MAX15062 Datasheet, PDF (18/23 Pages) Maxim Integrated Products – Step-Down DC-DC Converters

MAX15062
60V, 300mA, Ultra-Small, High-Efficiency,
Synchronous Step-Down DC-DC Converters
Adjusting the Output Voltage
The MAX15062C output voltage can be programmed
from 0.9V to 0.89 x V_IN. Set the output voltage by con-
necting a resistor-divider from output to FB to GND (see
Figure 2).
For the output voltages less than 6V, choose R2 in the
50kΩ to 150kΩ range. For the output voltages greater
than 6V, choose R2 in the 25kΩ to 75kΩ range and calcu-
late R1 with the following equation:
R=1
R2
×
 V_OUT
 _0.9
−
1^{}
Power Dissipation
Ensure that the junction temperature of the device does
not exceed 125°C under the operating conditions speci-
fied for the power supply. At a particular operating condi-
tion, the power losses that lead to temperature rise of the
part are estimated as follows:
P_LOSS

= _P_OUT ×




1
η
- 1_{}

-
(I_OUT ²
× R_DCR )
P= _OUT V_OUT × I_OUT
where P_OUT is the output power, η is the efficiency of
power conversion, and R_DCR is the DC resistance of the
output inductor. See the Typical Operating Characteristics
for the power-conversion efficiency or measure the effi-
ciency to determine the total power dissipation.
The junction temperature (T_J) of the device can be esti-
mated at any ambient temperature (T_A) from the following
equation:
T_J= T_A + (θ_JA × P_LOSS)
where θ_JA is the junction-to-ambient thermal impedance
of the package.
PCB Layout Guidelines
Careful PCB layout is critical to achieve clean and stable
operation. The switching power stage requires particular
attention. Follow the guidelines below for good PCB layout.
● Place the input ceramic capacitor as close as possible
to the V_IN and GND pins.
● Connect the negative terminal of the V_CC bypass
capacitor to the GND pin with shortest possible trace or
ground plane.
● Minimize the area formed by the LX pin and the induc-
tor connection to reduce the radiated EMI.
● Place the V_CC decoupling capacitor as close as pos-
sible to the V_CC pin.
● Ensure that all feedback connections are short and
direct.
● Route the high-speed switching node (LX) away from
the FB/V_OUT, RESET, and MODE pins.
For a sample PCB layout that ensures the first-pass
success, refer to the MAX15062 evaluation kit layouts
available at www.maximintegrated.com.
R1
FB
MAX15062C
R2
GND
VOUT
Figure 2. Setting the Output Voltage
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