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PDF LTC3616 Data sheet ( Hoja de datos )
| Número de pieza | LTC3616 | |
| Descripción | 6A 4MHz Monolithic Synchronous Step-Down DC/DC Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
n 6A Output Current
n 2.25V to 5.5V Input Voltage Range
n Low Output Ripple Burst Mode® Operation: IQ = 75μA
n ±1% Output Voltage Accuracy
n Output Voltage Down to 0.6V
n High Efficiency: Up to 95%
n Low Dropout Operation: 100% Duty Cycle
n Programmable Slew Rate on SW Node Reduces
Noise and EMI
n Adjustable Switching Frequency: Up to 4MHz
n Optional Active Voltage Positioning (AVP) with
Internal Compensation
n Selectable Pulse-Skipping/Forced Continuous/Burst
Mode Operation with Adjustable Burst Clamp
n Programmable Soft-Start
n Inputs for Start-Up Tracking or External Reference
n DDR Memory Mode, IOUT = ±3A
n Available in a 24-Pin 3mm × 5mm QFN
Thermally Enhanced Package
APPLICATIONS
n Point-of-Load Supplies
n Distributed Power Supplies
n Portable Computer Systems
n DDR Memory Termination
n Handheld Devices
LTC3616www.DataSheet4U.com
6A, 4MHz Monolithic
Synchronous Step-Down
DC/DC Converter
DESCRIPTION
The LTC®3616 is a low quiescent current monolithic syn-
chronous buck regulator using a current mode, constant
frequency architecture. The no-load DC supply current
in sleep mode is only 70μA while maintaining the output
voltage (Burst Mode operation) at no load, dropping to zero
current in shutdown. The 2.25V to 5.5V input supply voltage
range makes the LTC3616 ideally suited for single Li-Ion
as well as fixed low voltage input applications. 100% duty
cycle capability provides low dropout operation, extending
the operating time in battery-powered systems.
The operating frequency is externally programmable up to
4MHz, allowing the use of small surface mount inductors.
For switching noise-sensitive applications, the LTC3616
can be synchronized to an external clock at up to 4MHz.
Forced continuous mode operation in the LTC3616 reduces
noise and RF interference. Adjustable compensation allows
the transient response to be optimized over a wide range
of loads and output capacitors.
The internal synchronous switch increases efficiency and
eliminates the need for an external catch diode, saving
external components and board space. The LTC3616 is
offered in a leadless 24-pin 3mm × 5mm thermally en-
hanced QFN package.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6580258, 5481178, 5994885, 6304066, 6498466, 6611131.
TYPICAL APPLICATION
VIN
2.7V TO 5.5V
SVIN
PVIN
RUN SRLIM/DDR
TRACK/SS
RT/SYNC
LTC3616 SW
PGOOD
SGND
ITH PGND
MODE
VFB
210k
22μF
s4
220nH
665k
VOUT
2.5V
47μF 6A
s2
3616 TA01a
Efficiency and Power Loss
vs Load Current
100
90
80 1
70
60 0.1
50
40 0.01
30
20
10
0 VOUT = 2.5V
1 10
VIN = 2.8V
VIN = 3.3V
VIN = 5V
0
100 1000 10000
OUTPUT CURRENT (mA)
3616 TA01b
3616f
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1 page  
LTC3616www.DataSheet4U.com
TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.3V, RT/SYNC = SVIN unless otherwise noted.
Efficiency vs Input Voltage
Burst Mode Operation
(VMODE = 0V)
100
VOUT = 1.8V
90
80
70
60
50
40
30
2.5
IOUT = 6mA
IOUT = 600mA
IOUT = 2A
IOUT = 6A
3 3.5 4 4.5 5 5.5
INPUT VOLTAGE (V)
3616 G04
Efficiency vs Frequency
Burst Mode Operation
(VMODE = 0V), IOUT = 2A
95
94
93
VIN = 3.3V
VOUT = 1.8V
92
91
90
89
88
87
86
85
84 150nH
83
330nH
470nH
82
0.5 1 1.5 2 2.5 3 3.5 4 4.5
FREQUENCY (MHz)
3616 G05
Load Regulation
(VIN = 3.3V, VOUT = 1.8V)
1.5
FORCED CONTINUOUS MODE
1.3 PULSE-SKIPPING MODE
INTERNAL Burst Mode OPERATION
1.1
0.9
0.7
0.5
0.3
0.1
–0.1
–0.3
0
1000 2000 3000 4000 5000 6000
OUTPUT CURRENT (mA)
3616 G06
Line Regulation
0.3
Burst Mode Operation
0.2
0.1
VOUT
20mV/DIV
0
–0.1
–0.2
–0.3
2.20 2.75
3.30 3.85 4.40
INPUT VOLTAGE (V)
4.95 5.50
3616 G07
IL
1A/DIV
VOUT = 1.8V
IOUT = 150mA
VMODE = 0V
20μs/DIV
Forced Continuous Mode Operation
Load Step Transient in
Pulse-Skipping Mode
VOUT
20mV/DIV
VOUT
200mV/DIV
Pulse-Skipping Mode Operation
VOUT
20mV/DIV
3616 G08
IL
1A/DIV
VOUT = 1.8V
IOUT = 150mA
VMODE = 3.3V
20μs/DIV
Load Step Transient in
Burst Mode Operation
3616 G09
VOUT
200mV/DIV
IL
500mA/DIV
VOUT = 1.8V
IOUT = 100mA
VMODE = 1.5V
1μs/DIV
ILOAD
5A/DIV
3616 G10
100μs/DIV
VOUT = 1.8V
ILOAD = 100mA TO 6A
VMODE = 3.3V
COMPENSATION FIGURE 1
3616 G11
ILOAD
5A/DIV
100μs/DIV
VOUT = 1.8V
ILOAD = 100mA TO 6A
VMODE = 0V
COMPENSATION FIGURE 1
3616 G12
3616f
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5 Page 
LTC3616www.DataSheet4U.com
OPERATION
Main Control Loop
The LTC3616 is a monolithic, constant frequency, current
mode step-down DC/DC converter. During normal opera-
tion, the internal top power switch (P-channel MOSFET) is
turned on at the beginning of each clock cycle. Current in
the inductor increases until the current comparator trips
and turns off the top power switch. The peak inductor cur-
rent at which the current comparator trips is controlled by
the voltage on the ITH pin. The error amplifier adjusts the
voltage on the ITH pin by comparing the feedback signal
from a resistor divider on the VFB pin with an internal 0.6V
reference. When the load current increases, it causes a
reduction in the feedback voltage relative to the reference.
The error amplifier raises the ITH voltage until the average
inductor current matches the new load current. Typical
voltage range for the ITH pin is from 0.1V to 1.05V with
0.45V corresponding to zero current.
When the top power switch shuts off, the synchronous
power switch (N-channel MOSFET) turns on until either
the bottom current limit is reached or the next clock cycle
begins. The bottom current limit is typically set at –8A for
forced continuous mode and 0A for Burst Mode operation
and pulse-skipping mode.
The operating frequency defaults to 2.25MHz when
RT/SYNC is connected to SVIN, or can be set by an external
resistor connected between the RT/SYNC pin and ground,
or by a clock signal applied to the RT/SYNC pin. The switch-
ing frequency can be set from 300kHz to 4MHz.
Overvoltage and undervoltage comparators pull the
PGOOD output low if the output voltage varies more than
±7.5% (typical) from the set point.
Mode Selection
The MODE pin is used to select one of four different
operating modes:
Mode Selection Voltage
SVIN
SVIN – 0.3V
SVIN • 0.58
PS PULSE-SKIPPING MODE ENABLE
FC FORCED CONTINUOUS MODE ENABLE
1.1V
0.8V
0.45V
0.3V
SGND
BM
EXT
Burst Mode ENABLE—EXTERNAL CLAMP,
CONTROLLED BY VOLTAGE APPLIED AT
MODE PIN
BM Burst Mode ENABLE—INTERNAL CLAMP
3616 OP01
Burst Mode Operation—Internal Clamp
Connecting the MODE pin to SGND enables Burst Mode
operation with an internal clamp. In Burst Mode operation
the internal power switches operate intermittently at light
loads. This increases efficiency by minimizing switching
losses. During the intervals when the switches are idle,
the LTC3616 enters sleep state where many of the internal
circuits are disabled to save power. During Burst Mode
operation, the minimum peak inductor current is internally
clamped and the voltage on the ITH pin is monitored by
the burst comparator to determine when sleep mode is
enabled and disabled. When the average inductor current
is greater than the load current, the voltage on the ITH pin
drops. As the ITH voltage falls below the internal clamp,
the burst comparator trips and enables sleep mode. Dur-
ing sleep mode, the power MOSFETs are held off and the
load current is solely supplied by the output capacitor.
When the output voltage drops, the top power switch is
turned back on and the internal circuits are re-enabled.
This process repeats at a rate that is dependent on the
load current.
3616f
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11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTC3616.PDF ] | |
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