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PDF LTC3415 Data sheet ( Hoja de datos )
| Número de pieza | LTC3415 | |
| Descripción | 7A PolyPhase Synchronous Step-Down Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
n High Efficiency: Up to 96%
n 7A Output Current at VIN = 3V
n Adjustable Frequency: 1.5MHz Nominal
n PolyPhase Operation (Up to 12 Phases)
n Spread Spectrum Frequency Modulation
n Output Tracking and Margining
n ±1% Reference Accuracy
n 2.5V to 5.5V VIN Range
n Phase Lockable from 0.75MHz to 2.25MHz
n Selectable Burst Mode® Operation
n Low Dropout Operation: 100% Duty Cycle
n Low Quiescent Current: 450μA
n Current Mode Operation for Excellent Line and Load
Transient Response
n Shutdown Mode Draws Only 0.2μA Supply Current
n Available in 38-Pin (5mm × 7mm) QFN Package
APPLICATIONS
n Point of Load Power Supply
n Portable Instruments
n Distributed Power Systems
n Battery-Powered Equipment
LTC3415www.DataSheet4U.com
7A, PolyPhase
Synchronous Step-Down
Regulator
DESCRIPTION
The LTC®3415 is a high efficiency, monolithic synchronous
buck regulator using a phase lockable constant frequency,
current mode architecture. PolyPhase® operation allows
multiple LTC3415s to run out of phase while using mini-
mal input and output capacitance. The operating supply
range is from 5.5V down to 2.5V, making it suitable for
single Lithium-Ion battery as well as point of load power
supply applications. Burst Mode operation provides high
efficiency at low load currents. 100% duty cycle provides
low dropout operation that extends operating time in bat-
tery-operated systems.
The operating frequency is internally set at 1.5MHz, al-
lowing the use of small surface mount inductors. For
switching-noise sensitive applications, it can be externally
synchronized from 0.75MHz to 2.25MHz. The PHMODE
pin allows user control of the phase of the outgoing clock
signal. The current sense comparator is factory trimmed
for accurate output current sharing. Burst Mode operation
is inhibited during synchronization or when the MODE pin
is pulled low to reduce noise and RF interference.
, LT, LTC, LTM, Burst Mode and PolyPhase are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466,
6611131.
TYPICAL APPLICATION
VIN, 2.5V to 5.5V
CLKIN SVIN
PVIN SW
CLKOUT
SW
PHMODE
SW
PLLLPF
SW
RUN LTC3415 SW
60k TRACK
FB
MODE
PGOOD
ITH
120k
SGND
PGND
22μF
x3
0.2μH
VOUT
1.8V
47μF
x3
3415 TA01
Figure 1. High Efficiency Step-Down Converter
Efficiency and Power Loss
100
90
80
70
60
50
40
30
20
10
0
0.01
EFFICIENCY
10
1
0.1
POWER LOSS
0.1 1
LOAD CURRENT (A)
0.01
2.5V
3.3V
5V 0.001
10
3415 TA01B
3415fa
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC3415www.DataSheet4U.com
Efficiency and Power Loss
Burst Mode Operation
100
VOUT = 1.8V
90
80 EFFICIENCY
70
60
50
40 POWER LOSS
30
20
10
0
0.01 0.1
1
LOAD CURRENT (A)
10
1
0.1
0.01
2.5V
3.3V
5V 0.001
10
3415 G09
Output Tracking
VOUT2 =
3.3V/7A
500mV/DIV
VOUT1 =
1.8V/14A
500mV/DIV
500μs/DIV
3415 G07
Efficiency and Power Loss
Pulse-Skip Mode Operation
100
VOUT = 1.8V
90
EFFICIENCY
80
70
60
50
40
30 POWER LOSS
20
10
0
0.01
0.1 1
LOAD CURRENT (A)
10
1
0.1
2.5V
3.3V
5V 0.01
10
3415 G10
Switch Leakage Current
vs Input Voltage
200
175
150
125
MAIN SWITCH
100
75
50
SYNCHRONOUS
25 SWITCH
0
2.5 3 3.5 4 4.5 5 5.5 6
INPUT VOLTAGE (V)
3415 G12
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5 Page 
LTC3415www.DataSheet4U.com
OPERATION
of phases used times the output voltage). The output ripple
amplitude is also reduced by the number of phases used.
Figure 3 graphically illustrates the principle.
The worst-case RMS ripple current for a single stage design
peaks at an input voltage of twice the output voltage. The
worst case RMS ripple current for a two stage design re-
sults in peak outputs of 1/4 and 3/4 of input voltage. When
the RMS current is calculated, higher effective duty factor
results and the peak current levels are divided as long as
the current in each stage is balanced. Refer to Application
Note 19 for a detailed description of how to calculate RMS
current for the single stage switching regulator. Figures 4 and
5 illustrate how the input and output currents are reduced
by using an additional phase. For a 2-phase converter,
the input current peaks drop in half and the frequency is
doubled. The input capacitor requirement is thus reduced
theoretically by a factor of four! Just imagine the possibility
of capacitor savings with even higher number of phases!
Output Current Sharing
When multiple LTC3415s are cascaded to drive a com-
mon load, accurate output current sharing is essential to
achieve optimal performance and efficiency. Otherwise,
if one stage is delivering more current than another, then
the temperature between the two stages will be different,
and that could translate into higher switch RDS(ON), lower
efficiency, and higher RMS ripple. Each LTC3415 is trimmed
such that when the ITH pins of multiple LTC3415s are tied
SW1 V
ICIN
SINGLE PHASE
ICOUT
SW1 V
SW2 V
IL1
IL2
ICIN
ICOUT
DUAL PHASE
3415 F03
RIPPLE
Figure 3. Single and 2-Phase Current Waveforms
together, the amount of output current delivered from each
LTC3415 is nearly the same.
Different ground potentials among LTC3415 stages, caused
by physical distances and ground noises, could cause an
offset to the absolute ITH value seen by each stage. To
ensure that the ground level doesn’t affect the ITH value,
the LTC3415 uses a differential driver that takes as input
not just the ITH pin, but also the ITHM pin. The ITHM pins
of all the LTC3415 stages should be tied together and then
connected to the SGND at only one point.
1.0
0.9
0.8
1 PHASE
0.7
0.6
0.5
0.4
0.3
2 PHASE
0.2
0.1
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
DUTY FACTOR (VOUT/VIN)
3415 F04
Figure 4. Normalized Output Ripple Current vs Duty Factor
[IRMSʺ 0.3 (DIC(PP))]
0.6
1 PHASE
0.5
0.4
0.3
2 PHASE
0.2
0.1
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
DUTY FACTOR (VOUT/VIN)
3415 F05
Figure 5. Normalized RMS Input Ripple Current vs Duty Factor
for 1 and 2 Output Stages
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11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTC3415.PDF ] | |
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