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PDF LT3460-1 Data sheet ( Hoja de datos )
| Número de pieza | LT3460-1 | |
| Descripción | 1.3 MHz/650kHz Step-Up DC/DC Converter | |
| Fabricantes | Linear | |
| Logotipo |  |
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FEATURES
n 1.3MHz (LT3460) Switching Frequency
n 650kHz (LT3460-1) Switching Frequency
n High Output Voltage: Up to 36V
n 300mA Integrated Switch (LT3460)
n 180mA Integrated Switch (LT3460-1)
n Wide Input Range: 2.5V to 16V
n Uses Small Surface Mount Components
n Low Shutdown Current: <1μA
n Low Profile (1mm) SC70 (LT3460 and LT3460-1),
SOT-23 (ThinSOT™) (LT3460) and 2mm × 2mm DFN
(LT3460-1) Packages
APPLICATIONS
n Digital Cameras
n CCD Bias Supply
n XDSL Power Supply
n TFT-LCD Bias Supply
n Local 5V or 12V Supply
n Medical Diagnostic Equipment
n Battery Backup
LT3460/LT3460-1
1.3 MHz/650kHz Step-Up
DC/DC Converter in SC70,
ThinSOT and DFN
DESCRIPTION
The LT®3460/LT3460-1 are general purpose step-up DC/
DC converters. The LT3460/LT3460-1 switch at 1.3MHz/
650kHz, allowing the use of tiny, low cost and low height
capacitors and inductors. The constant frequency results
in low, predictable output noise that is easy to filter.
The high voltage switches in the LT3460/LT3460-1 are
rated at 38V, making the device ideal for boost converters
up to 36V. The LT3460 can generate 12V at up to 70mA
from a 5V supply.
The low 1mA quiescent current and 650kHz switching
frequency of LT3460-1 make it ideal for lower current
applications.
The LT3460 is available in SC70 and SOT-23 packages.
The LT3460-1 is available in SC70 and 2mm × 2mm DFN
packages.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is
a trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
TYPICAL APPLICATION
5V to 12V, 70mA Step-Up DC/DC Converter
22μH
VIN
5V
4.7μF
OFF ON
VIN SW
LT3460
SHDN
FB
GND
130k
22pF
VOUT
12V
70mA
1μF
15k
3460 F01
Efficiency
90
85
80
75
70
65
60
0
20 40
60
LOAD CURRENT (mA)
80
3460 F01a
Switching Waveforms
VSW
5V/DIV
IL
100mA/DIV
0.2μs/DIV
3460 F01b
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1
1 page  
LT3460/LT3460-1
BLOCK DIAGRAM
VIN
VOUT
1.255V
REFERENCE
R1 (EXTERNAL)
FB
R2 (EXTERNAL)
+
A1
–
FB
RS (EXTERNAL)
SHUTDOWN
SHDN
CS (EXTERNAL)
RS, CS OPTIONAL SOFT-START COMPONENTS
COMPARATOR
DRIVER
–
RC A2
+
CC
RQ
S
+
RAMP
GENERATOR
–
1.3MHz
OSCILLATOR
Figure 1. Block Diagram, LT3460
SW
Q1
0.1Ω
GND
3460 BD
OPERATION
The LT3460/LT3460-1 uses a constant frequency, current
mode control scheme to provide excellent line and load
regulation. Operation can be best understood by referring to
the block diagram in Figure 1. At the start of each oscillator
cycle, the SR latch is set, which turns on the power switch
Q1. A voltage proportional to the switch current is added
to a stabilizing ramp and the resulting sum is fed into the
positive terminal of the PWM comparator A2. When this
voltage exceeds the level at the negative input of A2, the
SR latch is reset turning off the power switch. The level at
the negative input of A2 is set by the error amplifier A1, and
is simply an amplified version of the difference between
the feedback voltage and the reference voltage of 1.255V.
In this manner, the error amplifier sets the correct peak
current level to keep the output in regulation. If the error
amplifier’s output increases, more current is delivered to
the output; if it decreases, less current is delivered.
Feedback Loop Compensation
The LT3460/LT3460-1 has an internal feedback compensa-
tion network as shown in Figure 1 (RC and CC). However,
because the small signal characteristics of a boost converter
change with operation conditions, the internal compensa-
tion network cannot satisfy all applications. A properly
designed external feed forward capacitor from VOUT to
FB (CF in Figure 2) will correct the loop compensation for
most applications.
The LT3460/LT3460-1 uses peak current mode control.
The current feedback makes the inductor very similar
to a current source in the medium frequency range. The
power stage transfer function in the medium frequency
range can be approximated as:
GP(s)
=
K1
s • C2
,
where C2 is the output capacitance, and K1 is a constant
based on the operating point of the converter. In continuous
current mode, K1 increases as the duty cycle decreases.
The internal compensation network RC, CC can be ap-
proximated as follows in medium frequency range:
GC(s)
=
K2
•
s
•
RC • CC
s • CC
+
1
The zero
fZ
=
2
•
•
1
RC
•
CC
is about 70kHz.
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5
5 Page 
PACKAGE DESCRIPTION
0.47 0.65
MAX REF
SC6 Package
6-Lead Plastic SC70
(Reference LTC DWG # 05-08-1638)
1.16 REF
LT3460/LT3460-1
1.80 – 2.20
(NOTE 4)
3.26 MAX 2.1 REF
0.96 MIN
1.80 – 2.40 1.15 – 1.35
(NOTE 4)
INDEX AREA
(NOTE 6)
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.10 – 0.40
PIN 1
0.65 BSC
0.80 – 1.00
1.00 MAX
0.15 – 0.30
6 PLCS (NOTE 3)
0.00 – 0.10
REF
0.10 – 0.30
0.10 – 0.18
NOTE:
(NOTE 3)
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. DETAILS OF THE PIN 1 INDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE INDEX AREA
7. EIAJ PACKAGE REFERENCE IS EIAJ SC-70
SC6 SC70 0802
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703)
0.675 ±0.05
R = 0.115
TYP
0.56 ± 0.05
(2 SIDES)
4
0.38 ± 0.05
6
2.50 ±0.05
1.15
±0.05
0.61 ±0.05
(2 SIDES)
PACKAGE PIN 1 BAR
OUTLINE TOP MARK
(SEE NOTE 6)
0.25 ± 0.05
0.50 BSC
1.42 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.200 REF
2.00 ±0.10
(4 SIDES)
0.75 ±0.05
0.00 – 0.05
PIN 1
CHAMFER OF
EXPOSED PAD
31
(DC6) DFN 1103
0.25 ± 0.05
0.50 BSC
1.37 ±0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LT3460-1.PDF ] | |
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