|
|
PDF LTC3499 Data sheet ( Hoja de datos )
| Número de pieza | LTC3499 | |
| Descripción | 750mA Synchronous Step-Up DC/DC Converters | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LTC3499 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
LTC3499/LTC3499B
750mA Synchronous
Step-Up DC/DC Converters
with Reverse-Battery Protection
FEATURES
■ Reverse-Battery Protection for DC/DC Converter
and Load
■ High Efficiency: Up to 94%
■ Generates 5V at 175mA from a 1.8V Input
■ Operates from 1.8V to 5.5V Input Supply
■ 2V to 6V Adjustable Output Voltage
www■.DaIntaruShseheCt4uUr.creonmt Controlled During Start-Up
■ Output Disconnnect in Shutdown
■ Low Noise 1.2MHz PWM Operation
■ Tiny External Components
■ Automatic Burst Mode® Operation (LTC3499)
■ Continuous Switching at Light Loads (LTC3499B)
■ Overvoltage Protection
■ 8-Lead (3mm × 3mm × 0.75mm) DFN
and MSOP Packages
U
APPLICATIO S
■ Medical Equipment
■ Digital Cameras
■ MP3 Players
■ Handheld Instruments
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
DESCRIPTIO
The LTC®3499/LTC3499B are synchronous, fixed fre-
quency step-up DC/DC power converters with integrated
reverse battery protection that protect and disconnect the
devices and load when the battery polarity is reversed while
delivering high efficiency in a small (3mm × 3mm) DFN
package. True output disconnect eliminates inrush current
and allows zero load current in shutdown.
The devices feature an input voltage range of 1.8V to 5.5V
enabling operation from two alkaline or NiMH batteries.
The switching frequency is internally set at 1.2MHz allow-
ing the use of tiny surface mount inductors and capacitors.
A minimal number of external components are required to
generate output voltages ranging from 2V to 6V. The
LTC3499 features automatic Burst Mode operation to
increase efficiency at light loads, while the LTC3499B
features continuous switching at light loads.
The soft-start time is externally programmable through a
small capacitor. Anti-ring circuitry reduces EMI emissions
by damping the inductor in discontinuous mode. The
devices feature <1µA shutdown supply current, integrated
overvoltage protection and are available in both 8-pin
(3mm × 3mm) DFN and 8-pin MSOP packages.
TYPICAL APPLICATIO
Two AA Cells to 5V Synchronous Boost Converter
VIN
1.8V TO 3.2V +
100k
330pF
4.7µH
2.2µF
VIN SW
LTC3499
ON OFF SHDN
VOUT
VC
FB
SS
GND
0.01µF
1M
324k
VOUT
5V
175mA
10µF
3499 TA01
Battery Current vs VIN
1.0
SHDN = 0V
VOUT = 0V
0.5
0
–0.5
–1.0
–6
–4 –2 0 2 4
VIN AND SW VOLTAGE (V)
6
3499 TA01b
3499f
1
1 page  
LTC3499/LTC3499B
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless noted.
FB Voltage vs Temperature
1.2225
1.2220
1.2215
1.2210
1.2205
1.2200
www.D1.a21t9a5Sheet4U.com
1.2190
1.2185
–50 –25
0
25 50 75 100
TEMPERATURE (°C)
3499 G09
Burst Mode Operation
(LTC3499 Only)
Oscillator Frequency
vs Temperature
1.4
1.3
1.2
1.1
1.0
–50 –25
0
25 50
TEMPERATURE (°C)
75 100
3499 G08
Load Transient 50mA to 200mA
VIN and SW Reverse-Battery
Current vs VIN and SW Voltage
1.0
SHDN = 0V
VOUT = 0V
0.5
0
–0.5
–1.0
–6
–4 –2 0 2 4
VIN AND SW VOLTAGE (V)
6
3499 G11
Fixed Frequency Discontinous
Mode Operation
VOUT
50mV/DIV
VOUT
200mV/DIV
IL
50mA/DIV
ILOAD 200mA
100mA/DIV
50mA
VIN = 2.4V
20µs/DIV
3499 G12
VOUT = 5V
L = 4.7µH
COUT = 10µF
CFF = 10pF (FEEDFORWARD CAPACITOR FROM
VOUT TO FB)
VIN = 2.4V
200µs/DIV
VOUT = 5V
ILOAD = 50mA to 200mA
RZ = 100k
CF = 680pF
COUT = 10µF
L = 4.7µH
SW
2V/DIV
IL
100mA/DIV
3499 G13
VIN = 2.4V
VOUT = 5V
L = 4.7µH
200ns/DIV
Soft-Start into 25Ω Load
VIN = 2.4V
VOUT = 5V
L = 4.7µH
CSS = 0.01µF
COUT = 10µF
1ms/DIV
VIN
2V/DIV
SS
2V/DIV
VOUT
2V/DIV
IL
200mA/DIV
34991G15
Fixed Frequency Operation
SW
2V/DIV
IL
100mA/DIV
VIN = 2.4V
VOUT = 5V
L = 4.7µH
200ns/DIV
3499 G16
3499 G14
3499f
5
5 Page 
LTC3499/LTC3499B
APPLICATIO S I FOR ATIO
Low ESR capacitors should be used to minimize output
voltage ripple. A 4.7µF to 10µF output capacitor is suffi-
cient for most applications and should be placed as close
to VOUT as possible. Larger values may be used to obtain
even lower output ripple and improve transient response.
X5R and X7R dielectric materials are preferred for their
ability to maintain capacitance over wide voltage and
temperature ranges.
Input Capacitor Selection
wwwT.DheatainSpheuet t4fiUlt.ecromcapacitor reduces peak currents drawn
from the input source and reduces input switching noise.
Ceramic capacitors are a good choice for input decoupling
due to their low ESR and ability to withstand reverse
voltage (i.e. non-polar nature). The capacitor should be
located as close as possible to the device. In most appli-
cations a 2.2µF input capacitor is sufficient. Larger values
may be used without limitations. Table 2 shows a list of
several ceramic capacitor manufacturers.
Table 2. Capacitor Vendor Information
SUPPLIER
WEB SITE
AVX www.avxcorp.com
Murata
www.murata.com
TDK www.component.tdk.com
Taiyo Yuden
www.t-yuden.com
Thermal Considerations
For the LTC3499/LTC3499B to deliver full output power, it
is imperative that a good thermal path be provided to
dissipate the heat generated within the package. For the
DFN package, this can be accomplished by taking advan-
tage of the large thermal pad on the underside of the
device. It is recommended that multiple vias in the printed
circuit board be used to conduct heat away from the part
and into a copper plane with as much area as possible. If
the junction temperature continues to rise, the part will go
into thermal shutdown where switching will stop until the
temperature drops.
Closing the Feedback Loop
The LTC3499/LTC3499B utilize current mode control,
with internal slope compensation. Current mode control
eliminates the 2nd order filter due to the inductor and
output capacitor exhibited in voltage mode controllers,
thus simplifying it to a single pole filter response. The
product of the modulator control to output DC gain and the
error amp open loop gain gives the DC gain of the system:
GDC
=
GCONTROL
•
GEA
•
VOUT
•
VREF
GCURRENT _ SENSE
GCONTROL
=
2
•
VIN
IOUT
,
( )GEA
~ 1000,
GCURRENT _ SENSE
=
1
RDS ON
The output filter pole is given by:
( )fFILTER_POLE =
IOUT
π • VOUT • COUT
where COUT is the output filter capacitor.
The output filter zero is given by:
( )fFILTER_ ZERO =
1
2 • π • RESR • COUT
where RESR is the capacitor equivalent series resistance.
A troublesome feature of the boost regulator topology is
the right half plane (RHP) zero, given by:
fRPHZ
=
(2
•
π
VIN2
• IOUT • VOUT
•L)
3499f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC3499.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LTC3490 | Single Cell 350mA LED Driver | Linear Technology |
| LTC3499 | 750mA Synchronous Step-Up DC/DC Converters | Linear Technology |
| LTC3499B | 750mA Synchronous Step-Up DC/DC Converters | 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 |