MAX15066EWE+T Maxim Integrated Products, MAX15066EWE+T Datasheet - Page 18

• Manufacturer Part Number: MAX15066EWE+T
• Description: DC/DC Switching Controllers 4A 12V 500kHz w/Integrated Switch
• Manufacturer: Maxim Integrated Products

Specifications of MAX15066EWE+T

• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

High-Efficiency, 4A, Step-Down DC-DC
Regulator with Internal Power Switches
1) Select the desired crossover frequency. Choose f
2) Select R
and where the ESR is much smaller than the parallel
combination of the equivalent load resistance and the
current-loop impedance, e.g.,:
R
3) Select C
therefore:
18
R
C
C
between 1/5 to 1/10 of f
asymptote gain equal to unity (assuming f
f
first system zero, f
margin. Typically, setting f
vides sufficient phase margin.
becomes:
P2
=
_____________________________________________________________________________________
, and f
R1 R2
R2
+
ESR








C
ESR
C
P1
×
. C
R




). R
<<
C
1
by setting the system transfer’s fourth
C
+
+
f
=
Z1
g
R




is determined by selecting the desired




C
C
R
MV
R1 R2
R
LOAD S
=
C
LOAD
becomes:
LOAD
R2
1
+
Closing the Loop: Designing the
2
×
1
≥
Z1
π ×
g
K
2
L f
MC
, based on the desired phase
π ×
+
×
×
C R
SW
+
1


K
(
2 f
1 D
×
C C
SW
K
f
S
CO
−
π
R
1
g
.
5


S
Z1
Compensation Circuitry
LOAD
(
MV
L f
1
CO
1 D


)
(
−
×
×
L f
1 D
−
≤
below 1/5 of f
R
−
×
×
0.5
SW
×
)
f
C
CO
g
C
−
SW
5


)
MC
0.5
OUT




−
× π
0.5


2 f














CO OUT




CO
C
CO
> f
pro-
×
CO
Z1
,
Optional: For low duty-cycle applications, the addition
of a phase-leading capacitor (C
mitigate the phase lag of the damped half-frequency
double pole. Adding a second zero near to but below
the desired crossover frequency increases both the
closed-loop phase margin and the regulator’s unity-gain
bandwidth (crossover frequency). Select the capacitor
as follows:
This guarantees the additional phase-leading zero
occurs at a frequency lower than f
Using C
Confirm the desired operation of C
phase lead of C
smaller multiple of the reference voltage, e.g., below
about 1V. Do not use C
The soft-start feature ramps up the output voltage slowly,
reducing input inrush current during startup. Size the
C
using:
I
feedback voltage threshold, is 0.606V (typ). When using
large C
limit can trigger during soft-start period. To ensure the
correct soft-start time t
satisfy:
I
SS
HSCL
SS
, the soft-start current, is 5FA (typ) and V
capacitor to achieve the desired soft-start time (t
is the typical high-side switch current-limit value.
f
OUT
FF
P1
C
, the zero-pole order is adjusted as follows:
<
SS
f
capacitance values, the high-side current
P2
f
PHASE_LEAD
>>
C
≤
FF
FF
C
f
Z1
diminishes as the output voltage is a
OUT
≈
=
C
<
Setting the Soft-Start Time
f
SS
2
CO
2 C R1 2 C
SS
π ×
FF
×
π
=
, choose C
(I
<
when V
f
1
I
HSCL
FF
CO
=
SS
f
P3
2
V
1
π ×
×
V
FB
×
<
OUT
<
t
(
−
R1|| R2
f
SS
OUT
FF
C
Z2
CO
I
1
OUT
π
FF
FF
×
SS
in Figure 3) helps
from:
I
FF
×
= V
SS
)
) V
R1
empirically. The
large enough to
1
(R1|| R2)
×
FB
FB
FB
.
, the output
SS
)