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PDF LTC3528-2 Data sheet ( Hoja de datos )
| Número de pieza | LTC3528-2 | |
| 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 Burst Mode® Operation with 12µA Quiescent Current
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 Noise Canceling Headphones
n Wireless Mice
n Bluetooth Headsets
LTC3528-2
1A, 2MHz Synchronous
Step-Up DC/DC Converter
in 2mm × 3mm DFN
DESCRIPTION
The LTC®3528-2 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 foot-
print by allowing the use of tiny, low profile inductors
and ceramic capacitors. The current mode PWM is inter-
nally compensated, simplifying the design process. The
LTC3528-2 enters Burst Mode operation at light loads.
Anti-ringing circuitry reduces EMI by damping the induc-
tor in discontinuous mode. Additional features include a
low shutdown current, open-drain power good output,
short-circuit protection and thermal overload protection.
The LTC3528-2 is offered in an 8-lead 2mm × 3mm ×
0.75mm DFN package.
L, LT, LTC, LTM, Burst Mode, 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
LTC3528-2
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
EFFICIENCY
70
1000
100
60 10
50
40 1
POWER LOSS
30
20 0.1
10
0 0.01
0.01 0.1 1 10 100 1000
LOAD CURRENT (mA)
35282 TA01b
35282fb
1
1 page  
LTC3528-2
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
Burst Mode Threshold Current
vs VIN
80 VOUT = 5V
60
EXIT BURST
40
ENTER BURST
20
0
1 1.5 2 2.5 3 3.5 4
VIN (V)
35242 G11
Oscillator Frequency Change
vs Temperature
2
1
0
–1
–2
–3
–4
–50 –25
0 25 50 75
TEMPERATURE (˚C)
100 125
35282 G14
Output Voltage vs Load Current
for VOUT = 5V
0.20 VIN = 3.6V
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
0
200 400
LOAD CURRENT (mA)
600
3528-2 G27
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
VOUT (V)
4 4.5 5
35282 G12
RDS(ON) Change vs Temperature
40
30
20
10
0
–10
–20
–50 –25
0 25 50 75
TEMPERATURE (˚C)
100 125
35282 G15
Output Voltage vs Load Current
for VOUT = 3.3V
0.20 VIN = 1.2V
0.15
0.10
0.05
0
–0.05
–0.10
–0.15
–0.20
0
50 100 150
LOAD CURRENT (mA)
200
35282 G28
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
VFB vs Temperature
1.200
1.199
1.198
1.197
1.196
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
35282 G16
Start-Up Voltage vs Temperature
850
800
750
700
650
600
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
35282 G17
35282fb
5
5 Page 
LTC3528-2
OPERATION (Refer to Block Diagram)
when switching between modes. In Burst Mode opera-
tion, energy is delivered to the output until it reaches the
nominal regulated value, then the LTC3528-2 transitions to
sleep mode where the outputs are off and the LTC3528–2
consumes only 12µA of quiescent current from VOUT. Once
the output voltage has drooped slightly, switching resumes
again. This maximizes efficiency at very light loads by
minimizing switching and quiescent current losses. Burst
Mode output ripple, which is typically 1% peak-to-peak,
can be reduced by using more output capacitance (10µF
or greater).
As the load current increases, the LTC3528-2 automati-
cally leaves Burst Mode operation. Note that larger output
capacitor values may cause this transition to occur at lighter
loads. The regulator will also leave Burst Mode operation if
a load transient occurs which causes the inductor current
to repeatedly reach current limit. Once the LTC3528-2 has
left Burst Mode operation and returned to normal opera-
tion, it will remain there until the output load is reduced
below the Burst threshold.
Burst Mode operation is inhibited during start-up and
until soft-start is done and VOUT is at least 0.24V greater
than VIN.
Single Cell to 5V Step-Up Applications
Due to the high inductor current slew rate in applications
boosting to 5V from a single cell (alkaline, NiCd or NiMH),
the LTC3528-2 may not enter Burst Mode operation at in-
put voltages below 1.5V. For single cell to 5V applications
requiring Burst Mode operation, the 1MHz LTC3528 is
recommended. Refer to the Typical Performance Charac-
teristics for the Burst Mode thresholds for different input
and output voltages.
35282fb
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LTC3528-2.PDF ] | |
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