|
|
PDF LT3973-3.3 Data sheet ( Hoja de datos )
| Número de pieza | LT3973-3.3 | |
| Descripción | Step-Down Regulator | |
| Fabricantes | Linear | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT3973-3.3 (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
|
No Preview Available !
FEATURES
nn Ultralow Quiescent Current
nn 2.5µA IQ at 12VIN to 3.3VOUT
nn Low Ripple Burst Mode® Operation
nn Output Ripple < 10mVP-P
nn Wide Input Voltage Range: 4.2V to 42V Operating
nn Adjustable Switching Frequency: 200kHz to 2.2MHz
nn Integrated Boost and Catch Diodes
nn 750mA Output Current
nn Excellent Start-Up and Dropout Performance
nn Fixed Output Voltages: 3.3V, 5V
nn 1.9µA IQ at 12VIN
nn Accurate Programmable Undervoltage Lockout
nn Low Shutdown Current: IQ = 0.75µA
nn Internal Catch Diode Current Limit
nn Power Good Flag
nn Thermal Shutdown
nn Small, Thermally Enhanced 10-Lead MSOP and
(3mm × 3mm) DFN Packages
APPLICATIONS
nn Automotive Battery Regulation
nn Power for Portable Products
nn Industrial Supplies
nn Gate Drive Bias
LT3973/LT3973-3.3/LT3973-5
42V, 750mA Step-Down
Regulator with 2.5µA
Quiescent Current and
Integrated Diodes
DESCRIPTION
The LT®3973 is an adjustable frequency monolithic buck
switching regulator that accepts a wide input voltage range
up to 42V, and consumes only 2.5µA of quiescent current.
A high efficiency switch is included on the die along with
the catch diode, boost diode, and the necessary oscillator,
control and logic circuitry. Low ripple Burst Mode operation
maintains high efficiency at low output currents while keep-
ing the output ripple below 10mV in a typical application.
A minimum dropout voltage of 530mV is maintained when
the input voltage drops below the programmed output volt-
age, such as during automotive cold crank. Current mode
topology is used for fast transient response and good loop
stability. A catch diode current limit provides protection
against shorted outputs and overvoltage conditions, with
thermal shutdown providing additional fault protection. An
accurate programmable undervoltage lockout feature is
available, producing a low shutdown current of 0.75µA.
A power good flag signals when VOUT reaches 90% of
the programmed output voltage. The LT3973 is available
in small, thermally enhanced 10-lead MSOP and 3mm ×
3mm DFN packages.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
TYPICAL APPLICATION
VIN
5.6V TO 42V
C1
4.7µF
5V Step-Down Converter
OFF ON
215k
VIN BOOST
LT3973
EN/UVLO SW
PG BD
OUT
RT FB
GND
C3
0.47µF
L1
15µH
15pF
1M
316k
VOUT
5V
750mA
C2
22µF
f = 600kHz
3973 TA01a
90 VIN = 12V
80
Efficiency
1000
100
70 10
60 1
50 0.1
40
0.01
0.1 1 10 100
LOAD CURRENT (mA)
0.01
3973 TA01b
For more information www.linear.com/LT3973
3973fb
1
1 page  
LT3973/LT3973-3.3/LT3973-5
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Efficiency, VOUT = 3.3V
90
VIN = 12V
80
70
VIN = 24V
VIN = 36V
60
50
40
FRONT PAGE APPLICATION
30
VOUT = 3.3V
R1 = 1M
20 R2 = 576k
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
LOAD CURRENT (A)
3973 G01
Efficiency, VOUT = 5V
90 VIN = 12V
80
70 VIN = 24V VIN = 36V
60
50
40
FRONT PAGE APPLICATION
30
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
LOAD CURRENT (A)
3973 G02
Efficiency, VOUT = 3.3V
90
80 VIN = 12V
70
60
VIN = 24V
VIN = 36V
50
40
30
20
0.01
FRONT PAGE APPLICATION
VOUT = 3.3V
R1 = 1M
R2 = 576k
0.1 1 10 100
LOAD CURRENT (mA)
3973 G03
Efficiency, VOUT = 5V
90
80 VIN = 12V
70
60
VIN = 24V
VIN = 36V
50
40
30
0.01
FRONT PAGE APPLICATION
0.1 1 10 100
LOAD CURRENT (mA)
3973 G04
LT3973 Feedback Voltage
1.220
1.215
1.210
1.205
1.200
1.195
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3973 G05
LT3973-3.3 Output Voltage
3.32
3.31
3.30
3.29
3.28
3.27
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3973 G06
LT3973-5 Output Voltage
5.04
5.02
5.00
4.98
4.96
4.94
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3973 G07
No-Load Supply Current
4.0 FRONT PAGE APPLICATION
VOUT = 3.3V
3.5
R1 = 1M
R2 = 576k
LT3973-3.3
3.0
2.5
2.0
1.5
5
10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3973 G08
For more information www.linear.com/LT3973
No-Load Supply Current
35
FRONT PAGE APPLICATION
30
VIN = 12V
VOUT = 3.3V
R1 = 1M
25 R2 = 576k
20
15
10
5
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
3973 G09
3973fb
5
5 Page 
LT3973/LT3973-3.3/LT3973-5
OPERATION
The LT3973 is a constant frequency, current mode step-
down regulator. An oscillator, with frequency set by RT,
sets an RS flip-flop, turning on the internal power switch.
An amplifier and comparator monitor the current flowing
between the VIN and SW pins, turning the switch-off when
this current reaches a level determined by the voltage at
VC (see Block Diagram). An error amplifier measures the
output voltage through an external resistor divider tied to
the FB pin and servos the VC node. If the error amplifier’s
output increases, more current is delivered to the output;
if it decreases, less current is delivered.
Another comparator monitors the current flowing through
the catch diode and reduces the operating frequency when
the current exceeds the 1.15A bottom current limit. This
foldback in frequency helps to control the output current
in fault conditions such as a shorted output with high
input voltage. Maximum deliverable current to the output
is therefore limited by both switch current limit and catch
diode current limit.
An internal regulator provides power to the control cir-
cuitry. The bias regulator normally draws power from
the VIN pin, but if the BD pin is connected to an external
voltage higher than 3.2V, bias power will be drawn from
the external source (typically the regulated output voltage).
This improves efficiency.
If the EN/UVLO pin is low, the LT3973 is shut down and draws
0.75µA from the input. When the EN/UVLO pin exceeds
1.19V, the switching regulator will become active. Under-
voltage lockout is programmable via this pin.
The switch driver operates from either VIN or from the
BOOST pin. An external capacitor is used to generate a
voltage at the BOOST pin that is higher than the input
supply. This allows the driver to fully saturate the internal
bipolar NPN power switch for efficient operation.
To further optimize efficiency, the LT3973 automatically
switches to Burst Mode operation in light load situations.
Between bursts, all circuitry associated with controlling
the output switch is shut down reducing the input supply
current to 1.8µA.
If the input voltage decreases towards the programmed
output voltage, the LT3973 will start to skip switch-off times
and decrease the switching frequency to maintain output
regulation up to a maximum duty cycle of approximately
97.5%. When the OUT pin is tied to VOUT, the LT3973
regulates the output such that it stays more than 530mV
below VIN; this sets a minimum dropout voltage. This
enforced minimum dropout voltage limits the duty cycle
and keeps the boost capacitor charged during dropout
conditions. Since sufficient boost voltage is maintained,
the internal switch can fully saturate yielding good dropout
performance.
The LT3973 contains a power good comparator which
trips when the FB pin is at 90% of its regulated value. The
PG output is an open-drain transistor that is off when the
output is in regulation, allowing an external resistor to pull
the PG pin high. Power good is valid when the LT3973 is
enabled and VIN is above 4.2V.
For more information www.linear.com/LT3973
3973fb
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT3973-3.3.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT3973-3.3 | Step-Down Regulator | Linear |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |