|
|
PDF LTC3440 Data sheet ( Hoja de datos )
| Número de pieza | LTC3440 | |
| Descripción | Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LTC3440 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
www.DataSheet4U.com
FEATURES
s Single Inductor
s Fixed Frequency Operation with Battery Voltages
Above, Below or Equal to the Output
s Synchronous Rectification: Up to 96% Efficiency
s 25µA Quiescent Current in Burst Mode® Operation
s Up to 600mA Continuous Output Current
s No Schottky Diodes Required (VOUT < 4.3V)
s VOUT Disconnected from VIN During Shutdown
s 2.5V to 5.5V Input and Output Range
s Programmable Oscillator Frequency
from 300kHz to 2MHz
s Synchronizable Oscillator
s Burst Mode Enable Control
s <1µA Shutdown Current
s Small Thermally Enhanced 10-Pin MSOP Package
U
APPLICATIO S
s Palmtop Computers
s Handheld Instruments
s MP3 Players
s Digital Cameras
LTC3440
Micropower Synchronous
Buck-Boost DC/DC Converter
DESCRIPTIO
The LTC®3440 is a high efficiency, fixed frequency, Buck-
Boost DC/DC converter that operates from input voltages
above, below or equal to the output voltage. The topology
incorporated in the IC provides a continuous transfer
function through all operating modes*, making the prod-
uct ideal for single lithium-ion, multicell alkaline or NiMH
applications where the output voltage is within the battery
voltage range.
The device includes two 0.19Ω N-channel MOSFET
switches and two 0.22Ω P-channel switches. Switching
frequencies up to 2MHz are programmed with an external
resistor and the oscillator can be synchronized to an
external clock. Quiescent current is only 25µA in Burst
Mode operation, maximizing battery life in portable appli-
cations. Burst Mode operation is user controlled and can
be enabled by driving the MODE/SYNC pin high. If the
MODE/SYNC pin has either a clock or is driven low, then
fixed frequency switching is enabled.
Other features include a 1µA shutdown, soft-start con-
trol, thermal shutdown and current limit. The LTC3440 is
available in the 10-pin thermally enhanced MSOP
package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
*Patent Pending
TYPICAL APPLICATIO
Li-Ion to 3.3V at 600mA Buck-Boost Converter
L1
10µH
VIN = 2.7V TO 4.2V
3
SW1
4
SW2
7 LTC3440
6
VIN VOUT
+
Li-Ion
8
SHDN/SS
FB
2
C1 *
MODE/SYNC VC
10µF 1
RT
GND
RT
60.4k
9
C5 1.5nF
10
R3
5 15k
R1
340k
R2
200k
VOUT
3.3V
600mA
C2
22µF
*1 = Burst Mode OPERATION
0 = FIXED FREQUENCY
C1: TAIYO YUDEN JMK212BJ106MG
C2: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CDRH6D38-100
3440 TA01
Efficiency vs VIN
100
VOUT = 3.3V
98 IOUT = 100mA
96 FOSC = 1MHz
94
92
90
88
86
84
82
80
2.5 3.0 3.5 4.0 4.5 5.0 5.5
VIN (V)
3440 TA02
3440f
1
1 page  
www.DataSheet4U.com
TYPICAL PERFOR A CE CHARACTERISTICS
Boost Max Duty Cycle
90
VIN = VOUT = 3.6V
RT = 60k
Minimum Start Voltage
2.40
85
2.35
80
2.30
75
LTC3440
Current Limit
3000
2500
PEAK SWITCH
VIN = VOUT = 3.6V
2000
1500
AVERAGE INPUT
70
–55 –25
5
35 65
TEMPERATURE (°C)
95 125
3440 G19
2.25
–55
–25 5 35 65
TEMPERATURE (°C)
95 125
3440 G20
1000
–55 –25
5
35 65
TEMPERATURE (°C)
95 125
3440 G21
PI FU CTIO S
RT (Pin 1): Timing Resistor to Program the Oscillator
Frequency. The programming frequency range is 300kHz
to 2MHz.
fOSC
=
6
• 1010
RT
Hz
MODE/SYNC (Pin 2): MODE/SYNC = External CLK : Syn-
chronization of the internal oscillator. A clock frequency of
twice the desired switching frequency and with a pulse
width between 100ns and 2µs is applied. The oscillator
free running frequency is set slower than the desired
synchronized switching frequency to guarantee sync. The
oscillator RT component value required is given by:
RT
=
8 •1010
fSW
where fSW = desired synchronized switching frequency.
SW1 (Pin 3) : Switch Pin Where the Internal Switches A
and B are Connected. Connect inductor from SW1 to SW2.
An optional Schottky diode can be connected from SW1 to
ground. Minimize trace length to keep EMI down.
SW2 (Pin 4): Switch Pin Where the Internal Switches C
and D are Connected. For applications with output volt-
ages over 4.3V, a Schottky diode is required from SW2 to
VOUT to ensure the SW pin does not exhibit excess voltage.
GND (Pin 5): Signal and Power Ground for the IC.
VOUT (Pin 6): Output of the Synchronous Rectifier. A filter
capacitor is placed from VOUT to GND.
VIN (Pin 7): Input Supply Pin. Internal VCC for the IC. A
ceramic bypass capacitor as close to the VIN pin and GND
(Pin 5) is required.
SHDN/SS (Pin 8): Combined Soft-Start and Shutdown.
Grounding this pin shuts down the IC. Tie to >1.5V to
enable the IC and > 2.5V to ensure the error amp is not
clamped from soft-start. An RC from the shutdown com-
mand signal to this pin will provide a soft-start function by
limiting the rise time of the VC pin.
FB (Pin 9): Feedback Pin. Connect resistor divider tap
here. The output voltage can be adjusted from 2.5V to
5.5V. The feedback reference voltage is typically 1.22V.
VC (Pin 10): Error Amp Output. A frequency compensation
network is connected from this pin to the FB pin to
compensate the loop. See the section “Compensating the
Feedback Loop” for guidelines.
3440f
5
5 Page 
www.DataSheet4U.com
LTC3440
APPLICATIO S I FOR ATIO
Input Capacitor Selection
Since the VIN pin is the supply voltage for the IC it is
recommended to place at least a 4.7µF, low ESR bypass
capacitor.
Table 2. Capacitor Vendor Information
SUPPLIER PHONE
FAX
AVX (803) 448-9411 (803) 448-1943
Sanyo
(619) 661-6322 (619) 661-1055
Taiyo Yuden (408) 573-4150 (408) 573-4159
WEB SITE
www.avxcorp.com
www.sanyovideo.com
www.t-yuden.com
Optional Schottky Diodes
To achieve a 1%-2% efficiency improvement above 50mW,
Schottky diodes can be added across synchronous switches
B (SW1 to GND) and D (SW2 to VOUT). The Schottky
diodes will provide a lower voltage drop during the break-
before-make time (typically 15ns) of the NMOS to PMOS
transition. General purpose diodes such as a 1N914 are
not recommended due to the slow recovery times and will
compromise efficiency. If desired a large Schottky diode,
such as an MBRM120T3, can be used from SW2 to VOUT.
A small diode, such as ZHCS400 from Zetex or CMDSH2-3
from Central Semiconductor, can be used from SW1 to
GND.
Output Voltage > 4.3V
A Schottky diode from SW to VOUT is required for output
voltages over 4.3V. The diode must be located as close to
the pins as possible in order to reduce the peak voltage on
SW2 due to the parasitic lead and trace inductance.
Input Voltage > 4.5V
For applications with input voltages above 4.5V which
could exhibit an overload or short-circuit condition, a 2Ω/
1nF series snubber is required between the SW1 pin and
GND. A Schottky diode from SW1 to VIN should also be
added as close to the pins as possible. For the higher input
voltages VIN bypassing becomes more critical, therefore,
a ceramic bypass capacitor as close to the VIN and GND
pins as possible is also required.
Operating Frequency Selection
There are several considerations in selecting the operating
frequency of the converter. The first is, what are the
sensitive frequency bands that cannot tolerate any spec-
tral noise? For example, in products incorporating RF
communications, the 455kHz IF frequency is sensitive to
any noise, therefore switching above 600kHz is desired.
Some communications have sensitivity to 1.1MHz and in
that case a 2MHz converter frequency may be employed.
Other considerations are the physical size of the converter
and efficiency. As the operating frequency goes up, the
inductor and filter capacitors go down in value and size.
The trade off is in efficiency since the switching losses due
to gate charge are going up proportional with frequency.
Additional quiescent current due to the output switches
GATE charge is given by:
Buck: 500e–12 • VIN • F
Boost: 250e–12 • (VIN + VOUT) • F
Buck/Boost: F • (750e–12 • VIN + 250e–12 • VOUT)
where F = switching frequency
Closing the Feedback Loop
The LTC3440 incorporates voltage mode PWM control.
The control to output gain varies with operation region
(Buck, Boost, Buck-Boost), but is usually no greater than
15. The output filter exhibits a double pole response is
given by:
fFILTER_POLE = 2 • π •
1 Hz
L • COUT
where COUT is the output filter capacitor.
The output filter zero is given by:
fFILTER_ ZERO
=
2
•
π
•
1
RESR
•
COUT
Hz
where RESR is the capacitor equivalent series resistance.
3440f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC3440.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LTC3440 | Dual DC/DC Converter with USB Power Manager and Li-Ion Battery Charger | Linear Technology |
| LTC3441 | High Current Micropower Synchronous Buck-Boost DC/DC Converter | Linear Technology |
| LTC3442 | Micropower Synchronous Buck-Boost DC/DC Converter | Linear Technology |
| LTC3443 | High Current Micropower 600kHz Synchronous Buck-Boost 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 |