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PDF LT3012B Data sheet ( Hoja de datos )
| Número de pieza | LT3012B | |
| Descripción | 4V to 80V Low Dropout Micropower Linear Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT3012B
250mA, 4V to 80V
Low Dropout
Micropower Linear Regulator
FEATURES
■ Wide Input Voltage Range: 4V to 80V
■ Low Quiescent Current: 40µA
■ Low Dropout Voltage: 400mV
■ Output Current: 250mA
■ No Protection Diodes Needed
■ Adjustable Output from 1.24V to 60V
■ Stable with 3.3µF Output Capacitor
■ Stable with Aluminum, Tantalum or Ceramic
Capacitors
■ Reverse-Battery Protection
■ No Reverse Current Flow from Output to Input
■ Thermal Limiting
■ Thermally Enhanced 16-Lead TSSOP and 12-Pin
(4mm × 3mm) DFN Packages
U
APPLICATIO S
■ Low Current High Voltage Regulators
■ Regulator for Battery-Powered Systems
■ Telecom Applications
■ Automotive Applications
DESCRIPTIO
The LT®3012B is a high voltage, micropower low dropout
linear regulator. The device is capable of supplying 250mA
of output current with a dropout voltage of 400mV. De-
signed for use in battery-powered or high voltage sys-
tems, the low quiescent current (40µA operating) makes
the LT3012B an ideal choice. Quiescent current is also well
controlled in dropout.
Other features of the LT3012B include the ability to oper-
ate with very small output capacitors. The regulators are
stable with only 3.3µF on the output while most older
devices require between 10µF and 100µF for stability.
Small ceramic capacitors can be used without any need for
series resistance (ESR) as is common with other regula-
tors. Internal protection circuitry includes reverse-battery
protection, current limiting, thermal limiting and reverse
current protection.
The device is available with an adjustable output with a
1.24V reference voltage. The LT3012B regulator is avail-
able in the 16-lead TSSOP and 12 pin low profile (0.75mm)
(4mm × 3mm) DFN packages with an exposed pad for
enhanced thermal handling capability.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
VIN
5.4V TO
80V
5V Supply
IN OUT
LT3012B
1µF
ADJ
GND
750k
VOUT
5V
250mA
3.3µF
249k
3012B TA01
400
350
300
250
200
150
100
50
0
0
Dropout Voltage
50 100 150 200
OUTPUT CURRENT (mA)
250
3012B TA02
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TYPICAL PERFOR A CE CHARACTERISTICS
LT3012B
ADJ Pin Bias Current
50
45
40
35
30
25
20
15
10
5
0
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
3012B G13
Current Limit
1000
VOUT = 0V
900
800
700 TJ = 25°C
600
TJ = 125°C
500
400
300
200
100
0
0 10 20 30 40 50 60
INPUT VOLTAGE (V)
70 80
3012B G14
Current Limit
700
600
500
400
300
200
100 VIN = 7V
0 VOUT = 0V
–50 –25 0
25 50
75
TEMPERATURE (°C)
100 125
3012B G15
Reverse Output Current
200
TJ = 25°C
180 VIN = 0V
160 VOUT = VADJ
140
120
100 CURRENT FLOWS
80 INTO OUTPUT PIN
60
ADJ
PIN CLAMP
(SEE APPLICATIONS
INFORMATION)
40
20
0
0 1 2 3 4 5 6 7 8 9 10
OUTPUT VOLTAGE (V)
3012B G16
Reverse Output Current
35
VIN = 0V
30 VOUT = VADJ = 1.24V
25
20
15
10
5
0
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
3012B G17
Input Ripple Rejection
92
88
84
80
76
72
68
VIN = 4.5V + 0.5VP-P RIPPLE AT f = 120Hz
64 IL = 250mA
VOUT = 1.24V
60
–50 –25 0 25 50 75 100 125
TEMPERATURE (°C)
3012B G18
Input Ripple Rejection
100
VIN = 4.5V + 50mVRMS RIPPLE
90 ILOAD = 250mA
80
70
60
50
COUT = 10µF
40
30
20
10 COUT = 3.3µF
0
10 100 1k 10k 100k 1M
FREQUENCY (Hz)
3012B G19
Minimum Input Voltage
4.0
ILOAD = 250mA
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
– 50 – 25
0 25 50 75
TEMPERATURE (°C)
100 125
3012B G20
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LT3012B
APPLICATIO S I FOR ATIO
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
TJMAX = 50°C + 65.5°C = 115.5°C
Example 2: Given an output voltage of 5V, an input voltage
of 48V that rises to 72V for 5ms(max) out of every 100ms,
and a 5mA load that steps to 50mA for 50ms out of every
250ms, what is the junction temperature rise above ambi-
ent? Using a 500ms period (well under the time constant
of the board), power dissipation is as follows:
P1(48V in, 5mA load) = 5mA • (48V – 5V)
+ (200µA • 48V) = 0.23W
P2(48V in, 50mA load) = 50mA • (48V – 5V)
+ (1mA • 48V) = 2.20W
P3(72V in, 5mA load) = 5mA • (72V – 5V)
+ (200µA • 72V) = 0.35W
P4(72V in, 50mA load) = 50mA • (72V – 5V)
+ (1mA • 72V) = 3.42W
Operation at the different power levels is as follows:
76% operation at P1, 19% for P2, 4% for P3, and
1% for P4.
PEFF = 76%(0.23W) + 19%(2.20W) + 4%(0.35W)
+ 1%(3.42W) = 0.64W
With a thermal resistance in the range of 40°C/W to
62°C/W, this translates to a junction temperature rise
above ambient of 26°C to 38°C.
Protection Features
The LT3012B incorporates several protection features
which make it ideal for use in battery-powered circuits. In
addition to the normal protection features associated with
monolithic regulators, such as current limiting and ther-
mal limiting, the device is protected against reverse-input
voltages, and reverse voltages from output to input.
Current limit protection and thermal overload protection
are intended to protect the device against current overload
conditions at the output of the device. For normal opera-
tion, the junction temperature should not exceed 125°C.
The input of the device will withstand reverse voltages of
80V. No negative voltage will appear at the output. The
device will protect both itself and the load. This provides
protection against batteries which can be plugged in
backward.
The ADJ pin of the device can be pulled above or below
ground by as much as 7V without damaging the device. If
the input is left open circuit or grounded, the ADJ pin will
act like an open circuit when pulled below ground, and like
a large resistor (typically 100k) in series with a diode when
pulled above ground. If the input is powered by a voltage
source, pulling the ADJ pin below the reference voltage
will cause the device to current limit. This will cause the
output to go to a unregulated high voltage. Pulling the ADJ
pin above the reference voltage will turn off all output
current.
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT3012B.PDF ] | |
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