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PDF LT3091 Data sheet ( Hoja de datos )
| Número de pieza | LT3091 | |
| Descripción | 1.5A Negative Linear Regulator | |
| Fabricantes | Linear Technology Corporation | |
| Logotipo |  |
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LT3091
Features
–36V, 1.5A Negative
Linear Regulator with
Programmable Current Limit
Description
nn Output Current: 1.5A
nn Single Resistor Sets Output Voltage
nn 50µA SET Pin Current: ±1% Initial Accuracy
nn Programmable Current Limit
nn Positive or Negative Output Current Monitor
nn Parallelable for Higher Current and Heat Spreading
nn Low Dropout Voltage: 300mV
nn Low Output Noise: 18µVRMS (10Hz to 100kHz)
nn Configurable as a 3-Terminal Floating Regulator
nn Wide Input Voltage Range: –1.5V to –36V
nn Rail-to-Rail Output Voltage Range: 0V to –32V
nn Positive/Negative Shutdown Logic or UVLO
nn Programmable Cable Drop Compensation
nn Load Regulation: 1.2mV (1mA to 1.5A)
nn Stable with 10µF Minimum Output Capacitor
nn Stable with Ceramic or Tantalum Capacitors
nn Thermally Enhanced 14-Lead 4mm × 3mm DFN,
16-Lead TSSOP, 7-Lead TO-220 and DD Packages
Applications
nn Post Regulator for Switching Supplies
nn Low Noise Instrumentation and RF Supplies
nn Rugged Industrial Supplies
nn Precision Power Supplies
The LT®3091 is a 1.5A, low dropout negative linear
regulator that is easily paralleled to increase output
current or spread heat on surface mounted boards.
Designed with a precision current reference followed by a
high performance rail-to-rail voltage buffer, this regulator
finds use in applications requiring precision output, high
current with no heat sink, output adjustability to zero and
low dropout voltage. The device can also be configured
as a 3-terminal floating regulator.
The LT3091 features fast transient response, high PSRR
and output noise as low as 18µVRMS. The LT3091 generates
a wide output voltage range (0V to –32V) while maintain-
ing unity gain operation. This yields virtually constant
bandwidth, load regulation, PSRR and noise, independent
of the programmed output voltage.
The LT3091 supplies 1.5A at a typical dropout voltage of
300mV. Operating quiescent current is nominally 1.2mA
and drops to << 1µA in shutdown. A single resistor ad-
justs the LT3091’s precision programmable current limit.
The device’s positive or negative current monitor either
sources a current (0.25mA/A) or sinks a current (0.5mA/A)
proportional to output current. Built-in protection includes
reverse output protection, internal current limit with fold-
back and thermal shutdown with hysteresis.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Patent Pending.
Typical Application
0.1µF 49.9k
LT3091
SET
+
GND
TO ADC (IMON)
6.65k
IMONP OUT
10µF
VOUT
–2.5V
MAX IOUT
1.5A
VIN
–3V TO –10V
–
10µF
IN
50µA
SHDN
5k
ILIM
IMONN
3.3V
0.1µF
3091 TA01a
Output Noise: 10Hz to 100kHz
VOUT
100µV/DIV
1ms/DIV
VIN: –3.5V
COUT: 10µF, CSET: 0.1µF
VOUT: –2.5V
IL: 1.5A
3091 G39
For more information www.linear.com/LT3091
3091f
1
1 page  
LT3091
Electrical Characteristics
Note 1. Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2. The LT3091 is tested and specified under pulsed load conditions
such that TJ ≅ TA. The LT3091E is guaranteed to meet performance
specifications from 0°C to 125°C junction temperature. Specifications over
the –40°C to 125°C operating temperature range are assured by design,
characterization, and correlation with statistical process controls. The
LT3091I is guaranteed over the full –40°C to 125°C operating junction
temperature range. The LT3091MP is 100% tested and guaranteed
over the full –55°C to 150°C operating junction temperature range. The
LT3091H is 100% tested at the 150°C operating junction temperature.
High junction temperatures degrade operating lifetimes. Operating lifetime
is derated at junction temperatures greater than 125°C.
Note 3. Parasitic diodes exist internally between the OUT, SET, ILIM,
SHDN, IMONP, IMONN, and GND pins and the IN pin. Do not drive OUT,
SET, ILIM, SHDN, IMONP, IMONN, and GND pins more than 0.3V below
the IN pin during fault conditions. These pins must remain at a voltage
more positive than IN during normal operation.
Note 4. The LT3091 may go out of regulation if the minimum output
current requirement is not satisfied.
Note 5. Maximum junction temperature limits operating conditions. The
regulated output voltage specification does not apply for all possible
combinations of input voltage and output current, primarily due to the
internal current limit foldback which decreases current limit at VOUT –
VIN ≥ 7V. If operating at maximum output current, limit the input voltage
range. If operating at maximum input voltage, limit the output current
range.
Note 6. Load regulation is Kelvin sensed at the package.
Note 7. Dropout voltage is the minimum output-to-input voltage
differential needed to maintain regulation at a specified output current. In
dropout, the output voltage is: VIN + VDROPOUT.
Note 8. GND pin current is tested with VIN = VOUT(NOMINAL) and a current
source load. Therefore, the device is tested while operating in dropout.
This is the worst-case GND pin current. GND pin current decreases at
higher input voltages.
Note 9. The SET pin is clamped to OUT with diodes through 12k resistors.
These resistors and diodes only carry current under transient overloads or
fault conditions.
Note 10. Positive SHDN pin current flows into the SHDN pin.
Note 11. The SHDN threshold must be met to ensure device operation.
Note 12. Output noise decreases by adding a capacitor across the voltage
setting resistor. Adding this capacitor bypasses the voltage setting
resistor’s thermal noise as well as the reference current’s noise. Output
noise then equals the error amplifier noise (see Applications Information
section).
Note 13. The internal back-up current limit circuitry incorporates foldback
protection that decreases current limit for VOUT – VIN ≥ 7V. Some level of
output current is provided at all VOUT – VIN differential voltages. Please
consult the Typical Performance Characteristic graph for current limit vs
VOUT – VIN.
Note 14. The current limit programming scale factor is specified while
the internal backup current limit is not active. Please note that the internal
current limit has foldback protection for VOUT-to-VIN differentials greater
than 7V.
Note 15. For positive current monitoring, bias IMONN to ≥ 2V above
IMONP.
Typical Performance Characteristics TJ = 25°C, unless otherwise noted.
SET Pin Current
50.5
50.4
IL = 1mA
VOUT = –1.25V
50.3 VIN = –1.9V
50.2
50.1
50.0
49.9
49.8
49.7
49.6
49.5
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
3091 G01
SET Pin Current
N = 4726
49 49.5 50 50.5 51
DISTRIBUTION (µA)
3091 G02
Offset Voltage (VOUT – VSET)
2.0
IL = 1mA
1.5 VOUT = –1.25V
VIN = –1.9V
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
–75 –50 –25 0 25 50 75 100 125 150
TEMPERATURE (°C)
3091 G03
For more information www.linear.com/LT3091
3091f
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5 Page 
LT3091
Pin Functions (DFN/TSSOP/R/T7)
IN (Pins 1–4, Exposed Pad 15/Pins 1–4, Exposed Pad 17/
Pin 4, Tab/Pin 4, Tab): Input. These pins supply power to
the regulator. The exposed backside pad of the DFN and
TSSOP packages, as well as the tab of the DD-Pak and
TO-220 packages, is an electrical connection to IN and
the device’s substrate. For proper electrical and thermal
performance, tie all IN pins together and tie IN to the
exposed backside/tab of the package on the PCB. See the
Applications Information section for thermal considerations
and calculating junction temperature. The LT3091 requires
a bypass capacitor at IN. In general, a battery’s output
impedance rises with frequency, so include a bypass ca-
pacitor in battery powered applications. An input bypass
capacitor in the range of 4.7µF to 10µF generally suffices,
but applications with large load transients or longer input
lines may require higher input capacitance to prevent input
supply droop or input ringing.
ILIM (Pin 5/Pin 5/Pin 1/Pin 1): Current Limit Programming
Pin. Connecting an external resistor between the ILIM
and IN pins programs the current limit set point. For best
accuracy, Kelvin connect this resistor to the IN pins. The
programming scale factor is nominally 20A • kΩ. Current
limit is accurate to ±10% over temperature. If unused, tie
ILIM to IN and the internal current limit protects the part.
A parasitic substrate diode exists between the LT3091’s
ILIM and IN pins. Therefore, do not drive ILIM more than
0.3V below IN during normal operation or during a fault
condition.
IMONP (Pin 6/Pin 6/NA/NA): Positive Current Monitoring
Pin. For positive current monitoring, connect a resistor
between IMONP and GND. IMONP sources current equal to
1/4000 of output current. For negative current monitoring,
tie this pin to IN. For proper operation, IN and IMONP must
be at least 2V below IMONN. If unused, tie IMONP to IN.
A parasitic substrate diode exists between the LT3091’s
IMONP and IN pins. Therefore, do not drive IMONP more
than 0.3V below IN during normal operation or during a
fault condition.
IMONN (Pin7/Pin7/Pin2/Pin2):NegativeCurrentMonitor-
ing Pin. For negative current monitoring, connect a resistor
between IMONN and GND. IMONN sinks current equal to
1/2000 of output current. For positive current monitor-
ing, bias IMONN to a positive supply voltage (at least 2V
above IMONP). If unused, tie IMONN to the GND pin. A
parasitic substrate diode exists between the LT3091’s
IMONN and IN pins. Therefore, do not drive IMONN more
than 0.3V below IN during normal operation or during a
fault condition.
SHDN (Pin 8/Pin 10/Pin 3/Pin 3): Shutdown. Use the SHDN
pin to put the LT3091 into a micropower shutdown state
and to turn off the output voltage. The SHDN function is
bidirectional, allowing either positive or negative logic to
turn the regulator ON/OFF. The SHDN pin threshold volt-
ages are referenced to GND. The output of the LT3091 is
OFF if the SHDN pin is pulled within ±0.45V of GND. Driv-
ing the SHDN pin more than ±1.4V turns the LT3091 ON.
Drive the SHDN pin with either a logic gate or with open
collector/drain logic using a pull-up resistor. The resistor
supplies the pull-up current of the open collector/drain
gate. The maximum SHDN pin current is 7µA out of the
pin (for negative logic) or 30µA into the pin (for positive
logic). If the SHDN function is unused, connect the SHDN
pin to VIN or a positive bias voltage to turn the device ON.
Do not float the SHDN pin. As detailed in the Applications
Information section, the SHDN pin can also be used to set
a programmable undervoltage lockout (UVLO) threshold. A
parasitic diode exists between the LT3091’s SHDN and IN
pins. Therefore, do not drive SHDN more than 0.3V below
IN during normal operation or during a fault condition.
SET (Pin 9/Pin 11/Pin 5/Pin 5): SET. This pin is the invert-
ing input to the error amplifier and the regulation setpoint
for the device. A precision fixed current of 50µA flows into
this pin. Connecting a resistor from SET to GND programs
the LT3091’s output voltage. Output voltage range is from
zero to –32V. Adding a bypass capacitor from SET to GND
improves transient response, PSRR, noise performance
and soft starts the output. Kelvin connect the GND side of
the SET pin resistor to the load for optimum load regulation
performance. A parasitic substrate diode exists between
the LT3091’s SET and IN pins. Therefore, do not drive
SET more than 0.3V below IN during normal operation
or during a fault condition.
For more information www.linear.com/LT3091
3091f
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LT3091.PDF ] | |
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