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PDF LT1963 Data sheet ( Hoja de datos )
| Número de pieza | LT1963 | |
| Descripción | 1.5A/ Low Noise/ Fast Transient Response LDO Regulators | |
| Fabricantes | Linear | |
| Logotipo |  |
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LT1963 Series
1.5A, Low Noise,
Fast Transient Response
LDO Regulators
FEATURES
■ Optimized for Fast Transient Response
■ Output Current: 1.5A
■ Dropout Voltage: 340mV
■ Low Noise: 40µVRMS (10Hz to 100kHz)
■ 1mA Quiescent Current
■ No Protection Diodes Needed
■ Controlled Quiescent Current in Dropout
■ Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3.3V
■ Adjustable Output from 1.21V to 20V
■ < 1µA Quiescent Current in Shutdown
■ Stable with 10µF Output Capacitor
■ Reverse Battery Protection
■ No Reverse Current
■ Thermal Limiting
■ 5-Lead TO-220, DD, 3-Lead SOT-223, 8-Lead SO
and 16-Lead TSSOP Packages
U
APPLICATIO S
■ 3.3V to 2.5V Logic Power Supplies
■ Post Regulator for Switching Supplies
TYPICAL APPLICATION
VIN > 3V
3.3V to 2.5V Regulator
+
10µF
IN OUT
LT1963-2.5
SHDN SENSE
GND
2.5V
+ 1.5A
10µF
1963 TA01
DESCRIPTIO
The LT®1963 series are low dropout regulators optimized
for fast transient response. The devices are capable of
supplying 1.5A of output current with a dropout voltage of
340mV. Operating quiescent current is 1mA, dropping to
< 1µA in shutdown. Quiescent current is well controlled; it
does not rise in dropout as it does with many other
regulators. In addition to fast transient response, the
LT1963 regulators have very low output noise which
makes them ideal for sensitive RF supply applications.
Output voltage range is from 1.21V to 20V. The LT1963
regulators are stable with output capacitors as low as
10µF. Internal protection circuitry includes reverse battery
protection, current limiting, thermal limiting and reverse
current protection. The devices are available in fixed
output voltages of 1.5V, 1.8V, 2.5V, 3.3V and as an
adjustable device with a 1.21V reference voltage. The
LT1963 regulators are available in 5-lead TO-220, DD,
3-lead SOT-223, 8-lead SO, and Exposed Pad 16-lead
TSSOP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 6118263, 6144250.
Dropout Voltage
400
350
300
250
200
150
100
50
0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
OUTPUT CURRENT (A)
1963 TA02
1963fc
1
1 page  
TYPICAL PERFOR A CE CHARACTERISTICS
LT1963 Series
Typical Dropout Voltage
500
450
400
350
300
250
200
150
100
50
0
0
TJ = 125°C
TJ = 25°C
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
OUTPUT CURRENT (A)
1963 • G01
Guaranteed Dropout Voltage
600
TEST POINTS
500
TJ ≤ 125°C
400
TJ ≤ 25°C
300
200
100
0
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
OUTPUT CURRENT (A)
1963 • G02
Dropout Voltage
500
450
400
350
300 IL = 1.5A
250
200 IL = 0.5A
150
100 IL = 100mA
50
0
–50 –25
IL = 1mA
0 25 50 75 100 125
TEMPERATURE (°C)
1963 G03
Quiescent Current
1.4
1.2 LT1963-1.5/-1.8/-2.5/-3.3
1.0
0.8 LT1963
0.6
0.4
0.2
VIN = 6V
RL = ∞, IL = 0
VSHDN = VIN
0
– 50 – 25 0 25 50
75
TEMPERATURE (°C)
100 125
1963 G04
LT1963-1.5 Output Voltage
1.54
IL = 1mA
1.53
1.52
1.51
1.50
1.49
1.48
1.47
1.46
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
1963 G04i
LT1963-1.8 Output Voltage
1.84
IL = 1mA
1.83
1.82
1.81
1.80
1.79
1.78
1.77
1.76
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1963 G05
LT1963-2.5 Output Voltage
2.58
IL = 1mA
2.56
2.54
2.52
2.50
2.48
2.46
2.44
2.42
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1963 G06
LT1963-3.3 Output Voltage
3.38
IL = 1mA
3.36
3.34
3.32
3.30
3.28
3.26
3.24
3.22
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1963 G07
LT1963 ADJ Pin Voltage
1.230
IL = 1mA
1.225
1.220
1.215
1.210
1.205
1.200
1.195
1.190
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1963 G08
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5 Page 
LT1963 Series
APPLICATIO S I FOR ATIO
The LT1963 series are 1.5A low dropout regulators opti-
mized for fast transient response. The devices are capable
of supplying 1.5A at a dropout voltage of 350mV. The low
operating quiescent current (1mA) drops to less than 1µA
in shutdown. In addition to the low quiescent current, the
LT1963 regulators incorporate several protection features
which make them ideal for use in battery-powered sys-
tems. The devices are protected against both reverse input
and reverse output voltages. In battery backup applica-
tions where the output can be held up by a backup battery
when the input is pulled to ground, the LT1963-X acts like
it has a diode in series with its output and prevents reverse
current flow. Additionally, in dual supply applications
where the regulator load is returned to a negative supply,
the output can be pulled below ground by as much as 20V
and still allow the device to start and operate.
Adjustable Operation
The adjustable version of the LT1963 has an output
voltage range of 1.21V to 20V. The output voltage is set by
the ratio of two external resistors as shown in Figure 2. The
device servos the output to maintain the voltage at the ADJ
pin at 1.21V referenced to ground. The current in R1 is
then equal to 1.21V/R1 and the current in R2 is the current
in R1 plus the ADJ pin bias current. The ADJ pin bias
current, 3µA at 25°C, flows through R2 into the ADJ pin.
The output voltage can be calculated using the formula in
Figure 2. The value of R1 should be less than 4.17k to
minimize errors in the output voltage caused by the ADJ
pin bias current. Note that in shutdown the output is turned
off and the divider current will be zero.
IN OUT
VIN LT1963
ADJ
GND
R2 +
VOUT
R1
1963 F02
VOUT = 1.21V⎛⎝⎜1+ RR21⎞⎠⎟ + (IADJ)(R2)
VADJ = 1.21V
IADJ = 3µA AT 25°C
OUTPUT RANGE = 1.21V TO 20V
Figure 2. Adjustable Operation
The adjustable device is tested and specified with the ADJ
pin tied to the OUT pin for an output voltage of 1.21V.
Specifications for output voltages greater than 1.21V will
be proportional to the ratio of the desired output voltage to
1.21V: VOUT/1.21V. For example, load regulation for an
output current change of 1mA to 1.5A is – 3mV typical at
VOUT = 1.21V. At VOUT = 5V, load regulation is:
(5V/1.21V)(–3mV) = – 12.4mV
Output Capacitance and Transient Response
The LT1963 regulators are designed to be stable with a wide
range of output capacitors. The ESR of the output capacitor
affects stability, most notably with small capacitors. A mini-
mum output capacitor of 10µF with an ESR in the range of
50mΩ to 3Ω is recommended to prevent oscillations.Larger
values of output capacitance can decrease the peak devia-
tions and provide improved transient response for larger
load current changes. Bypass capacitors, used to decouple
individual components powered by the LT1963, will in-
crease the effective output capacitor value.
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior across
temperature and applied voltage. The most common di-
electrics used are specified with EIA temperature charac-
teristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V
dielectrics are good for providing high capacitances in a
small package, but they tend to have strong voltage and
temperature coefficients as shown in Figures 2 and 3.
When used with a 5V regulator, a 16V 10µF Y5V capacitor
can exhibit an effective value as low as 1µF to 2µF for the
DC bias voltage applied and over the operating tempera-
ture range. The X5R and X7R dielectrics result in more
stable characteristics and are more suitable for use as the
output capacitor. The X7R type has better stability across
temperature, while the X5R is less expensive and is
available in higher values. Care still must be exercised
when using X5R and X7R capacitors; the X5R and X7R
codes only specify operating temperature range and maxi-
mum capacitance change over temperature. Capacitance
change due to DC bias with X5R and X7R capacitors is
better than Y5V and Z5U capacitors, but can still be
significant enough to drop capacitor values below appro-
priate levels. Capacitor DC bias characteristics tend to
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| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LT1963.PDF ] | |
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