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PDF LTC3612 Data sheet ( Hoja de datos )
| Número de pieza | LTC3612 | |
| Descripción | 4MHz Monolithic Synchronous Step-Down DC/DC Converter | |
| Fabricantes | Linear | |
| Logotipo |  |
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FEATURES
n 3A Output Current
n 2.25V to 5.5V Input Voltage Range
n Low Output Ripple Burst Mode® Operation: IQ = 70µA
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 Shutdown Current: ≤1µA
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 = ±1.5A
n Available in Thermally Enhanced 20-Pin
(3mm × 4mm) QFN and TSSOP Packages
APPLICATIONS
n Point-of-Load Supplies
n Distributed Power Supplies
n Portable Computer Systems
n DDR Memory Termination
n Handheld Devices
LTC3612
3A, 4MHz Monolithic
Synchronous Step-Down
DC/DC Converter
DESCRIPTION
The LTC®3612 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 LTC3612 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 LTC3612
can be synchronized to an external clock at up to 4MHz.
Forced continuous mode operation in the LTC3612 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 LTC3612 is
offered in a leadless 20-pin 3mm × 4mm QFN or a thermally
enhanced 20-pin TSSOP package.
L, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo 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
2.5V TO 5.5V
SVIN
RUN
TRACK/SS
PVIN
PVIN_DRV
DDR
RT/SYNC
LTC3612 SW
PGOOD
SGND
ITH PGND
MODE
VFB
210k
22µF
×2
560nH
47µF
VOUT
2.5V
3A
665k
3612 TA01a
Efficiency and Power Loss vs Load Current
100 10
90
80 1
70
60 0.1
50
40 0.01
30
20
10
0
1
VIN = 5V
VIN = 3.3V
VIN = 2.8V
0.001
10 100 1000 10000
OUTPUT CURRENT (mA) 3612 TA01b
For more information www.linear.com/LTC3612
3612fb
1
Free Datasheet http://www.nDatasheet.com
1 page  
LTC3612
TYPICAL PERFORMANCE CHARACTERISTICS VIN = 3.3V, RT/SYNC = SVIN, unless otherwise noted.
Efficiency vs Load Current
(VMODE = 0V)
100
90
VOUT = 1.8V
80
70
60
50
40
30
20
10
0
1
VIN = 5V
VIN = 3.3V
VIN = 2.5V
10 100 1000
OUTPUT CURRENT (mA)
10000
3612 G01
Efficiency vs Load Current
(VMODE = 0V)
100
90
VOUT = 1.2V
80
70
60
50
40
30
20
10
0
1
VIN = 5V
VIN = 3.3V
VIN = 2.5V
10 100 1000
OUTPUT CURRENT (mA)
10000
3612 G02
Efficiency vs Load Current
100
90 VOUT = 1.8V
80
70
Burst Mode
EXTERNAL
60 CLAMP = 0.7V
50
Burst Mode
INTERNAL
40 CLAMP
PULSE-
30 SKIPPING
20
MODE
FORCED
10 CONTINUOUS
MODE
0
1 10 100 1000 10000
OUTPUT CURRENT (mA)
3612 G03
Efficiency vs Input Voltage
(VMODE = 0V)
100 VOUT = 1.8V
90
80
70
60
50
IOUT = 3mA
40
IOUT = 300mA
IOUT = 1A
IOUT = 3A
30
2.25 2.75 3.25 3.75 4.25 4.75 5.25
INPUT VOLTAGE (V)
3612 G04
Efficiency vs Frequency
(VMODE = 0V), IOUT = 1A
95
94
VOUT = 1.8V
93
92
91
90
89
88
87
86
85
84
83
1µH
0.68µH
0.33µH
82
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
FREQUENCY (MHz)
3612 G05
Load Regulation
1.5 FORCED CONTINUOUS MODE
1.3 INTERNAL Burst Mode OPERATION
PULSE-SKIPPING MODE
1.1
0.9
0.7
0.5
0.3
0.1
–0.1
VOUT = 1.8V
–0.3
0 500 1000
1500
2000
2500
OUTPUT CURRENT (mA)
3000
3612 G06
Line Regulation
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
2.20 2.75
3.30 3.85 4.40
INPUT VOLTAGE (V)
4.95 5.50
3612 G07
Burst Mode Operation
VOUT
20mV/DIV
IL
500mA/DIV
VOUT = 1.8V
IOUT = 75mA
VMODE = 0V
20µs/DIV
3612 G08
For more information www.linear.com/LTC3612
3612fb
5
Free Datasheet http://www.nDatasheet.com
5 Page 
FUNCTIONAL BLOCK DIAGRAM
LTC3612
SVIN SGND
RT/SYNC
ITH
ITH SENSE
PVIN
PVIN_DRV
COMPARATOR
+
RUN
BANDGAP
AND
OSCILLATOR
BIAS
SVIN – 0.3V
–
INTERNAL
COMPENSATION
CURRENT
SENSE
R
–
+
VFB
TRACK/SS
ITH
LIMIT
PMOS CURRENT
COMPARATOR
+
–
0.3V
+
FOLDBACK
AMPLIFIER
0.6V +
–
SOFT-START
ERROR
AMPLIFIER
BURST
– COMPARATOR
SLEEP
+
+
MODE
–
SLOPE
COMPENSATION
DRIVER
PGOOD
0.555V +
–
+
0.645V –
LOGIC
REVERSE
COMPARATOR
IREV
+
–
DDR MODE
SW
SW
SW
SW
PGND
EXPOSED PAD
3612 BD
For more information www.linear.com/LTC3612
3612fb
11
Free Datasheet http://www.nDatasheet.com
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC3612.PDF ] | |
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