|
|
PDF LTC3405A-1.5 Data sheet ( Hoja de datos )
| Número de pieza | LTC3405A-1.5 | |
| Descripción | 1.5V / 1.8V / 1.5MHz - 300mA Synchronous Step-Down Regulators in ThinSOT | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LTC3405A-1.5 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
|
No Preview Available !
FEATURES
s High Efficiency: Up to 93%
s Very Low Quiescent Current: Only 20µA
During Operation
s 300mA Output Current at VIN = 3V
s 2.5V to 5.5V Input Voltage Range
s 1.5MHz Constant Frequency Operation
s No Schottky Diode Required
s Low Dropout Operation: 100% Duty Cycle
s Stable with Ceramic Capacitors
s Shutdown Mode Draws < 1µA Supply Current
s ±3% Output Voltage Accuracy
s Current Mode Operation for Excellent Line and
Load Transient Response
s Overtemperature Protected
s Low Profile (1mm) ThinSOTTM Package
U
APPLICATIO S
s Cellular Telephones
s Personal Information Appliances
s Wireless and DSL Modems
s Digital Still Cameras
s MP3 Players
s Portable Instruments
LTC3405A-1.5/LTwCww.3Da4ta0She5eAt4U.-c1om.8
1.5V, 1.8V, 1.5MHz, 300mA
Synchronous Step-Down
Regulators in ThinSOT
DESCRIPTIO
The LTC®3405A-1.5/LTC3405A-1.8 are high efficiency
monolithic synchronous buck regulators using a constant
frequency, current mode architecture. Supply current
during operation is only 20µA and drops to <1µA in
shutdown. The 2.5V to 5.5V input voltage range makes the
LTC3405A-1.5/LTC3405A-1.8 ideally suited for single
Li-Ion battery-powered applications. 100% duty cycle
provides low dropout operation, extending battery life in
portable systems.
Switching frequency is internally set at 1.5MHz, allowing
the use of small surface mount inductors and capacitors.
The LTC3405A-1.5/LTC3405A-1.8 are specifically designed
to work well with ceramic output capacitors, achieving
very low output voltage ripple and a small PCB footprint.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. The
LTC3405A-1.5/LTC3405A-1.8 are available in a low profile
(1mm) ThinSOT package.
For adjustable output voltage, refer to the LTC3405A data
sheet.
, LTC and LT are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
VIN
2.7V
TO 5.5V
CIN**
4.7µF
CER
4
VIN
3 4.7µH*
SW
LTC3405A-1.8
1
RUN
65
MODE VOUT
GND
2
3405A1518 F01
*MURATA LQH3C4R7M34
**TAIYO YUDEN JMK212BJ475MG
VOUT
1.8V
300mA
COUT**
4.7µF
CER
Figure 1a. High Efficiency Step-Down Converter
100
VIN = 2.7V
90
80 VIN = 3.6V
VIN = 4.2V
70
VIN = 5.5V
60
50
40
0.1
1 10 100
OUTPUT CURRENT (mA)
1000
3405A1518 F01b
Figure 1b. Efficiency vs Load Current
sn3405a1518 3405a1518fs
1
1 page  
LTC3405A-1.5/LTwCww.3Da4ta0She5eAt4U.-c1om.8
TYPICAL PERFOR A CE CHARACTERISTICS
(From Figure 1a)
Load Step
VOUT
100mV/DIV
AC
COUPLED
IL
200mA/DIV
Load Step
VOUT
100mV/DIV
AC
COUPLED
IL
200mA/DIV
Load Step
VOUT
100mV/DIV
AC
COUPLED
IL
200mA/DIV
ILOAD
200mA/DIV
ILOAD
200mA/DIV
ILOAD
200mA/DIV
VIN = 3.6V
40µs/DIV
VOUT = 1.8V
ILOAD = 20mA TO 250mA
PULSE SKIPPING MODE
3405A1518 G20
VIN = 3.6V
40µs/DIV
VOUT = 1.8V
ILOAD = 20mA TO 250mA
Burst Mode OPERATION
3405A1518 G21
VIN = 3.6V
40µs/DIV
VOUT = 1.8V
ILOAD = 0mA TO 250mA
Burst Mode OPERATION
3405A1518 G22
PI FU CTIO S
RUN (Pin 1): Run Control Input. Forcing this pin above
1.5V enables the part. Forcing this pin below 0.3V shuts
down the device. In shutdown, all functions are disabled
drawing <1µA supply current. Do not leave RUN floating.
GND (Pin 2): Ground Pin.
SW (Pin 3): Switch Node Connection to Inductor. This pin
connects to the drains of the internal main and synchro-
nous power MOSFET switches.
VIN (Pin 4): Main Supply Pin. Must be closely decoupled
to GND, Pin 2, with a 2.2µF or greater ceramic capacitor.
VOUT (Pin 5): Output Voltage Feedback Pin. An internal
resistive divider divides the output voltage down for com-
parison to the internal 1.2V reference voltage.
MODE (Pin 6): Mode Select Input. To select pulse skip-
ping mode, tie to VIN. Grounding this pin selects Burst
Mode operation. Do not leave this pin floating.
sn3405a1518 3405a1518fs
5
5 Page 
LTC3405A-1.5/LTwCww.3Da4ta0She5eAt4U.-c1om.8
APPLICATIO S I FOR ATIO
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3405A series parts. These items are also illustrated
graphically in Figures 4 and 5. Check the following in your
layout:
1. The power traces, consisting of the GND trace, the SW
trace and the VIN trace should be kept short, direct and
wide.
2. Does the (+) plate of CIN connect to VIN as closely as
possible? This capacitor provides the AC current to the
internal power MOSFETs.
3. Keep the (–) plates of CIN and COUT as close as possible.
Design Example
As a design example, assume the LTC3405A-1.8 is used
in a single lithium-ion battery-powered cellular phone
application. The VIN will be operating from a maximum of
4.2V down to about 2.7V. The load current requirement
is a maximum of 0.25A but most of the time it will be in
standby mode, requiring only 2mA. Efficiency at both low
and high load currents is important. Output voltage is
1.8V. With this information we can calculate L using
equation (1),
L
=
1
(f)(∆IL )
VOUT 1−
VOUT
VIN
(3)
Substituting VOUT = 1.8V, VIN = 4.2V, ∆IL = 100mA and
f = 1.5MHz in equation (3) gives:
L
=
1.8V
1.5MHz(100mA)
1−
1.8V
4.2V
≅
6.8µH
For best efficiency choose a 300mA or greater inductor
with less than 0.3Ω series resistance.
CIN will require an RMS current rating of at least 0.125A ≅
ILOAD(MAX)/2 at temperature and COUT will require an ESR
of less than 0.5Ω. In most cases, a tantalum capacitor will
satisfy this requirement.
Figure 6 shows the complete circuit along with its effi-
ciency curve.
16
RUN MODE
–
VOUT
+
COUT
L1
LTC3405A-1.8
25
GND VOUT
3 SW
4
VIN
CIN
VIN
3405A1518 F04
BOLD LINES INDICATE HIGH CURRENT PATHS
Figure 4. LTC3405A-1.8 Layout Diagram
VOUT
PIN 1
L1 SW
VIA TO VIN
LTC3405A-1.8
VIN
COUT
GND
CIN
3405A1518 F05
Figure 5. LTC3405A-1.8 Suggested Layout
sn3405a1518 3405a1518fs
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC3405A-1.5.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LTC3405A-1.375 | 1.375V / 1.5MHz - 300mA Synchronous Step-Down Regulators in ThinSOT | Linear Technology |
| LTC3405A-1.5 | 1.5V / 1.8V / 1.5MHz - 300mA Synchronous Step-Down Regulators in ThinSOT | Linear Technology |
| LTC3405A-1.8 | 1.5V / 1.8V / 1.5MHz - 300mA Synchronous Step-Down Regulators in ThinSOT | 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 |