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PDF LT3048 Data sheet ( Hoja de datos )
| Número de pieza | LT3048 | |
| Descripción | Low Noise Bias Generator | |
| Fabricantes | Linear | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT3048 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
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FEATURES
nn Generates Low Noise Bias Voltage from Single
Cell Li-Ion Battery
nn Output Current: Up to 40mA
nn Low Output Ripple and Noise: <500µVP-P
nn Boost Regulator
nn 1MHz Operation (LT3048)
nn 2.2MHz Operation (LT3048-XX)
nn Integrated Schottky Diode
nn Low Dropout Linear Regulator
nn 1.235V Feedback Voltage (LT3048)
nn Low Noise: <120µVRMS (10Hz to 100kHz)
nn 0.1% Load Regulation
nn Fixed 3.3V, 5V, 12V, 15V and Adjustable Output Options
nn Short-Circuit and Thermal Protection
nn Load Disconnect in Shutdown
nn Available in 2mm × 2mm DFN Package
APPLICATIONS
nn Sensor Bias
nn Op Amp Supply
LT3048 Series
Low Noise Bias Generator
in 2mm × 2mm DFN
DESCRIPTION
The LT®3048 series generate low noise, low ripple bias
supplies from input voltages of 2.7V to 4.8V.
The LT3048 includes a boost regulator and a LDO linear
regulator. The boost regulator provides power to the
linear regulator.
The boost regulator output voltage is regulated to 1.1V
above the LDO output, optimizing LDO ripple rejection and
transient response. Fixed frequency operation and current
mode control allow the use of very small inductors and
results in low, predictable output ripple.
The linear regulator in the LT3048 generates a program-
mable output and the LT3048-XX generate fixed output
voltages. High power supply ripple rejection combined
with a low noise internal reference results in less than
500µVP-P output ripple and noise.
The LT3048 is available in a 8-lead 2mm × 2mm DFN
package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
IN
2.7V TO 4.8V
10µH
SW BSTOUT
VIN LDOIN
1µF LT3048-15
LDOOUT
OFF ON
EN BYP
GND
3048 TA01a
4.7µF
OUT
1nF
1µF
15V
VIN (V) IOUT (mA)
2.7 19
3.3 22
3.6 24
Efficiency
80
70
60
50
40
30 LDOOUT = 15V
L = 10µH
20 DCR = 650mΩ
10
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
0
0 5 10 15 20 25
LOAD CURRENT (mA)
3048 TA01b
For more information www.linear.com/LT3048
3048fa
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LT3048 Series
LT3048 FB Voltage
1.260
1.255
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3048 G01
LT3048 FB Load Regulation
1.260
1.255
1.250
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
0
5 10 15 20 25 30 35 40
LOAD CURRENT (mA)
3048 G02
LT3048 LDOOUT Noise
1000
100
10
1
VIN = 3.6V
VOUT = 1.235V
L = 5.6μH
0.1
CBSTOUT = 4.7μF
CLDOOUT = 1μF
CBYP = 1nF
ILOAD = 40mA
0.01
10 100 1k
10k
FREQUENCY (Hz)
100k 1M
3048 G04
LT3048-15 Efficiency
80
70
60
50
40
30 LDOOUT = 15V
L = 10µH
20 DCR = 650mΩ
10
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
0
0 5 10 15 20 25
LOAD CURRENT (mA)
3048 G05
LT3048 Switching Frequency
1.3
1.2
1.1
1.0
0.9
0.8
0.7
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3048 G03
LT3048-15 LDOOUT Load
Regulation
15.3
15.2
15.1
15.0
14.9
14.8
14.7
0
5 10 15 20 25 30 35 40
LOAD CURRENT (mA)
3048 G06
LT3048-15 LDOOUT Voltage
15.3
15.2
15.1
15.0
14.9
14.8
LT3048-15 Transient Response
50
0 VOUT
–50
–100
–150
–200
ILOAD
–250
70
60
50
40
30
20
10
14.7–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3048 G07
–300
VIN = 3.6V
VOUT = 15V
L = 10µH
10µs/DIV
CLDOOUT = 1µF
CBYP = 1nF
ILOAD = 4mA TO 20mA
0
3048 G08
For more information www.linear.com/LT3048
LT3048-15 LDOOUT Noise
10000
1000
100
10
VIN = 3.6V
VOUT = 15V
L = 10μH
1
CBSTOUT = 4.7μF
CLDOOUT = 1μF
CBYP = 1nF
ILOAD = 24mA
0.110 100 1k 10k
FREQUENCY (Hz)
100k 1M
3048 G09
3048fa
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5 Page 
LT3048 Series
APPLICATIONS INFORMATION
45
L = 5.6µH
40 DCR = 120mΩ
35
VIN = 2.7V
VIN = 3.3V
30
VIN = 3.6V
GUARANTEED
25
20
15
10
5
0
0 2 4 6 8 10 12 14 16 18 20 22
LDOOUT VOLTAGE (V)
3048 F02
Figure 2. LT3048 Typical and Guaranteed Load
Current vs. Output Voltage
C1
L1
C2
C4 C3
Reducing Output Noise With A Bypass Capacitor
The LT3048 relies on the power supply rejection of the
linear regulator to reduce switching regulator noise at
LDOOUT. The linear regulator also contributes thermal
noise to the output. The thermal noise can be reduced,
and transient response improved, by adding a capacitor
between LDOOUT and BYP. A typical value is 1nF. This
capacitor increases start-up time of the regulator.
Recommended PCB Layout
Figure 3 shows the recommended layout for LT3048 cir-
cuits. Most important is careful placement of the BSTOUT
bypass capacitor C2. High frequency AC current flows in a
loop formed by C2, internal power transistor Q1 and boost
diode D2. Keep this loop small. Also be sure to place an
unbroken ground plane below this loop, on the highest
copper layer below the surface. This prevents the AC loop
from coupling to LDOOUT and other nearby circuitry. Keep
the SW node as small as possible.
LDO Stability and Output Capacitance
The LT3048 linear regulator requires an output capacitor
for stability. It is designed to be stable with most low
ESR capacitors (typically ceramic, tantalum or low ESR
electrolytic). A minimum output capacitor of 1μF with an
ESR of 1Ω or less is recommended to prevent oscilla-
tions. Larger values of output capacitance decrease peak
Figure 3. Recommended PCB Layout
3048 F03
deviations and provide improved transient response for
larger load current changes. Bypass capacitors, used to
decouple individual components powered by the LT3048,
increase the effective output capacitor value.
Give consideration to the use of ceramic capacitors as
they are manufactured with a variety of dielectrics, each
with different behavior across temperature and applied
voltage. The most common dielectrics used are specified
with EIA codes of Z5U, Y5V, X5R and X7R. Typical volt-
age and temperature coefficients are shown in Figures 4
and 5. The X5R and X7R dielectrics have more stable
characteristics and are most suitable for use as the output
capacitor. The X7R type has better stability across tem-
perature, while the X5R is less expensive and is available
in higher values. Care still must be exercised when using
X5R and X7R capacitors; the codes only specify operating
temperature range and maximum capacitance change
over temperature. Capacitance change due to DC bias
with X5R and X7R capacitors can be significant enough
to drop capacitor values below appropriate levels. Capaci-
tor DC bias characteristics tend to improve as case size
increases, but expected capacitance at operating voltage
should be verified.
For more information www.linear.com/LT3048
3048fa
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT3048.PDF ] | |
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