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PDF LT3027 Data sheet ( Hoja de datos )
| Número de pieza | LT3027 | |
| Descripción | Micropower Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
■ Low Noise: 20µVRMS (10Hz to 100kHz)
■ Low Quiescent Current: 25µA/Channel
■ Independent Inputs
■ Wide Input Voltage Range: 1.8V to 20V
■ Output Current: 100mA/Channel
■ Very Low Shutdown Current: <0.1µA
■ Low Dropout Voltage: 300mV at 100mA
■ Adjustable Output from 1.22V to 20V
■ Stable with 1µF Output Capacitor
■ Stable with Aluminum, Tantalum or
Ceramic Capacitors
■ Reverse Battery Protected
■ No Protection Diodes Needed
■ Overcurrent and Overtemperature Protected
■ Thermally Enhanced 10-Lead MSOP and DFN
Packages
U
APPLICATIO S
■ Cellular Phones
■ Pagers
■ Battery-Powered Systems
■ Frequency Synthesizers
■ Wireless Modems
LT3027
Dual 100mA,
Low Dropout, Low Noise,
Micropower Regulator with
Independent Inputs
DESCRIPTIO
The LT®3027 is a dual, micropower, low noise, low drop-
out regulator with independent inputs. With an external
0.01µF bypass capacitor, output noise is a low 20µVRMS
over a 10Hz to 100kHz bandwidth. Designed for use in
battery-powered systems, the low 25µA quiescent current
per channel makes it an ideal choice. In shutdown, quies-
cent current drops to less than 0.1µA. Shutdown control
is independent for each channel, allowing for flexibility in
power management. The device is capable of operating
over an input voltage from 1.8V to 20V, and can supply
100mA of output current from each channel with a drop-
out voltage of 300mV. Quiescent current is well controlled
in dropout.
The LT3027 regulator is stable with output capacitors as
low as 1µF. Small ceramic capacitors can be used without
the series resistance required by other regulators.
Internal protection circuitry includes reverse battery pro-
tection, current limiting and thermal limiting protection.
The device is available as an adjustable device with a
1.22V reference voltage. The LT3027 regulator is available
in the thermally enhanced 10-lead MSOP and low profile
(0.75mm) 3mm × 3mm DFN packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Protected by U.S. Patents, including 6118263, 6144250.
TYPICAL APPLICATIO
3.3V/2.5V Low Noise Regulators
VIN1
3.7V TO
20V
VIN2
2.9V TO
20V
IN1 OUT1
1µF SHDN1
BYP1
ADJ1
LT3027
IN2 OUT2
1µF SHDN2
BYP2
ADJ2
GND
0.01µF 422k
249k
0.01µF 261k
249k
3.3V AT 100mA
20µVRMS NOISE
10µF
2.5V AT 100mA
20µVRMS NOISE
10µF
3027 TA01
10Hz to 100kHz Output Noise
VOUT
100µV/DIV
20µVRMS
3027 TA01b
3027f
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LT3027
SHDN1 or SHDN2 Pin Threshold
(Off-to-On)
1.0
0.9
0.8 IL = 100mA
0.7
0.6 IL = 1mA
0.5
0.4
0.3
0.2
0.1
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
3027 G10
SHDN1 or SHDN2 Pin Input
Current
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 1 2 3 4 5 6 7 8 9 10
SHDN PIN VOLTAGE (V)
3027 G11
SHDN1 or SHDN2 Pin Input
Current
1.4
VSHDN = 20V
1.2
1.0
0.8
0.6
0.4
0.2
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3027 G12
ADJ1 or ADJ2 Pin Bias Current
100
90
80
70
60
50
40
30
20
10
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
3027 G13
Current Limit
350
VOUT = 0V
300 TJ = 25°C
250
200
150
100
50
0
01
2 34
5
INPUT VOLTAGE (V)
67
3027 G14
Current Limit
350
300
VIN = 7V
VOUT = 0V
250
200
150
100
50
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3027 G15
Input Ripple Rejection
80
70
60
50
COUT = 10µF
40
30
20
10
IL = 100mA
VIN = 2.3V + 50mVRMS RIPPLE
0 CBYP = 0
0.01 0.1 1 10
COUT = 1µF
100 1000
FREQUENCY (kHz)
3027 G18
Input Ripple Rejection
80
70 CBYP = 0.01µF
60
CBYP = 1000pF
50 CBYP = 100pF
40
30
20
10
IL = 100mA
VIN = 2.3V + 50mVRMS RIPPLE
0 COUT = 10µF
0.01 0.1 1 10
FREQUENCY (kHz)
100 1000
3027 G19
3027f
5
5 Page 
LT3027
APPLICATIO S I FOR ATIO
Voltage and temperature coefficients are not the only
sources of problems. Some ceramic capacitors have a
piezoelectric response. A piezoelectric device generates
voltage across its terminals due to mechanical stress,
similar to the way a piezoelectric accelerometer or
microphone works. For a ceramic capacitor the stress
can be induced by vibrations in the system or thermal
transients. The resulting voltages produced can cause
appreciable amounts of noise, especially when a ceramic
capacitor is used for noise bypassing. A ceramic capaci-
tor produced Figure 5’s trace in response to light tapping
from a pencil. Similar vibration induced behavior can
masquerade as increased output voltage noise.
COUT = 10µF
CBYP = 0.01µF
ILOAD = 100mA
VOUT
500µV/DIV
100ms/DIV
3027 F05
Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor
Thermal Considerations
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be made up of two
components (for each channel):
1. Output current multiplied by the input/output voltage
differential: (IOUT)(VIN – VOUT), and
2. GND pin current multiplied by the input voltage:
(IGND)(VIN).
The ground pin current can be found by examining the
GND Pin Current curves in the Typical Performance
Characteristics section. Power dissipation will be equal to
the sum of the two components listed above. Power
dissipation from both channels must be considered dur-
ing thermal analysis.
The LT3027 regulator has internal thermal limiting de-
signed to protect the device during overload conditions.
For continuous normal conditions, the maximum junction
temperature rating of 125°C must not be exceeded. It is
important to give careful consideration to all sources of
thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
and its copper traces. Copper board stiffeners and plated
through-holes can also be used to spread the heat gener-
ated by power devices.
The following tables list thermal resistance for several
different board sizes and copper areas. All measurements
were taken in still air on 3/32" FR-4 board with one ounce
copper.
Table 1. MSE Package, 10-Lead MSOP
COPPER AREA
THERMAL RESISTANCE
TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
2500mm2
1000mm2
225mm2
100mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
40°C/ W
45°C/ W
50°C/ W
62°C/ W
*Device is mounted on topside.
Table 2. DD Package, 10-Lead DFN
COPPER AREA
THERMAL RESISTANCE
TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
2500mm2
1000mm2
225mm2
100mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
2500mm2
40°C/ W
45°C/ W
50°C/ W
62°C/ W
*Device is mounted on topside.
The thermal resistance juncton-to-case (θJC), measured
at the Exposed Pad on the back of the die is 10°C/W.
Calculating Junction Temperature
Example: Given an output voltage on the first channel of
3.3V, an output voltage of 2.5V on the second channel, an
input voltage range of 4V to 6V, output current ranges of
0mA to 100mA for the first channel and 0mA to 50mA for
the second channel, with a maximum ambient tempera-
ture of 50°C, what will the maximum junction temperature
be?
3027f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT3027.PDF ] | |
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