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PDF LTC3528B-2 Data sheet ( Hoja de datos )
| Número de pieza | LTC3528B-2 | |
| Descripción | 2MHz Synchronous Step-Up DC/DC Converter | |
| Fabricantes | Linear | |
| Logotipo |  |
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FEATURES
n Delivers 3.3V at 200mA from a Single Alkaline/
NiMH Cell or 3.3V at 400mA from Two Cells
n VIN Start-Up Voltage: 700mV
n 0.50V to 5.5V Input Range
n 1.6V to 5.25V VOUT Range
n Up to 94% Efficiency
n Output Disconnect
n 2MHz Fixed Frequency Operation
n VIN > VOUT Operation
n Integrated Soft-Start
n Current Mode Control with Internal Compensation
n Low Noise PWM Operation
n Internal Synchronous Rectifier
n Logic Controlled Shutdown: <1µA
n Anti-Ringing Control
n Low Profile (2mm × 3mm × 0.75mm) DFN Package
APPLICATIONS
n Medical Instruments
n Flash-Based MP3 Players
n Noise Canceling Headphones
n Wireless Mice
n Bluetooth Headsets
LTC3528B-2
1A, 2MHz Synchronous
Step-Up DC/DC Converter
in 2mm × 3mm DFN
DESCRIPTION
The LTC®3528B-2 is a synchronous, fixed frequency
step-up DC/DC converter with output disconnect. High
efficiency synchronous rectification, in addition to a 700mV
start-up voltage and operation down to 500mV once
started, provides longer run-time for single or multiple
cell battery-powered products.
A switching frequency of 2MHz minimizes solution
footprint by allowing the use of tiny, low profile induc-
tors and ceramic capacitors. The current mode PWM is
internally compensated, simplifying the design process.
The LTC3528B-2 features continuous switching at light
loads. Anti-ringing circuitry reduces EMI by damping the
inductor in discontinuous mode. Additional features include
a low shutdown current, open-drain power good output,
short-circuit protection and thermal overload protection.
The LTC3528B-2 is offered in an 8-lead 2mm × 3mm ×
0.75mm DFN package.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
TYPICAL APPLICATION
2.2µH
VIN
1.8V TO 3.2V
4.7µF
OFF ON
SW
VIN VOUT
LTC3528B-2
PGOOD
SHDN
GND
FB
499k
287k
68pF
VOUT
3.3V
400mA
10µF
35282 TA01a
Efficiency and Power Loss
100
90
VOUT = 3.3V
VIN = 2.4V
80
1000
70
60 EFFICIENCY
100
50
40 POWER LOSS
30 10
20
10
01
0.1 1 10 100 1000
LOAD CURRENT (mA)
35282 TA01b
3528b2fa
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1 page  
LTC3528B-2
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
Oscillator Frequency Change
vs VOUT
0.50
0.25
0
–0.25
–0.50
–0.75
–1.00
–1.25
–1.50
–1.75
–2.00
–2.25
1.5 2 2.5 3 3.5 4 4.5 5
VOUT (V)
35282 G12
RDS(ON) vs VOUT
450
400
350
300
PMOS
250
200
NMOS
150
100
1.5 2 2.5 3 3.5 4 4.5 5
VOUT (V)
35282 G13
Oscillator Frequency Change
vs Temperature
2
1
0
–1
–2
–3
–4
–50 –25
0 25 50 75
TEMPERATURE (˚C)
100 125
35282 G14
RDS(ON) Change vs Temperature
40
VFB vs Temperature
1.200
Start-Up Voltage vs Temperature
850
30
1.199
20
10 1.198
0
1.197
–10
800
750
700
650
–20
–50 –25
0 25 50 75 100 125
TEMPERATURE (˚C)
1.196
–50 –25
35282 G15
Fixed Frequency
Inductor Current
WVOaUvTefRoirpmpsle
and
0 25 50 75
TEMPERATURE (°C)
100 125
35282 G16
600
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
35282 G17
VOUT and IIN During Soft-Start
VOUT
20mV/DIV
IL
200mA/DIV
VIN = 1.2V
VOUT = 3.3V
COUT = 10µF
CFF = 33pF
IOUT = 100mA
L = 2.2µH
500ns/DIV
35282 G19
VOUT
1V/DIV
IIN
200mA/DIV
SHDN PIN
VIN = 1.2V
VOUT = 3.3V
COUT = 10µF
L = 2.2µH
200µs/DIV
35282 G21
3528b2fa
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5 Page 
LTC3528B-2
APPLICATIONS INFORMATION
The inductor current ripple is typically set for 20% to
40% of the maximum inductor current. High frequency
ferrite core inductor materials reduce frequency dependent
power losses compared to cheaper powdered iron types,
improving efficiency. The inductor should have low ESR
(series resistance of the windings) to reduce the I2R power
losses, and must be able to handle the peak inductor current
without saturating. Molded chokes and some chip induc-
tors usually do not have enough core area to support the
peak inductor currents of 1.5A seen on the LTC3528B-2.
To minimize radiated noise, use a shielded inductor. See
Table 1 for suggested components and suppliers.
Table 1. Recommended Inductors
VENDOR
PART/STYLE
Coilcraft
(847) 639-6400
www.coilcraft.com
DO1606T, MSS5131, MSS5121
MSS6122, MOS6020
ME3220, DO1608C
1812PS
Coiltronics
SD12, SD14, SD20
SD25, SD52
Sumida
(847) 956-0666
www.sumida.com
CD43
CDC5D23B
CDRH5D18
TDK VLP, VLF
VLCF, SLF, VLS
Toko
(408) 432-8282
www.tokoam.com
D53, D62, D63
D73, D75
Wurth
(201) 785-8800
www.we-online.com
WE-TPC type M, MH
Output and Input Capacitor Selection
Low ESR (equivalent series resistance) capacitors should
be used to minimize the output voltage ripple. Multilayer
ceramic capacitors are an excellent choice as they have
extremely low ESR and are available in small footprints.
A 10µF to 22µF output capacitor is sufficient for most ap-
plications. Values larger than 22µF may be used to obtain
extremely low output voltage ripple and improve transient
response. X5R and X7R dielectric materials are preferred
for their ability to maintain capacitance over wide voltage
and temperature ranges. Y5V types should not be used.
The internal loop compensation of the LTC3528B-2 is
designed to be stable with output capacitor values of 10µF
or greater. Although ceramic capacitors are recommended,
low ESR tantalum capacitors may be used as well.
A small ceramic capacitor in parallel with a larger tantalum
capacitor may be used in demanding applications which
have large load transients. Another method of improving the
transient response is to add a small feed-forward capaci-
tor across the top resistor of the feedback divider (from
VOUT to FB). A typical value of 33pF will generally suffice.
Low ESR input capacitors reduce input switching noise
and reduce the peak current drawn from the battery. It
follows that ceramic capacitors are also a good choice
for input decoupling and should be located as close as
possible to the device. A 10µF input capacitor is sufficient
for most applications. Larger values may be used without
limitations. Table 2 shows a list of several ceramic capaci-
tor manufacturers. Consult the manufacturers directly for
detailed information on their selection of ceramic parts.
Table 2. Capacitor Vendor Information
SUPPLIER
PHONE
WEBSITE
AVX (803) 448-9411 www.avxcorp.com
Murata
(714) 852-2001 www.murata.com
Taiyo-Yuden
(408) 573-4150 www.t-yuden.com
TDK (847) 803-6100 www.component.tdk.com
3528b2fa
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| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LTC3528B-2.PDF ] | |
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