LT1949 Ver la hoja de datos (PDF) - Linear Technology
Número de pieza
componentes Descripción
Fabricante
LT1949 Datasheet PDF : 8 Pages
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LT1949
U
OPERATIO
GROUND PLANE
LBI LBO
C1
+
VIN
1
8
R1
2 LT1949
7
L1
R2
3
6
SHUTDOWN
4
5
MULTIPLE
VIAs
GND
C2
VOUT
1949 F04
Figure 4. Recommended Component Placement for Boost
Converter. Note Direct High Current Paths Using Wide PC
Traces. Minimize Trace Area at Pin 1 (VC) and Pin 2 (FB).
Use Multiple Vias to Tie Pin 4 Copper to Ground Plane. Use
Vias at One Location Only to Avoid Introducing Switching
Currents into the Ground Plane
APPLICATIONS INFORMATION
Low-Battery Detector
The LT1949’s low-battery detector is a simple PNP input
gain stage with an open collector NPN output. The nega-
tive input of the gain stage is tied internally to a 200mV
±5% reference. The positive input is the LBI pin. Arrange-
ment as a low-battery detector is straightforward.
R1
LBI
R2
100k
VIN
+
–
LT1949
LBO
3.3V
1M
TO PROCESSOR
200mV
INTERNAL
REFERENCE
GND
1949 F05
R1 = VLB – 200mV
2µA
Figure 5. Setting Low-Battery Detector Trip Point
Figure␣ 5 details hookup. R1 and R2 need only be low
enough in value so that the bias current of the LBI pin
doesn’t cause large errors. For R2, 100k is adequate. The
200mV reference can also be accessed as shown in
Figure␣ 6. The low-battery detector remains active in
shutdown.
200k
2N3906
VREF
200mV
+
10k
10µF
VIN
LBO
LT1949
LBI
GND
1949 F06
Figure 6. Accessing 200mV Reference
6
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