MAX15112EVKIT# Maxim Integrated, MAX15112EVKIT# Datasheet - Page 15

• Manufacturer Part Number: MAX15112EVKIT#
• Description: Power Management IC Development Tools MAX15112 Eval Kit
• Manufacturer: Maxim Integrated
• Type: Power Switchesr
• Series: MAX15112r

Specifications of MAX15112EVKIT#

• Rohs: yes
• Product: Evaluation Kits
• Tool Is For Evaluation Of: MAX15112
• Input Voltage: 2.7 V to 5.5 V
• Output Voltage: 0.6 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Output Current: 12 A
• For Use With: MAX15112

The key selection parameters for the output capacitor are
capacitance, ESR, ESL, and voltage-rating requirements.
These affect the overall stability, output-ripple voltage,
and transient response of the DC-DC converter. The out-
put ripple occurs due to variations in the charge stored in
the output capacitor, the voltage drop due to the capaci-
tor’s ESR, and the voltage drop due to the capacitor’s
ESL. Estimate the output-voltage ripple due to the output
capacitance, ESR, and ESL as follows:
where the output ripple due to output capacitance, ESR,
and ESL is:
and V
divider from LX to GND:
where V
The peak-to-peak inductor current (DI
When using ceramic capacitors, which generally have
low-ESR, DV
lytic capacitors, DV
capacitors for low ESR and low ESL at the switching fre-
quency of the converter. The ripple voltage due to ESL is
negligible when using ceramic capacitors.
As a general rule, a smaller inductor-ripple current results
in less output-ripple voltage. Since inductor-ripple cur-
rent depends on the inductor value and input voltage, the
output-ripple voltage decreases with larger inductance
and increases with higher input voltages. However, the
inductor-ripple current also impacts transient-response
performance, especially at low V
Low inductor values allow the inductor current to slew
faster, replenishing charge removed from the output filter
capacitors by a sudden load step.
V
RIPPLE
High-Efficiency, 12A, Current-Mode Synchronous
RIPPLE(ESL)
LX
Step-Down Regulator with Integrated Switches
V
RIPPLE (ESL)
=
swings from V
∆
RIPPLE(C)
V
V
RIPPLE(C)
I
V
P P
RIPPLE(C)
RIPPLE(ESR)
−
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can be approximated as an inductive
=
RIPPLE(ESR)
(
Output Capacitor Selection
V
IN
=
dominates. When using electro-
+
V
IN
=
−
V
LX
RIPPLE(ESR)
8 C
V
to GND.
= ∆
OUT
L f
×
×
×
ESL
I
∆
dominates. Use ceramic
P P
OUT
L
SW
IN
)
I
−
P P
× 
−


to V
=
×
V
×
V
ESR
P-P
V
OUT
f
IN
SW
IN
+
OUT
) is:
×
V
RIPPLE(ESL)



ESL
L
differentials.
Load-transient response also depends on the selected
output capacitance. During a load transient, the output
instantly changes by ESR x ∆I
can respond, the output deviates further, depending on
the inductor and output capacitor values. After a short
time, the controller responds by regulating the output
voltage back to the predetermined value.
Use higher C
light-load operation or transition between heavy load and
light load, triggering skip mode, causing output under-
shooting or overshooting. When applying the load, limit
the output undershooting by sizing C
the following formula:
where ∆I L
gain bandwidth (or zero-crossing frequency), and ∆V
is the desired output undershooting. When removing the
load and entering skip mode, the device cannot control
output overshooting, since it has no sink current capabil-
ity; see the
section to properly size C
A worst-case analysis in sizing the minimum output
capacitance takes the total energy stored in the inductor
into account, as well as the allowable sag/soar (under-
shoot/overshoot) voltage as follows:
where I
values of the load current during the worst-case load
dump, V
V
is the allowed voltage soar (overshoot) above V
V
(V
mum/minimum transient output voltage reached during
the transient, respectively.
Use these equations for initial output-capacitor selection.
Determine final values by testing a prototype or an evalu-
ation circuit under the worst-case conditions.
C
C
FIN
SAG
FIN
OUT (MIN)
OUT(MIN)
is the steady-state voltage after the transient, V
is the allowable voltage sag below V
+ V
OUT(MAX)
INIT
SOAR
OAD
=
=
L
L
Skip Mode Frequency and Output Ripple
×
×
(
is the initial voltage prior to the transient,
V
V
(
OUT
(
I
I
2
FIN
is the total load change, f
2
) and (V
2
INIT
OUT MAX
OUT MAX
C
+
and I
OUT
V
−
(
values for applications that require
(
SOAR
(
V
FIN
=
)
)
OUT(MIN)
FIN
−
−
)
3f
−
OUT
2
I
I
2
2
V
CO
−
OUT MIN
OUT MIN
SAG
- V
∆
V
LOAD
I
2
under this circumstance.
LOAD
(
× ∆
(
INIT
SAG
)
MAX15112
2
are the initial and final
V
)
)
)
)
OUT
) represent the maxi-
. Before the controller
, voltage sag (undershoot)
, voltage soar (overshoot)
OUT
CO
FIN
according to
is the unity-
. The terms
FIN
SOAR
, and
OUT