參數(shù)資料
型號: LT1937ES5#TRM
廠商: LINEAR TECHNOLOGY CORP
元件分類: 穩(wěn)壓器
英文描述: 0.32 A SWITCHING REGULATOR, 1600 kHz SWITCHING FREQ-MAX, PDSO5
封裝: PLASTIC, TSOT-23, 5 PIN
文件頁數(shù): 8/12頁
文件大?。?/td> 358K
代理商: LT1937ES5#TRM
5
LT1937
1937f
Inductor Selection
A 22
H inductor is recommended for most LT1937 appli-
cations. 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 4.
Table 1. Recommended Inductors
CURRENT
DCR
RATING
PART NUMBER
(
)
(mA)
MANUFACTURER
LQH3C220
0.71
250
Murata
814-237-1431
www.murata.com
ELJPC220KF
4.0
160
Panasonic
714-373-7334
www.panasonic.com
CDRH3D16-220
0.53
350
Sumida
847-956-0666
www.Sumida.com
LB2012B220M
1.7
75
Taiyo Yuden
408-573-4150
www.t-yuden.com
LEM2520-220
5.5
125
Taiyo Yuden
408-573-4150
www.t-yuden.com
APPLICATIO S I FOR ATIO
WU
UU
Capacitor Selection
The small size of ceramic capacitors makes them ideal for
LT1937 applications. X5R and X7R types are recom-
mended because they retain their capacitance over wider
voltage and temperature ranges than other types such as
Y5V or Z5U. A 1
F input capacitor and a 0.22F output
capacitor are sufficient for most LT1937 applications.
Table 2. Recommended Ceramic Capacitor Manufacturers
MANUFACTURER
PHONE
URL
Taiyo Yuden
408-573-4150
www.t-yuden.com
AVX
843-448-9411
www.avxcorp.com
Murata
814-237-1431
www.murata.com
Kemet
408-986-0424
www.kemet.com
Diode Selection
Schottky diodes, with their low forward voltage drop and
fast reverse recovery, are the ideal choices for LT1937
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 switch-
ing frequency of the LT1937. A Schottky diode rated at
100mA to 200mA is sufficient for most LT1937 applica-
tions. Some recommended Schottky diodes are listed in
Table 3.
Table 3. Recommended Schottky Diodes
FORWARD VOLTAGE
DIODE
PART
CURRENT
DROP
CAPACITANCE
NUMBER
(mA)
(V)
(pF)
MANUFACTURER
CMDSH-3
100
0.58 at
7.0 at
Central
100mA
10V
631-435-1110
www.centralsemi.com
CMDSH2-3
200
0.49 at
15 at
Central
200mA
10V
631-435-1110
www.centralsemi.com
BAT54
200
0.53 at
10 at
Zetex
100mA
25V
631-543-7100
www.zetex.com
Figure 4. Efficiency Comparison of Different Inductors
LOAD CURRENT (mA)
0
EFFICIENCY
(%)
90
85
80
75
70
65
60
55
50
16
1937 F04
4
8
12
20
14
2
6
10
18
MURATA LQH3C-220
PANASONIC ELJPC220KF
SUMIDA CDRH3D16-220
TAIYO YUDEN LB2012B220M
TAIYO YUDEN LEM2520-220
VIN = 3.6V
3LEDs
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