LT3587
APPLICATIONS INFORMATION
Lower Input Voltage Applications
the LT3587. The outputs can be driven straight from the
battery, resulting in higher efficiency.
The LT3587 can be used in lower input voltage applica-
tions. The V supply voltage to the LT3587 must be
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.
IN
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
LED DRIVER
20mA UP TO 12V
C4
2AA CELLS
2V TO 3.2V
1μF
L4
10μH
L1
15μH
R
VFB3
D
S3
787k
(OPTIONAL)
D
S1
C1
4.7μF
V
V
CAP3
SW3
SW1
FB3 OUT3
R
IFB3
8.06k
I
CAP1
FB3
C
FB1
3.3pF
FLT
LT3587
EN/SS1
EN/SS3
R
FB1
787k
FB1
V
V
OUT1
SW2
GND
FB2
IN
CCD POSITIVE
12V, 10mA
3.3V
C6
1μF
L2
15μH
C
FB2
R
1M
FB2
C2
2.2μF
6.8pF
L3
15μH
CCD NEGATIVE
–8V, 20mA
2AA CELLS
2V TO 3.2V
D
C7
10μF
S2
3587 F17
C1: MURATA GRM21BR61E475KA12L
C2: MURATA GRM188R61C225KE15D
C4: MURATA GRM188R61E105KA12B
C6: MURATA GRM155R61A105KE15D
C7: MURATA GRM21BR71A106KE51L
C
C
: MURATA GRM1555C1H3R3BZ01D
: MURATA GRM1555C1H6R3BZ01D
FB1
FB2
L1, L2, L3: SUMIDA CDRH2D18/HP-150N
L4: TOKO 1071AS-100M
D
, D , D : NXP PMEG2005EB
S1 S2 S3
Figure 17. 2 AA Cells Providing CCD Positive and Negative Supply
and a Three White Backlight LED Driver
3587fc
19
Linear [ Linear ]
