|
|
PDF LT1933 Data sheet ( Hoja de datos )
| Número de pieza | LT1933 | |
| Descripción | 600mA 500kHz Step-Down Switching Regulator in SOT-23 | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT1933 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
FEATURES
■ Wide Input Range: 3.6V to 36V
■ 5V at 600mA from 16V to 36V Input
■ 3.3V at 600mA from 12V to 36V Input
■ 5V at 500mA from 6.3V to 36V Input
■ 3.3V at 500mA from 4.5V to 36V Input
■ Fixed Frequency 500kHz Operation
■ Uses Tiny Capacitors and Inductors
■ Soft-Start
■ Internally Compensated
■ Low Shutdown Current: <2µA
■ Output Adjustable Down to 1.25V
■ Low Profile (1mm) SOT-23 (ThinSOT™) Package
U
APPLICATIO S
■ Automotive Battery Regulation
■ Industrial Control Supplies
■ Wall Transformer Regulation
■ Distributed Supply Regulation
■ Battery-Powered Equipment
LT1933www.DataSheet4U.com
600mA, 500kHz Step-Down
Switching Regulator
in SOT-23
DESCRIPTIO
The LT®1933 is a current mode PWM step-down DC/DC
converter with an internal 0.75A power switch, packaged
in a tiny 6-lead SOT-23. The wide input range of 3.6V to
36V makes the LT1933 suitable for regulating power from
a wide variety of sources, including unregulated wall
transformers, 24V industrial supplies and automotive
batteries. Its high operating frequency allows the use of
tiny, low cost inductors and ceramic capacitors, resulting
in low, predictable output ripple.
Cycle-by-cycle current limit provides protection against
shorted outputs, and soft-start eliminates input current
surge during start up. The low current (<2µA) shutdown
provides output disconnect, enabling easy power man-
agement in battery-powered systems.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
4.5V TO 36V
OFF ON
3.3V Step-Down Converter
VIN BOOST
LT1933
SHDN
SW
GND FB
16.5k
1N4148
0.1µF
22µH
MBRM140
2.2µF
10k
VOUT
3.3V/500mA
22µF
1933 TA01a
Efficiency
95 VIN = 12V
90
85
80
VOUT = 5V
VOUT = 3.3V
75
70
65
0 100 200 300 400 500 600
LOAD CURRENT (mA)
1933 TA01b
1933f
1
1 page  
LT1933www.DataSheet4U.com
PI FU CTIO S
BOOST (Pin 1): The BOOST pin is used to provide a drive
voltage, higher than the input voltage, to the internal
bipolar NPN power switch.
GND (Pin 2): Tie the GND pin to a local ground plane below
the LT1933 and the circuit components. Return the feed-
back divider to this pin.
FB (Pin 3): The LT1933 regulates its feedback pin to
1.245V. Connect the feedback resistor divider tap to this
pin. Set the output voltage according to VOUT = 1.245V
(1 + R1/R2). A good value for R2 is 10k.
SHDN (Pin 4): The SHDN pin is used to put the LT1933 in
shutdown mode. Tie to ground to shut down the LT1933.
Tie to 2.3V or more for normal operation. If the shutdown
feature is not used, tie this pin to the VIN pin. SHDN also
provides a soft-start function; see the Applications Infor-
mation section.
VIN (Pin 5): The VIN pin supplies current to the LT1933’s
internal regulator and to the internal power switch. This
pin must be locally bypassed.
SW (Pin 6): The SW pin is the output of the internal power
switch. Connect this pin to the inductor, catch diode and
boost capacitor.
BLOCK DIAGRA
VIN
VIN 5
C2
INT REG
AND
UVLO
ON OFF
R3
SHDN
4
C4
SLOPE
COMP
Σ
OSC
FREQUENCY
FOLDBACK
VC
RQ
SQ
gm
1.245V
DRIVER
BOOST
1
Q1
SW
6
D2
C3
L1
D1
VOUT
C1
GND
2
FB
3
R2 R1
1933 BD
1933f
5
5 Page 
LT1933www.DataSheet4U.com
APPLICATIO S I FOR ATIO
At light loads, the inductor current becomes discontinu-
ous and the effective duty cycle can be very high. This
reduces the minimum input voltage to approximately
300mV above VOUT. At higher load currents, the inductor
current is continuous and the duty cycle is limited by the
maximum duty cycle of the LT1933, requiring a higher
input voltage to maintain regulation.
Soft-Start
The SHDN pin can be used to soft-start the LT1933,
reducing the maximum input current during start up. The
SHDN pin is driven through an external RC filter to create
a voltage ramp at this pin. Figure 4 shows the start up
waveforms with and without the soft-start circuit. By
choosing a large RC time constant, the peak start up
current can be reduced to the current that is required to
regulate the output, with no overshoot. Choose the value
of the resistor so that it can supply 60µA when the SHDN
pin reaches 2.3V.
Shorted and Reversed Input Protection
If the inductor is chosen so that it won’t saturate exces-
sively, an LT1933 buck regulator will tolerate a shorted
output. There is another situation to consider in systems
where the output will be held high when the input to the
LT1933 is absent. This may occur in battery charging
applications or in battery backup systems where a battery
or some other supply is diode OR-ed with the LT1933’s
output. If the VIN pin is allowed to float and the SHDN pin
is held high (either by a logic signal or because it is tied to
VIN), then the LT1933’s internal circuitry will pull its
quiescent current through its SW pin. This is fine if your
system can tolerate a few mA in this state. If you ground
the SHDN pin, the SW pin current will drop to essentially
zero. However, if the VIN pin is grounded while the output
is held high, then parasitic diodes inside the LT1933 can
RUN
5V/DIV
RUN SHDN
GND
1933 F04a
IIN
100mA/DIV
VOUT
5V/DIV
50µs/DIV
RUN
15k
0.1µF
RUN
5V/DIV
SHDN
GND
1933 F04b
IIN
100mA/DIV
VOUT
5V/DIV
0.5ms/DIV
Figure 4. To Soft-Start the LT1933, Add a Resistor and Capacitor to the SHDN Pin.
VIN = 12V, VOUT = 3.3V, COUT = 22µF, RLOAD = 10Ω.
1933f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LT1933.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT1930 | 1A/ 1.2MHz/2.2MHz/ Step-Up DC/DC Converters | Linear Technology |
| LT1930 | Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter | Linear Technology |
| LT1930A | 1A/ 1.2MHz/2.2MHz/ Step-Up DC/DC Converters | Linear Technology |
| LT1930A | Constant-Current/ Constant-Voltage 1.4MHz Step-Up DC/DC Converter | Linear Technology |
| 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 |