LM1937 HTC Korea TAEJIN Technology Co., LM1937 Datasheet - Page 4

• Manufacturer Part Number: LM1937
• Description: White Led Step-up Converter
• Manufacturer: HTC Korea TAEJIN Technology Co.

APPLICATIONS INFORMATION
Inductor Selection
A 22mH inductor is recommended for most LM1937
applications. Although small size and high efficiency are
major concerns, the inductor should have low core
losses at 1.2MHz and low DCR (copper wire resistance).
Some inductors in this category with small size are listed
in Table 1. The efficiency comparison of different
inductors is shown in Figure 3.
Table 1. Recommended Inductors
Figure 3. Efficiency Comparison of Different Inductors
WHITE LED STEP-UP CONVERTER
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Capacitor Selection
The small size of ceramic capacitors makes them
ideal for LM1937 applications. X5R and X7R types are
recommended because they retain their capacitance
over wider voltage and temperature ranges than other
types such as Y5V or Z5U. A 1µF input capacitor and
a 0.22µF output capacitor are sufficient for most
LM1937 applications.
Table 2. Recommended Ceramic Capacitor
Manufacturers
Diode Selection
Schottky diodes, with their low forward voltage drop
and fast reverse recovery, are the ideal choices for
LM1937 applications. The forward voltage drop of a
Schottky diode represents the conduction losses in the
diode, while the diode capacitance (CT or CD)
represents the switching losses. For diode selection,
both forward voltage drop and diode capacitance need
to be considered. Schottky diodes with higher current
ratings usually have lower forward voltage drop and
larger diode capacitance, which can cause significant
switching losses at the 1.2MHz switching frequency of
the LM1937. A Schottky diode rated at 100mA to
200mA is sufficient for most LM1937 applications.
Some recommended Schottky diodes are listed in
Table 3.
Table 3. Recommended Schottky Diodes
LM1937
HTC