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PDF LT3008 Data sheet ( Hoja de datos )
| Número de pieza | LT3008 | |
| Descripción | 45V Low Dropout Linear Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT3008
3µA IQ, 20mA, 45V
Low Dropout Linear Regulator
FEATURES
n Ultralow Quiescent Current: 3μA
n Input Voltage Range: 2.0V to 45V
n Output Current: 20mA
n Dropout Voltage: 300mV
n Adjustable Output (VADJ = VOUT(MIN) = 600mV)
n Output Tolerance: ±2% Over Load, Line and
Temperature
n Stable with Low ESR, Ceramic Output Capacitors
(2.2μF minimum)
n Shutdown Current: <1μA
n Current Limit Protection
n Reverse-Battery Protection
n Thermal Limit Protection
n TSOT-23 and 2mm × 2mm DFN Packages
APPLICATIONS
n Automotive
n Low Current Battery-Powered Systems
n Keep-Alive Power Supplies
n Remote Monitoring
n Utility Meters
n Low Power Industrial Applications
DESCRIPTION
The LT®3008 is a micropower, low dropout voltage (LDO)
linear regulator. The device supplies 20mA output current
with a dropout voltage of 300mV. No-load quiescent cur-
rent is 3μA. Ground pin current remains at less than 5% of
output current as load increases. In shutdown, quiescent
current is less than 1μA.
The LT3008 regulator optimizes stability and transient
response with low ESR ceramic capacitors, requiring a
minimum of only 2.2μF. The LT3008 does not require
the addition of ESR as is common with other regulators.
Internal protection circuitry includes current limiting,
thermal limiting, reverse-battery protection and reverse-
current protection.
The LT3008 is ideal for applications that require moderate
output drive capability coupled with ultralow standby power
consumption. The device is available as an adjustable
device with an output voltage range down to the 600mV
reference. The LT3008 is available in the 6-lead DFN and
8-lead TSOT-23 packages.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
3.3V, 20mA Supply with Shutdown
VIN
3.8V TO
45V
VOUT
IN OUT
3.3V
1μF
LT3008
2.8M
1%
2.2μF 20mA
SHDN ADJ
GND
619k
1%
3008 TA01a
Dropout Voltage/Quiescent Current
500
ILOAD = 20mA
450
400
DROPOUT
VOLTAGE
6
5
350 4
300
250 IQ 3
200
2
150
100 1
50
0
–50 –25
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
3008 TA01b
3008f
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LT3008
TYPICAL PERFORMANCE CHARACTERISTICS TJ = 25°C, unless otherwise noted.
Quiescent Current
30
27
24
VOUT = 3.3V
ILOAD = 1μA
21
18
15
12
9
6
3
0
0 2 4 6 8 10 12
INPUT VOLTAGE (V)
3008 G07
GND Pin Current
400
VOUT = 3.3V
350
20mA (RLOAD = 165Ω)
300
250
200
150 10mA (RLOAD = 330Ω)
100 100μA (RLOAD = 33k)
50 1mA (RLOAD = 3.3k)
0
0 1 2 3 4 5 6 7 8 9 10
INPUT VOLTAGE (V)
3008 G08
GND Pin Current vs ILOAD
1000
VIN = 3.8V
VOUT = 3.3V
100
10
1
0.001 0.01
0.1 1
LOAD (mA)
10 100
3008 G09
SHDN Pin Thresholds
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
–50
–25
OFF TO ON
ON TO OFF
0 25 50 75 100 125 150
TEMPERATURE (°C)
3008 G10
SHDN Pin Input Current
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0 5 10 15 20 25 30 35 40 45
SHDN PIN VOLTAGE (V)
3008 G11
SHDN Pin Input Current
2
1.8
1.6
1.4
1.2
1
0.8 VSHDN = 45V
0.6
0.4
0.2
0
–50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
3008 G12
Current Limit
100
90
80 VIN = 45V
70
60
50
40 VIN = 2V
30
20
10
0
–50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
3008 G13
Reverse Output Current
50
OUT = ADJ = 1.2V
45 IN = SHDN = GND
40
35
30
25
20
15
10 ADJ
5
0
–50 –25
OUT
0 25 50 75 100 125 150
TEMPERATURE (°C)
3008 G14
Input Ripple Rejection
90
VIN = 2.1V + 50mVRMS
80 VOUT = 600mV
ILOAD = 20mA
70
60
50
40
30 10μF
20
2.2μF
10
0
10 100 1000 10000 100000 1000000
FREQUENCY (Hz)
3008 G15
3008f
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LT3008
APPLICATIONS INFORMATION
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 two-layer boards with
one ounce copper.
PCB layers, copper weight, board layout and thermal vias
affect the resultant thermal resistance. Although Tables
2 and 3 provide thermal resistance numbers for 2-layer
boards with 1 ounce copper, modern multi-layer PCBs
provide better performance than found in these tables.
For example, a 4-layer, 1 ounce copper PCB board with
3 thermal vias from the DFN exposed backside or the
3 fused TSOT-23 GND pins to inner layer GND planes
achieves 45°C/W thermal resistance. Demo circuit DC
1388A’s board layout achieves this 45°C/W performance.
This is approximately a 30% improvement over the lowest
numbers shown in Tables 2 and 3.
Table 2: Measured Thermal Resistance for DC Package
COPPER AREA
TOPSIDE*
2500mm2
BACKSIDE
2500mm2
BOARD
AREA
2500mm2
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
65°C/W
1000mm2 2500mm2 2500mm2
70°C/W
225mm2
100mm2
2500mm2
2500mm2
2500mm2
2500mm2
75°C/W
80°C/W
50mm2
2500mm2 2500mm2
85°C/W
*Device is mounted on the topside.
Table 3: Measured Thermal Resistance for TSOT-23 Package
COPPER AREA
TOPSIDE*
2500mm2
BACKSIDE
2500mm2
BOARD
AREA
2500mm2
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
65°C/W
1000mm2 2500mm2 2500mm2
67°C/W
225mm2 2500mm2 2500mm2
70°C/W
100mm2 2500mm2 2500mm2
75°C/W
50mm2
2500mm2 2500mm2
85°C/W
*Device is mounted on the topside.
Calculating Junction Temperature
Example: Given an output voltage of 3.3V, an input volt-
age range of 12V ±5%, an output current range of 0mA
to 20mA and a maximum ambient temperature of 85°C,
what will the maximum junction temperature be for an
application using the DC package?
The power dissipated by the device is equal to:
IOUT(MAX) (VIN(MAX) – VOUT) + IGND (VIN(MAX))
where,
IOUT(MAX) = 20mA
VIN(MAX) = 12.6V
IGND at (IOUT = 20mA, VIN = 12.6V) = 0.3mA
So,
P = 20mA(12.6V – 3.3V) + 0.3mA(12.6V) = 189.8mW
The thermal resistance ranges from 65°C/W to 85°C/W
depending on the copper area. So the junction temperature
rise above ambient approximately equals:
0.1898W(75°C/W) = 14.2°C
The maximum junction temperature equals the maximum
junction temperature rise above ambient plus the maximum
ambient temperature or:
TJ(MAX) = 85°C + 14.2°C = 99.2°C
3008f
11
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT3008.PDF ] | |
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