
R3 = 2π × C2 × fC × VOUT
GEA × GCS VFB
Where fC is the desired crossover frequency
(which typically has a value no higher than
38KHz).
2. Choose the compensation capacitor (C3) to
achieve the desired phase margin. For
applications with typical inductor values, setting
the compensation zero, fZ1, below one forth of
the crossover frequency provides sufficient
phase margin. Determine the C3 value by the
following equation:
C3 >
4
2π × R3 × fC
Where R3 is the compensation resistor value.
3. Determine if the second compensation
capacitor (C6) is required. It is required if the
ESR zero of the output capacitor is located at
less than half of the 385KHz switching
frequency, or the following relationship is valid:
1
< fS
2π × C2 × RESR 2
If this is the case, then add the second
compensation capacitor (C6) to set the pole fP3
at the location of the ESR zero. Determine the
C6 value by the equation:
C6 = C2 × RESR
R3
External Bootstrap Diode
It is recommended that an external bootstrap
diode be added when the system has a 5V
fixed input or the power supply generates a 5V
output. This helps improve the efficiency of the
regulator. The bootstrap diode can be a low
cost one such as IN4148 or BAT54.
1
BS
5V
BOOST
DIODE
MP1423
SW 3
10nF
MP1423_F02
Figure 2—External Bootstrap Diode
This diode is also recommended for high duty
cycle operation (when VOUT >65%) and high
VIN
output voltage (VOUT>12V) applications.
MP1423 Rev. 1.1
www.MonolithicPower.com
8
1/6/2006
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© 2006 MPS. All Rights Reserved.
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