MAX15062 Datasheet, PDF (17/23 Pages) Maxim Integrated Products – Step-Down DC-DC Converters

MAX15062
60V, 300mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converters
Table 1. Inductor Selection
INPUT VOLTAGE
RANGE V_IN (V)
4.5 to 60
6 to 60
4.5 to 60
14 to 60
17 to 60
V_OUT (V)
3.3 (Fixed)
5 (Fixed)
1.8 or 2.5
12
15
I_OUT (mA)
300
300
300
300
300
L (µH)
33
47
22
100
150
Table 2. Output Capacitor Selection
INPUT VOLTAGE
RANGE V_IN (V)
4.5 to 60
6 to 60
4.5 to 60
14 to 60
17 to 60
V_OUT (V)
3.3 (Fixed)
5 (Fixed)
1.8 or 2.5
12
15
I_OUT (mA)
300
300
300
300
300
C_OUT (µF)
10µF/1206/X7R/6.3V
10µF/1206/X7R/6.3V
22µF/1206/X7R/6.3V
4.7µF/1206/X7R/16V
4.7µF/1206/X7R/25V
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VIN
V_IN
R1
MAX15062
EN/UVLO
R2
Figure 1. Adjustable EN/UVLO Network
Input Capacitor
Small ceramic capacitors are recommended for the
device. The input capacitor reduces peak current drawn
from the power source and reduces noise and voltage
ripple on the input caused by the switching circuitry. A
minimum of 1µF, X7R-grade capacitor in a package larger
than 0805 is recommended for the input capacitor of the
device to keep the input voltage ripple under 2% of the
minimum input voltage, and to meet the maximum ripple-
current requirements.
Output Capacitor
Small ceramic X7R-grade capacitors are sufficient and
recommended for the device. The output capacitor has
two functions. It filters the square wave generated by the
device along with the output inductor. It stores sufficient
energy to support the output voltage under load transient
conditions and stabilizes the device’s internal control loop.
Usually the output capacitor is sized to support a step
load of 50% of the maximum output current in the appli-
cation, such that the output-voltage deviation is less than
3%. The device requires a minimum of 10µF capacitance
for stability. Required output capacitance can be calcu-
lated from the following equation:
C _OUT
=
30
V_OUT
where C_OUT is the output capacitance in µF and V_OUT
is the output voltage. See Table 2 to select the output
capacitor for typical applications.
Setting the Input Undervoltage-Lockout Level
The devices offer an adjustable input undervoltage-
lockout level. Set the voltage at which the device turns
on with a resistive voltage-divider connected from V_IN
to GND (see Figure 1). Connect the center node of the
divider to EN/UVLO.
Choose R1 to be 3.3MΩ max, and then calculate R2 as
follows:
R2 = ^{R1× 1.215}
(V_INU - 1.215)
where V_INU is the voltage at which the device is required
to turn on.
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