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PDF LT1964ES5-SD Data sheet ( Hoja de datos )
| Número de pieza | LT1964ES5-SD | |
| Descripción | 200mA/ Low Noise/ Low Dropout Negative Micropower Regulator in ThinSOT | |
| Fabricantes | Linear Technology | |
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LT1964
200mA, Low Noise,
Low Dropout Negative
Micropower Regulator in ThinSOT
FEATURES
s Low Profile (1mm) ThinSOTTM Package
s Low Noise: 30µVRMS (10Hz to 100kHz)
s Low Quiescent Current: 30µA
s Low Dropout Voltage: 340mV
s Output Current: 200mA
s Fixed Output Voltage: –5V
s Adjustable Output from –1.22V to – 20V
s Positive or Negative Shutdown Logic
s 3µA Quiescent Current in Shutdown
s Stable with 1µF Output Capacitor
s Stable with Aluminum, Tantalum, or Ceramic
Capacitors
s Thermal Limiting
U
APPLICATIO S
s Battery-Powered Instruments
s Low Noise Regulator for Noise-Sensitive
Instrumentation
s Negative Complement to LT1761 Family of
Positive LDOs
DESCRIPTIO
The LT®1964 is a micropower low noise, low dropout
negative regulator. The device is capable of supplying
200mA of output current with a dropout voltage of 340mV.
Low quiescent current (30µA operating and 3µA shut-
down) makes the LT1964 an excellent choice for battery-
powered applications. Quiescent current is well controlled
in dropout.
Other features of the LT1964 include low output noise.
With the addition of an external 0.01µF bypass capacitor,
output noise is reduced to 30µVRMS over a 10Hz to 100kHz
bandwidth. The LT1964 is capable of operating with small
capacitors and is stable with output capacitors as low as
1µF. Small ceramic capacitors can be used without the
necessary addition of ESR as is common with other
regulators. Internal protection circuitry includes reverse
output protection, current limiting, and thermal limiting.
The device is available with a fixed output voltage of –5V
and as an adjustable device with a –1.22V reference
voltage. The LT1964 regulators are available in a low
profile (1mm) ThinSOT package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
–5V Low Noise Regulator
VIN
–5.4V
TO –20V
1µF
GND
SHDN BYP
LT1964-5
IN OUT
10µF
0.01µF
–5V AT 200mA
30µVRMS NOISE
1964 TA01a
10Hz to 100kHz Output Noise
VOUT
100µV/DIV
30µVRMS
1ms/DIV
1964 TA01b
1964f
1
1 page  
LT1964
TYPICAL PERFOR A CE CHARACTERISTICS
LT1964-BYP, LT1964-SD
GND Pin Current
–3.0
TJ = 25°C; VSHDN = VIN; *FOR VOUT = –1.22V
–2.5
RL = 6.1Ω
IL = –200mA*
–2.0
RL = 12.2Ω
–1.5 IL = –100mA*
RL = 24.4Ω
–1.0 IL = –50mA*
RL = 122Ω
–0.5 IL = –10mA*
0
0 –1 –2 –3 –4 –5 –6 –7 –8 –9 –10
INPUT VOLTAGE (V)
1964 G10
SHDN Pin Input Current
10
8 TJ = 25°C
POSITIVE CURRENT
6 FLOWS INTO THE PIN
4
2
0
–2
–4
–6
–8
–10
–10 –8 –6 –4 –2 0 2 4 6
SHDN PIN VOLTAGE (V)
8 10
1964 G13
Current Limit
–600
–500
∆VOUT = 100mV
–400
–300
–200
–100
0
0 –4 –8 –12 –16 –20
INPUT/OUTPUT DIFFERENTIAL (V)
1964 G16
GND Pin Current vs ILOAD
–4.0
VIN = VOUT(NOMINAL) – 1V
–3.5
–3.0 TJ = –50°C
–2.5
TJ = 25°C
–2.0
TJ = 125°C
–1.5
–1.0
–0.5
0
0 –40 –80 –120 –160 –200
OUTPUT CURRENT (mA)
1964 G11
SHDN Pin Input Current
12
VIN = –15V
9 POSITIVE CURRENT
FLOWS INTO THE PIN
6
VSHDN = 15V
3
0
VSHDN = –15V
–3
–6
–9
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1964 G14
Current Limit
–600
–500
VIN = –7V
VOUT = 0V
–400
–300
–200
–100
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1964 G17
SHDN Pin Thresholds
2.5
2.0
ON
1.5
1.0
0.5
0
OFF
–0.5
–1.0
–1.5
ON
–2.0
–2.5
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1964 G12
ADJ Pin Bias Current
–70
–60
–50
–40
–30
–20
–10
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1964 G15
Input Ripple Rejection
80
IL = –200mA
70 VIN = VOUT(NOMINAL) – 1V +
50mVRMS RIPPLE
60 CBYP = 0
50
40
COUT = 10µF
30
20
10
0
10
COUT = 1µF
100 1k 10k 100k
FREQUENCY (Hz)
1M
1964 G18
1964f
5
5 Page 
LT1964
APPLICATIO S I FOR ATIO
Calculating Junction Temperature
Example: Given an output voltage of –5V, an input voltage
range of –6V to –8V, an output current range of 0mA to
–100mA, and a maximum ambient temperature of 50°C,
what will the maximum junction temperature be?
The power dissipated by the device will be equal to:
IOUT(MAX) • (VIN(MAX) – VOUT) + (IGND • VIN(MAX))
where,
IOUT(MAX) = –100mA
VIN(MAX) = –8V
IGND at (IOUT = –100mA, VIN = –8V) = –2mA
so,
P = –100mA • (–8V + 5V) + (–2mA • –8V) = 0.32W
The thermal resistance (junction to ambient) will be in the
range of 125°C/W to 150°C/W depending on the copper
area. So the junction temperature rise above ambient will
be approximately equal to:
0.32W • 140°C/W = 44.2°C
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 + 44.2°C = 94.2°C
Protection Features
The LT1964 incorporates several protection features which
make it ideal for use in battery-powered circuits. In addi-
tion 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 output voltages.
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.
flow to less than 40µA. For adjustable versions, the output
will act like an open circuit, no current will flow into the pin.
If the input is powered by a voltage source, the output will
sink the short-circuit current of the device and will protect
itself by thermal limiting. In this case, grounding the SHDN
pin will turn off the device and stop the output from sinking
the short-circuit current.
Like many IC power regulators, the LT1964 series have
safe operating area protection. The safe area protection
activates at input-to-output differential voltages greater
than –7V. The safe area protection decreases the current
limit as the input-to-output differential voltage increases
and keeps the power transistor inside a safe operating
region for all values of forward input to-output voltage.
The protection is designed to provide some output current
at all values of input-to-output voltage up to the device
breakdown. A 50µA load is required at input-to-output
differential voltages greater than –7V.
When power is first turned on, as the input voltage rises,
the output follows the input, allowing the regulator to start
up into very heavy loads. During start-up, as the input
voltage is rising, the input-to-output voltage differential is
small, allowing the regulator to supply large output
currents. With a high input voltage, a problem can occur
wherein removal of an output short will not allow the
output voltage to fully recover. Other regulators, such as
the LT1175, also exhibit this phenomenon, so it is not
unique to the LT1964 series.
The problem occurs with a heavy output load when the
input voltage is high and the output voltage is low.
Common situations are immediately after the removal of
a short-circuit or when the SHDN pin is pulled high after
the input voltage has already been turned on. The load line
for such a load may intersect the output current curve at
two points. If this happens, there are two stable operating
points for the regulator. With this double intersection, the
input supply may need to be cycled down to zero and
brought up again to make the output recover.
The output of the LT1964 can be pulled above ground
without damaging the device. If the input is left open circuit
or grounded, the output can be pulled above ground by
20V. For fixed voltage versions, the output will act like a
large resistor, typically 500kΩ or higher, limiting current
1964f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
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| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet LT1964ES5-SD.PDF ] | |
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