MAX15046BEVKIT+ Maxim Integrated Products, MAX15046BEVKIT+ Datasheet - Page 15
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MAX15046BEVKIT+
Manufacturer Part Number
MAX15046BEVKIT+
Description
KIT FOR MAX1504 SYNC BUCK CTLR
Manufacturer
Maxim Integrated Products
Specifications of MAX15046BEVKIT+
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Connect an external resistor (R
to adjust the current-limit threshold, which is temper-
ature-compensated with a temperature coefficient of
2300ppm/NC. The relationship between the current-limit
threshold (V
where R
NC.
An R
to a current-limit threshold of 30mV to 300mV. Use 1%
tolerance resistors when adjusting the current limit to
minimize error in the current-limit threshold.
The input filter capacitor reduces peak current drawn
from the power source and reduces noise and voltage
ripple on the input caused by the switching circuitry. The
input capacitor must meet the ripple current requirement
(I
the following equation:
I
age equals twice the output voltage (V
so I
nontantalum capacitors (ceramic, aluminum, polymer, or
OS-CON) are preferred at the inputs due to the robust-
ness of nontantalum capacitors to accommodate high
inrush currents of systems being powered from very low
impedance sources. Additionally, two (or more) smaller-
value low-ESR capacitors should be connected in paral-
lel to reduce high-frequency noise.
The key selection parameters for the output capacitor
are capacitance value, ESR, and voltage rating. These
parameters affect the overall stability, output ripple volt-
age, and transient response. The output ripple has two
components: variations in the charge stored in the output
capacitor, and the voltage drop across the capacitor’s
ESR caused by the current flowing into and out of the
capacitor:
RMS
RMS
R
RMS(MAX)
LIM
LIM
) imposed by the switching currents as defined by
attains a maximum value when the input volt-
LIM
=
I
resistance range of 6kI to 60kI corresponds
RMS
50 10
ITH
is in I, V
×
=
) and R
= I
DV
I
LOAD(MAX)
______________________________________________________________________________________
-6
RIPPLE
LOAD(MAX)/2
×
ITH
LIM
1 2300
+
= DV
40V, High-Performance, Synchronous
is in V, T
is:
10 V
V
ESR
×
OUT
. For most applications,
ppm
°
LIM
ITH
C
Output Capacitor
MAX
(V
+ DV
V
) from LIM to GND
×
Input Capacitor
IN
IN
(T
- V
Q
MAX
and T
OUT
IN
- T
AMB
= 2V
)
AMB)
are in
OUT
),
The output-voltage ripple as a consequence of the ESR
and the output capacitance is:
where I
(see the Inductor Selection section). Use these equa-
tions for initial capacitor selection. Decide on the final
values by testing a prototype or an evaluation circuit.
Check the output capacitor against load-transient
response requirements. The allowable deviation of the
output voltage during fast load transients determines
the capacitor output capacitance, ESR, and equivalent
series inductance (ESL). The output capacitor supplies
the load current during a load step until the controller
responds with a higher duty cycle. The response time
(t
the converter (see the Compensation Design section).
The resistive drop across the ESR of the output capaci-
tor, the voltage drop across the ESL (DV
capacitor, and the capacitor discharge, cause a voltage
droop during the load step.
Use a combination of low-ESR tantalum/aluminum elec-
trolytic and ceramic capacitors for improved transient
load and voltage ripple performance. Nonleaded capac-
itors and capacitors in parallel help reduce the ESL.
Keep the maximum output-voltage deviation below the
tolerable limits of the load. Use the following equations to
calculate the required ESR, ESL, and capacitance value
during a load step:
where I
load step, t
ler, and f
RESPONSE
STEP
P-P
O
RESPONSE
is the closed-loop crossover frequency.
is the peak-to-peak inductor current ripple
) depends on the closed-loop bandwidth of
is the load step, t
I
∆
∆
ESR
C
ESL
t
P-P
RESPONSE
V
V
OUT
ESR
Q
Buck Controller
=
=
=
=
8 C
∆
=
∆
=
V
I
STEP
V
is the response time of the control-
×
IN
V
I
f
I
P-P
SW
ESL
ESR
STEP
- V
I
OUT
STEP
I
≅
P-P
×
×
OUT
×
ESR
3 f
L
×
t
×
×
STEP
∆
STEP
t
1
RESPONSE
V
f
O
SW
Q
×
is the rise time of the
V
V
OUT
IN
ESL
) of the
15