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PDF LT3467 Data sheet ( Hoja de datos )
| Número de pieza | LT3467 | |
| Descripción | 1.1A Step-Up DC/DC Converter | |
| Fabricantes | Linear | |
| Logotipo |  |
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FEATURES
n 1.3MHz Switching Frequency (LT3467)
n 2.1MHz Switching Frequency (LT3467A)
n Low VCESAT Switch: 330mV at 1.1A
n High Output Voltage: Up to 40V
n Wide Input Range: 2.4V to 16V
n Dedicated Soft-Start Pin
n 5V at 540mA from 3.3V Input (LT3467)
n 5V at 430mA from 3.3V Input (LT3467A)
n 12V at 270mA from 5V Input (LT3467)
n 12V at 260mA from 5V Input (LT3467A)
n Uses Small Surface Mount Components
n Low Shutdown Current: <1μA
n Pin-for-Pin Compatible with the LT1930 and LT1613
n Low Profile (1mm) ThinSOT™ Package
n Low Profile (0.75mm) 8-Lead (3mm × 2mm)
DFN Package
APPLICATIONS
n Digital Cameras
n White LED Power Supplies
n Cellular Phones
n Medical Diagnostic Equipment
n Local 5V or 12V Supplies
n TFT-LCD Bias Supplies
n xDSL Power Supplies
LT3467/LT3467A
1.1A Step-Up DC/DC
Converter with
Integrated Soft-Start
DESCRIPTION
The LT®3467/LT3467A switching regulators combine a
42V, 1.1A switch with a soft-start function. Pin compatible
with the LT1930, its low VCESAT bipolar switch enables the
device to deliver high current outputs in a small footprint.
The LT3467 switches at 1.3MHz, allowing the use of tiny,
low cost and low height inductors and capacitors. The
LT3467A switches at 2.1MHz, allowing the use of even
smaller components. High inrush current at start-up is
eliminated using the programmable soft-start function.
A single external capacitor sets the current ramp rate. A
constant frequency current mode PWM architecture results
in low, predictable output noise that is easy to filter.
The high voltage switch on the LT3467/LT3467A is rated
at 42V, making the devices ideal for boost converters up
to 40V as well as SEPIC and flyback designs. The LT3467
can generate 5V at up to 540mA from a 3.3V supply or
5V at 450mA from four alkaline cells in a SEPIC design.
The LT3467A can generate 5V at up to 430mA from a 3.3V
supply or 15V at 135mA from a 3.3V supply. The LT3467/
LT3467A are available in a low profile (1mm) 6-lead SOT-23
package and tiny 3mm × 2mm DFN package.
L, LT, LTC, LTM, Linear Technology and the Linear logo 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
VIN
2.6V TO
4.2V
Single Li-Ion Cell to 5V Boost Converter
2.7μH
4.7μF
OFF ON
0.047μF
VIN SW
SHDN
LT3467
SS FB
GND
402k
3.3pF
VOUT
5V
765mA AT VIN = 4.2V,
540mA AT VIN = 3.3V,
360mA AT VIN = 2.6V
133k
15μF
3467 TA01a
Efficiency
95
90
85 VIN = 4.2V
VIN = 3.3V
80 VIN = 2.6V
75
70
65
60
55
50
100 200 300 400 500 600 700 800 900
IOUT (mA)
3467 TA01b
3467afe
1
1 page  
LT3467/LT3467A
PIN FUNCTIONS (DFN/TSOT)
FB (Pin 1/Pin 3): Feedback Pin. Reference voltage is 1.255V.
Connect resistive divider tap here. Minimize trace area at
FB. Set VOUT = 1.255V(1 + R1/R2).
GND (Pins 2, 5, 9/Pin 2): Ground. Tie directly to local
ground plane.
SW (Pins 3, 4/Pin 1): Switch Pin. (Collector of internal
NPN power switch) Connect inductor/diode here and
minimize the metal trace area connected to this pin to
minimize EMI.
VIN (Pin 6/Pin 6): Input Supply Pin. Must be locally
bypassed.
SS (Pin 7/Pin 5): Soft-Start Pin. Place a soft-start capacitor
here. Upon start-up, 4μA of current charges the capacitor
to 1.255V. Use a larger capacitor for slower start-up. Leave
floating if not in use.
SHDN (Pin 8/Pin 4): Shutdown Pin. Tie to 2.4V or more
to enable device. Ground to shut down.
BLOCK DIAGRAM
SS
VIN
1.255V
REFERENCE
VOUT
R1 (EXTERNAL)
FB
R2 (EXTERNAL)
250k
+
A1
–
SHUTDOWN
SHDN
FB
– COMPARATOR
RC
A2
+
RQ
S
CC
3
RAMP
GENERATOR
1.3MHz
OSCILLATOR*
*2.1MHz FOR LT3467A
SW
DRIVER
Q1
+
0.01Ω
–
GND
3467 F01
Figure 1. Block Diagram
3467afe
5
5 Page 
LT3467/LT3467A
APPLICATIONS INFORMATION
Using the circuit of Figure 2 as an example, the following
table shows the parameters used to generate the Bode
plot shown in Figure 7.
50
40
30
20
10
0
–10
–20
–30
–40
–50
100
GAIN
PHASE
1k 10k 100k
FREQUENCY (Hz)
0
–45
–90
–135
–180
–225
–270
–315
–360
–405
–450
1M
3467 F07
Figure 7. Bode Plot of 3.3V to 5V Application
Table 3. Bode Plot Parameters
PARAMETER VALUE
UNITS
RL 10.4
COUT
15
RESR
10
RO 0.4
CC 60
CPL 3.3
RC 100
R1 402
Ω
μF
mΩ
MΩ
pF
pF
kΩ
kΩ
R2 133 kΩ
VOUT
5
V
VIN 3.3
V
gma 35 μmho
gmp 7.5 mho
L 2.7 μH
fS 1.3*
*2.1MHz for LT3467A
MHz
COMMENT
Application Specific
Application Specific
Application Specific
Not Adjustable
Not Adjustable
Adjustable
Not Adjustable
Adjustable
Adjustable
Application Specific
Application Specific
Not Adjustable
Not Adjustable
Application Specific
Not Adjustable
From Figure 7, the phase is –138° when the gain reaches
0dB giving a phase margin of 42°. This is more than
adequate. The crossover frequency is 37kHz.
TYPICAL APPLICATIONS
Lithium-Ion to 6V Step-Up DC/DC Converter
VIN
2.7V TO 4.2V
C1
2.2μF
SHDN
C4
0.047μF
L1
2.2μH
D1
VIN SW
SHDN
LT3467
SS FB
GND
R1
501k
R2
133k
C3
1.8pF
VOUT
6V
275mA AT VIN = 2.7V
490mA AT VIN = 3.8V
590mA AT VIN = 4.2V
C2
15μF
C1, C2: X5R OR X7R, 6.3V
D1: ON SEMICONDUCTOR MBRM120
L1: SUMIDA CR43-2R2
3467 TA02
Li-Ion to 6V
95
90 VIN = 4.2V
85 VIN = 3.8V
80 VIN = 2.7V
75
70
65
60
55
50
50 100 200 300 400 500 600 700
IOUT (mA)
3467 TA02b
3467afe
11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LT3467.PDF ] | |
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