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PDF LTC3124HFE Data sheet ( Hoja de datos )
| Número de pieza | LTC3124HFE | |
| Descripción | 5A 2-Phase Synchronous Step-Up DC/DC Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3124
15V, 5A 2-Phase Synchronous
Step-Up DC/DC Converter with
Output Disconnect
FEATURES
n VIN Range: 1.8V to 5.5V, 500mV After Start-Up
n Adjustable Output Voltage: 2.5V to 15V
n 1.5A Output Current for VIN = 5V and VOUT = 12V
n Dual-Phase Control Reduces Output Voltage Ripple
n Output Disconnects from Input When Shut Down
n Synchronous Rectification: Up to 95% Efficiency
n Inrush Current Limit
n Up to 3MHz Programmable Switching Frequency
Synchronizable to External Clock
n Selectable Burst Mode® Operation: 25µA IQ
n Output Overvoltage Protection
n Internal Soft-Start
n <1µA IQ in Shutdown
n 16-Lead, Thermally- Enhanced 3mm × 5mm ×
0.75mm DFN and TSSOP Packages
APPLICATIONS
n RF, Microwave Power Amplifiers
n Piezo Actuators
n Small DC Motors, Thermal Printers
n 12V Analog Rail from Battery, 5V, or Backup Capacitor
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.
DESCRIPTION
The LTC®3124 is a dual-phase, synchronous step-up DC/
DC converter with true output disconnect and inrush
current limiting capable of providing output voltages up
to 15V. Dual-phase operation significantly reduces peak
inductor and capacitor ripple currents, minimizing induc-
tor and capacitor size. The 2.5A per phase current limit,
along with the ability to program output voltages up to 15V
make the LTC3124 well suited for a variety of demanding
applications. Once started, operation will continue with
inputs down to 500mV.
The LTC3124 switching frequency can be programmed
from 100kHz to 3MHz to optimize applications for highest
efficiency or smallest solution footprint. The oscillator can
be synchronized to an external clock for noise sensitive
applications. Selectable Burst Mode operation reduces
quiescent current to 25µA, ensuring high efficiency across
the entire load range. An internal soft-start limits inrush
current during start-up.
Other features include a <1µA shutdown current and robust
protection under short-circuit,thermal overload,and output
overvoltage conditions. The LTC3124 is offered in both
16-lead DFN and thermally-enhanced TSSOP packages.
TYPICAL APPLICATION
5V to 12V Synchronous Boost Converter
VIN
5V
4.7µH
SWB CAP
100nF
VOUT
4.7µH
PGNDB
SWA
VOUTB
VOUTA
22µF
×2
12V
1.5A
LTC3124
PGNDA
VIN SGND
BURST PWM
10µF
4.7µF
PWM/SYNC
VCC
RT
28k
SD
FB
VC
OFF ON
84.5k
680pF
1.02M
113k
56pF
3124 TA01a
Efficiency Curve
100
90
Burst Mode
OPERATION
80
10
1
70 PWM
60
0.1
50
40
30
20
10
0
0.01
Burst Mode
OPERATION
0.01
PWM
fSW = 1MHz 0.001
EFFICIENCY
POWER LOSS
0.0001
0.1 1 10 100 1000
LOAD CURRENT (mA)
3124 TA01b
For more information www.linear.com/LTC3124
3124f
1
1 page  
LTC3124
TYPICAL PERFORMANCE CHARACTERISTICS
Configured as front page application at TA = 25°C, unless otherwise specified.
PWM Mode Maximum Output
Current vs VIN
4.0
3.6
VOUT = 5V
VOUT = 7.5V
3.2
VOUT = 12V
VOUT = 15V
2.8
2.4
2.0
1.6
1.2
Peak Current Limit Change
vs Temperature
2
1
0
–1
–2
0.8 –3
0.4
0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
VIN (V)
3124 G10
–4
–50
–10 30
70 110 150
TEMPERATURE (°C)
3124 G11
Burst Mode Output Current vs VIN
400
350
300
250
Burst Mode No-Load Input
Current vs VIN
10000
1000
VOUT = 15V
VOUT = 12V
VOUT = 7.5V
VOUT = 5V
VOUT = 2.5V
200
150 100
100
50
0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
VIN, FALLING (V)
3124 G13
VOUT = 2.5V
VOUT = 5V
VOUT = 7.5V
VOUT = 12V
VOUT = 15V
10
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
VIN, FALLING (V)
3124 G14
PWM Operation No-Load Input
Current vs VIN
200
180
VOUT = 15V
VOUT = 12V
160
VOUT = 7.5V
VOUT = 5V
140 VOUT = 2.5V
120
100
80
60
40
20
0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
VIN (V)
3124 G12
Burst Mode Quiescent Current
Change vs Temperature
75
60
45
30
15
0
–15
–50
–10 30
70 110 150
TEMPERATURE (°C)
3124 G15
SD Pin Threshold
RT vs Frequency
VOUT
5V/DIV
900mV
VSD
500mV/DIV
400mV
1s/DIV
3124 G16
100
10
10
100
1000
FREQUENCY (kHz)
3000
3124 G17
For more information www.linear.com/LTC3124
3124f
5
5 Page 
LTC3124
OPERATION
SWITCH A
VOLTAGE
SWITCH B
VOLTAGE
INDUCTOR A
CURRENT
INDUCTOR B
CURRENT
INPUT
CURRENT
RECTIFIER A
CURRENT
RECTIFIER B
CURRENT
OUTPUT
RIPPLE
CURRENT
3124 F02
Figure 2. Simplified Voltage and Current Waveforms
for 2-Phase Operation at 50% Duty Cycle
SWITCH A
VOLTAGE
SWITCH B
VOLTAGE
INDUCTOR A
CURRENT
INDUCTOR B
CURRENT
INPUT
CURRENT
RECTIFIER A
CURRENT
LOW VOLTAGE OPERATION
The LTC3124 is designed to allow start-up from input
voltages as low as 1.8V. When VOUT exceeds 2.5V, the
LTC3124 continues to regulate its output, even when VIN
falls as low as 0.5V. This feature extends operating times
by maximizing the amount of energy that can be extracted
from the input source. The limiting factors for the applica-
tion become the availability of the power source to supply
sufficient power to the output at the low input voltage,
and the maximum duty cycle, which is clamped at 94%.
Note that at low input voltages, small voltage drops due
to series resistance become critical and greatly limit the
power delivery capability of the converter.
LOW NOISE FIXED FREQUENCY OPERATION
Soft-Start
The LTC3124 contains internal circuitry to provide soft-
start operation. The soft-start utilizes a linearly increasing
ramp of the error amplifier reference voltage from zero
to its nominal value of 1.2V in approximately 10ms, with
the internal control loop driving VOUT from zero to its
final programmed value. This limits the inrush current
drawn from the input source. As a result, the duration
of the soft-start is largely unaffected by the size of the
output capacitor or the output regulation voltage. The
closed-loop nature of the soft-start allows the converter
to respond to load transients that might occur during
the soft-start interval. The soft-start period is reset by a
shutdown command on SD, a UVLO event on VCC (VCC <
1.5V), an overvoltage event on VOUT (VOUT ≥ 16.5V), or
an overtemperature event (TSD is invoked when the die
temperature exceeds 170°C). Upon removal of these fault
conditions, the LTC3124 will soft-start the output voltage.
RECTIFIER B
CURRENT
Error Amplifier
OUTPUT
RIPPLE
CURRENT
3124 F03
Figure 3. Simplified Voltage and Current Waveforms
for 2-Phase Operation at 25% Duty Cycle
The noninverting input of the transconductance error
amplifier is internally connected to the 1.2V reference and
the inverting input is connected to FB. An external resistive
voltage divider from VOUT to SGND programs the output
voltage from 2.5V to 15V via FB as shown in Figure 4.
VOUT
=
1.2V
1+
R1
R2
For more information www.linear.com/LTC3124
3124f
11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTC3124HFE.PDF ] | |
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