LT3587 데이터 시트보기 (PDF) - Linear Technology
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LT3587 Datasheet PDF : 24 Pages
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LT3587
APPLICATIONS INFORMATION
Lower Input Voltage Applications
The LT3587 can be used in lower input voltage applica-
tions. The VIN supply voltage to the LT3587 must be
2.5V to 6V. However, the inductors can be run off a lower
voltage. This allows the outputs to be powered off two
alkaline cells. Most portable devices and systems have
a 3.3V logic supply voltage which can be used to power
the LT3587. The outputs can be driven straight from the
battery, resulting in higher efficiency.
Figure 17 shows a typical digital still camera application
with CCD positive and negative supply as well as an LED
driver powered by two AA cells. The battery is connected
to the input inductors and the chip is powered with a 3.3V
logic supply voltage.
LED DRIVER
20mA UP TO 12V
RVFB3
787k
(OPTIONAL)
C4
1μF
L4
DS3
10μH
L1
15μH
2AA CELLS
2V TO 3.2V
RIFB3
8.06k
VFB3 VOUT3 CAP3
IFB3
SW3
FLT
EN/SS1
LT3587
EN/SS3
SW1
CAP1
DS1 C1
4.7μF
CFB1
3.3pF
RFB1
787k
FB1
3.3V
2AA CELLS
2V TO 3.2V
VIN
C6
1μF
L2
15μH
SW2
GND
C2
2.2μF
L3
15μH
DS2
FB2 VOUT1
RFB2
1M
CCD POSITIVE
12V, 10mA
CFB2
6.8pF
C7
10μF
CCD NEGATIVE
–8V, 20mA
3587 F17
C1: MURATA GRM21BR61E475KA12L
C2: MURATA GRM188R61C225KE15D
C4: MURATA GRM188R61E105KA12B
C6: MURATA GRM155R61A105KE15D
C7: MURATA GRM21BR71A106KE51L
CFB1: MURATA GRM1555C1H3R3BZ01D
CFB2: MURATA GRM1555C1H6R3BZ01D
L1, L2, L3: SUMIDA CDRH2D18/HP-150N
L4: TOKO 1071AS-100M
DS1, DS2, DS3: NXP PMEG2005EB
Figure 17. 2 AA Cells Providing CCD Positive and Negative Supply
and a Three White Backlight LED Driver
3587fc
19
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