MAX15041 Maxim Integrated Products, MAX15041 Datasheet - Page 14

• Manufacturer Part Number: MAX15041
• Description: Step-Down DC-DC Regulator
• Manufacturer: Maxim Integrated Products

Low-Cost, 3A, 4.5V to 28V Input, 350kHz, PWM
Step-Down DC-DC Regulator with Internal Switches
For R
further simplified as follows:
where V
3) Select C
therefore:
4) If the ESR output zero is located at less than one-half
therefore:
If the ESR zero exceeds 1/2 the switching frequency,
use the following equation:
therefore:
The downside of C
system phase margin. Care should be taken to guarantee
14
desired first system zero, f
phase margin. Typically, setting f
f
the switching frequency use the (optional) sec-
ondary compensation capacitor, C
as follows:
CO
______________________________________________________________________________________
LOAD
provides sufficient phase margin.
2
FB
π
×
is equal to 0.606V.
much greater than ESR, the equation can be
C
R
C
1
C
CC C
. C
f
P
f
=
Z
R
3
C
C
1
C
C
V
CC
CC
=
CC
V
=
OUT
C
FB
is determined by selecting the
=
2
2
≥
π
=
π
=
f
is that it detracts from the overall
P
2π
×
3
×
2π
×
C
C
C R
OUT
1
=
2π
1
×
CC C
×
C C
f
g
Z
f
CO
f
×
MV
SW
R
2
5
Z1
R
2
f
C
×
CO
=
, based on the desired
×
×
≤
×
2
ESR
=
R
G
f
R
π
×
CO
C
MOD
f
5
C
SW
×
C
2
Z1
OUT
C
CC
OUT
1
below 1/5th of
, to cancel it,
ESR
this third-pole placement is well beyond the desired
crossover frequency, minimizing its interaction with the
system loop response at crossover. If C
10pF, it can be neglected in these calculations.
The soft-start feature ramps up the output voltage slow-
ly, reducing input inrush current during startup. Size the
C
using:
I
put feedback voltage threshold, is 0.606V (typ). When
using large C
current limit may trigger during the soft-start period. To
ensure the correct soft-start time, t
enough to satisfy:
I
limit value.
The MAX15041 is available in a thermally enhanced
TQFN package and can dissipate up to 1.666W at T
+70°C. The exposed pad should be connected to
SGND externally, preferably soldered to a large ground
plane to maximize thermal performance. When the die
temperature exceeds +155°C, The thermal-shutdown
protection is activated (see the Thermal-Shutdown
Protection section).
Careful PCB layout is critical to achieve clean and sta-
ble operation. It is highly recommended to duplicate
the MAX15041 evaluation kit layout for optimum perfor-
mance. If deviation is necessary, follow these guide-
lines for good PCB layout:
1) Connect input and output capacitors to the power
SS
HSCL_MIN
SS
ground plane; connect all other capacitors to the
signal ground plane.
, the soft-start current, is 5µA (typ) and V
capacitor to achieve the desired soft-start time t
C
SS
is the minimum high-side switch, current-
>>
OUT
C
OUT
capacitance values, the high-side
C
Setting the Soft-Start Time
SS
×
(
I
HSCL MIN
=
I
SS
V
_
×
FB
V
t
OUT
Power Dissipation
SS
Layout Procedure
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SS
−
×
, choose C
I
OUT
I
CC
SS
is smaller than
)
×
FB
V
FB
, the out-
SS
large
A
SS
=