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PDF LTC3533 Data sheet ( Hoja de datos )
| Número de pieza | LTC3533 | |
| Descripción | 2A Wide Input Voltage Synchronous Buck-Boost DC/DC Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
■ Regulated Output with Input Voltages Above,
Below or Equal to the Output
■ 1.8V to 5.5V (Input) and 5.25V (Output)
Voltage Range
■ 0.8A Continuous Output Current: VIN > 1.8V
■ 2A Continuous Output Current: VIN > 3V
■ Single Inductor
■ Synchronous Rectification: Up to 96% Efficiency
■ Programmable Burst Mode® Operation: IQ = 40µA
■ Output Disconnect in Shutdown
■ Programmable Frequency from 300kHz to 2MHz
■ <1µA Shutdown Current
■ Small Thermally Enhanced 14-Lead (3mm × 4mm ×
0.75mm) DFN package
APPLICATIONS
■ GSM Modems
■ Handheld Instruments
■ Digital Cameras
■ Smart Phones
■ Media Players
■ Miniature Hard Disk Drive Power
LTC3533
2A Wide Input Voltage
Synchronous Buck-Boost
DC/DC Converter
DESCRIPTION
The LTC®3533 is a wide VIN range, highly efficient, 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 product ideal for single cell lithium-ion/polymer
or multi-cell alkaline/NiMH applications where the output
voltage is within the input voltage range.
The LTC3533 features programmable Burst Mode opera-
tion, extended VIN and VOUT ranges down to 1.8V, and
increased output current. Switching frequencies up to
2MHz are programmed with an external resistor. The Burst
Mode threshold is programmed with a single resistor from
the BURST pin to GND.
Other features include 1µA shutdown current, short
circuit protection, programmable soft-start, current limit
and thermal shutdown. The LTC3533 is housed in the
thermally enhanced 14-lead (3mm × 4mm × 0.75mm)
DFN package.
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
2.2µH
VIN
2.4V TO 4.2V
OFF ON
10µF
SW1 SW2
PVIN
VIN
PVOUT
VOUT
LTC3533
RUN/SS
FB
RT VC
330pF
107k
4.7pF
340k 6.49k
47pF
VOUT
3.3V
1.5A
100µF
33.2k
SGND
BURST
PGND
200k
0.1µF
200k
3533 TA01
Efficiency
100
90
80 Burst Mode
OPERATION
70
60
50 VIN = 2.9V
VIN = 2.2V
40
VIN = 3.9V
30
20
10
0
0.1 1 10 100 1000 10000
OUTPUT CURRENT (mA)
3533 TA01b
3533f
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LTC3533
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise specified.
Switch Pins in Buck-Boost Mode
Switch Pins Entering Buck-Boost
Mode
Output Ripple at 1A Load
SW1
2V/DIV
SW2
2V/DIV
50ns/DIV
VIN = 3.3V
VOUT = 3.3V AT 500mA
SW1
2V/DIV
SW2
2V/DIV
3533 G10
50ns/DIV
VIN = 4.2V
VOUT = 3.3V AT 500mA
3533 G11
VIN = 2.7V
VIN = 3.3V
VIN = 4.2V
1µs/DIV
VOUT = 3.3V, 20mV/DIV
COUT = 100µF CERAMIC
3533 G12
Load Transient Response in Fixed
Frequency Mode, No Load to 1.5A
VOUT
100mV/DIV
IL
0.5A/DIV
100µs/DIV
VIN = 3.6V
VOUT = 3.3V
COUT = 100µF X5R CERAMIC
3533 G13
Load Transient Response in Auto
Burst Mode, No Load to 600mA
VOUT
100mV/DIV
LOAD
0.5A/DIV
100µs/DIV
VIN = 3.6V
VOUT = 3.3V
COUT = 100µF X5R CERAMIC +
100µF LOW ESR TANTALUM
3533 G14
Burst Mode Operation
Transition from Burst Mode
Operation to Fixed Frequency Mode
VOUT
50mV/DIV
INDUCTOR
CURRENT
0.5A/DIV
20µs/DIV
COUT = 100µF CERAMIC
3533 G15
VOUT
50mV/DIV
INDUCTOR
CURRENT
0.5A/DIV
200µs/DIV
COUT = 100µF CERAMIC
3533 G16
3533f
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LTC3533
APPLICATIONS INFORMATION
COMPONENT SELECTION
1 RT
2 BURST
3 SGND
4 SW1
5 PGND
6 PGND
7 SW2
VC 14
FB 13
RUN/SS 12
PVIN 11
VIN 10
PVOUT 9
VOUT 8
VIN
VOUT
GND MULTIPLE VIAS
3533 F04
Figure 4. Recommended Component Placement. Traces Carrying
High Current Should be Short and Wide. Trace Area at FB and VC
Pins are Kept Low. Lead Length to Battery Should be Kept Short.
PVOUT and PVIN Ceramic Capacitors Close to the IC Pins.
Inductor Selection
The high frequency operation of the LTC3533 allows the
use of small surface mount inductors. The inductor ripple
current is typically set to 20% to 40% of the maximum
inductor current. For a given ripple the inductance terms
are given as follows:
LBOOST
>
VIN(MIN)2
f•
• (VOUT − VIN(MIN))
∆IL • VOUT2
H
LBUCK
>
VOUT
f
• (VIN(MAX) − VOUT
• ∆IL • VIN(MAX)
)
H
where f = switching frequency, Hz
∆IL = maximum allowable inductor ripple current
VIN(MIN) = minimum input voltage
VIN(MAX) = maximum input voltage
VOUT = output voltage
For high efficiency, choose a ferrite inductor with a high
frequency core material to reduce core losses. The induc-
tor should have low ESR (equivalent series resistance) to
reduce the I2R losses, and must be able to handle the peak
inductor current without saturating. Molded chokes or chip
inductors usually do not have enough core to support the
peak inductor currents in the 4A to 6A region. To minimize
radiated noise, use a shielded inductor. See Table 1 for a
suggested list of inductor suppliers.
Output Capacitor Selection
The bulk value of the output filter capacitor is set to reduce
the ripple due to charge into the capacitor each cycle. The
steady state ripple due to charge is given by:
%Ripple
_
Boost
=
IOUT(MAX) •(VOUT − VIN(MIN))
COUT • VOUT2 • f
•
100
%
%Ripple
_
Buck
=
(VIN(MAX) − VOUT ) • 100
8L COUT • VIN(MAX) • f2
%
where COUT = output filter capacitor
IOUT(MAX) = maximum output load current
The output capacitance is usually many times larger than
the minimum value in order to handle the transient response
Table 1. Inductor Vendor Information
SUPPLIER
PHONE
Coilcraft
(847) 639-6400
CoEv Magnetics
(800) 227-7040
Murata
(814) 237-1431
(800) 831-9172
Sumida
USA: (847) 956-0666
Japan: 81(3) 3607-5111
TDK (847) 803-6100
TOKO
(847) 297-0070
FAX
(847) 639-1469
(650) 361-2508
(814) 238-0409
USA: (847) 956-0702
Japan: 81(3) 3607-5144
(847) 803-6296
(847) 699-7864
WEB SITE
www.coilcraft.com
www.circuitprotection.com/magnetics.asp
www.murata.com
www.sumida.com
www.component.tdk.com
www.tokoam.com
3533f
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11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC3533.PDF ] | |
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