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PDF LTC1911-1.8 Data sheet ( Hoja de datos )
| Número de pieza | LTC1911-1.8 | |
| Descripción | Inductorless Step-Down DC/DC Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1911-1.5/LTC1911-1.8
Low Noise, High Efficiency,
Inductorless Step-Down
DC/DC Converter
FEATURES
s Low Noise Constant Frequency Operation
s 2.7V to 5.5V Input Voltage Range
s No Inductors
s Typical Efficiency 25% Higher Than LDOs
s Shutdown Disconnects Load from VIN
s Output Voltage: 1.8V ±4% or 1.5V ±4%
s Output Current: 250mA
s Low Operating Current: IIN = 180µA Typ
s Low Shutdown Current: IIN = 10µA Typ
s Oscillator Frequency: 1.5MHz
s Soft-Start Limits Inrush Current at Turn On
s Short-Circuit and Overtemperature Protected
s Available in an 8-Pin MSOP Package
U
APPLICATIO S
s Handheld Computers
s Cellular Phones
s Smart Card Readers
s Portable Electronic Equipment
s Handheld Medical Instruments
s Low Power DSP Supplies
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
*U.S. Patent #6,438,005
DESCRIPTIO
The LTC®1911 is a switched capacitor step-down DC/DC
converter that produces a 1.5V or 1.8V regulated output
from a 2.7V to 5.5V input. The part uses switched capaci-
tor fractional conversion to achieve high efficiency over the
entire input range. No inductors are required. Internal cir-
cuitry controls the step-down conversion ratio to optimize
efficiency as the input voltage and load conditions vary.*
Typical efficiency is over 25% higher than that of a linear
regulator.
A unique constant frequency architecture provides a low
noise regulated output as well as lower input noise than
conventional charge pump regulators. High frequency
operation (fOSC = 1.5MHz) simplifies output filtering to
further reduce conducted noise. To optimize efficiency,
the part enters Burst Mode® operation under light load
conditions.
Low operating current (180µA with no load, 10µA in
shutdown) and low external parts count (two 1µF flying
capacitors and two 10µF bypass capacitors) make the
LTC1911 ideally suited for space constrained battery-
powered applications. The part is short-circuit and
overtemperature protected, and is available in an 8-pin
MSOP package.
TYPICAL APPLICATIO
Single Cell Li-Ion to 1.8V DC/DC Converter
2.7V TO 5.5V INPUT
1-CELL Li-Ion
OR
3-CELL NiMH
10µF*
1µF*
*CERAMIC CAPACITOR
LTC1911-1.8
1 VIN SS/SHDN 8
2 C2+
6
VOUT
3 C2–
C1+ 7
4 GND
C1– 5
1µF*
VOUT = 1.8V
IOUT = 250mA
10µF*
1911 TA01
Efficiency
90
80
100mA
70
250mA
60
50
IDEAL LDO
40
VOUT = 1.8V
30
23
4
5
INPUT VOLTAGE (V)
6
1911 G05
1911f
1
1 page  
SI PLIFIED BLOCK DIAGRA
LTC1911-1.5/LTC1911-1.8
VIN
1
CIN
300k
50k
150k
SHDN
+
–
+
–
ADJ
OFFSET
+
–
VREF
RA
MODE
CONTROL
COMP1
–
C1+
7
STEP-DOWN
CHARGE
PUMP
C1–
5
C2+
2
+
AMP1
–
C2–
3
RSENSE VOUT
6
C1
C2
COUT
OVERTEMP
DETECT
+
COMP2
+
–
BURST
THRESHOLD
SHORT-CIRCUIT
THRESHOLD
60k
VIN
2µA
SS/SHDN
8
+
600mV
+
–
1.5MHz
OSCILLATOR
600mV
+
SHDN
–
+
–
AMP2
+
SOFT-START VREF RAMP
140k
1.26V
VREF
GND
4
1911 BD
1911f
5
5 Page 
PACKAGE DESCRIPTIO
LTC1911-1.5/LTC1911-1.8
MS8 Package
8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 ± 0.127
(.035 ± .005)
5.23
(.206)
MIN
3.2 – 3.45
(.126 – .136)
0.42 ± 0.04
(.0165 ± .0015)
TYP
0.65
(.0256)
BSC
RECOMMENDED SOLDER PAD LAYOUT
3.00 ± 0.102
(.118 ± .004)
(NOTE 3)
8 7 65
0.52
(.206)
REF
0.254
(.010)
DETAIL “A”
0° – 6° TYP
4.88 ± 0.1
(.192 ± .004)
3.00 ± 0.102
(.118 ± .004)
NOTE 4
GAUGE PLANE
0.53 ± 0.015
(.021 ± .006)
DETAIL “A”
1 234
1.10
(.043)
MAX
0.18
(.077)
SEATING
PLANE 0.22 – 0.38
(.009 – .015)
0.65
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
(.0256)
BCS
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.86
(.034)
REF
0.13 ± 0.05
(.005 ± .002)
MSOP (MS8) 0102
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
1911f
11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC1911-1.8.PDF ] | |
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