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PDF LTC3218 Data sheet ( Hoja de datos )
| Número de pieza | LTC3218 | |
| Descripción | 400mA Single Wire Camera LED Charge Pump | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC3218www.DataSheet4U.com
400mA Single Wire
Camera LED Charge Pump
FEATURES
■ Low Noise Constant-Frequency Operation
■ Multi-Mode Operation: 1x or 2x Boost Mode
■ Automatic Mode Switching
■ High Output Current: 150mA (Continuous), 400mA
(Pulsed) From Li-Ion/Polymer Input
■ 2-Second Flash Current Timeout for LED Protection
■ Automatic Soft-Start
■ Output Disconnect
■ No Inductors
■ 220mΩ Internal High Side Current Sense Resistor
■ Single Resistor Programming Capability
■ Tiny Application Circuit (3mm × 2mm DFN Package,
All Components < 1mm High)
APPLICATIONS
■ LED Torch/Flash Supply for DSCs/Cellphones
DESCRIPTION
The LTC®3218 is a low-noise, high-current charge pump
DC/DC converter capable of driving high current LEDs at up
to 400mA from a 2.9V to 4.5V input. A low external parts
count (one flying capacitor, two programming resistors and
two bypass capacitors at VIN and CPO) make the LTC3218
ideally suited for small, battery-powered applications.
Built-in soft-start circuitry prevents excessive inrush cur-
rent during start-up. High switching frequency enables the
use of small external capacitors. A built-in 2-second timer
protects the LED during flash mode.
Output current level is programmed by an external re-
sistor. LED current is regulated using an internal high
side 220mΩ sense resistor. Automatic mode switching
optimizes efficiency by monitoring the voltage across the
charge pump and switching modes only when dropout
is detected. The part is available in a low profile 3mm ×
2mm 10-lead DFN package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 6411531.
TYPICAL APPLICATION
2.2µF
2.9V TO 4.5V
2.2µF
DISABLED ENABLED
DISABLED ENABLED
ENF ENT
ILED
0 0 0 (SHUTDOWN)
0 1 100mA (TORCH)
1 0 290mA
1 1 390mA (FLASH)
CP
VIN
CM
CPO
LTC3218
ENF
ENT
ISETF
ILED
GND
ISETT
10.2k
1%
4.7µF
LED
AOT2015
3218 TA01
Efficiency vs VIN
100
90
80
70
60
50 50mA
150mA
300mA
40
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VIN (V)
3218 TA01b
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LTC3218www.DataSheet4U.com
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Efficiency vs VIN
100
90
80
70
60 50mA
100mA
50 150mA
200mA
300mA
40
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VIN (V)
3218 G13
2x Mode CPO Output Ripple
50mV/DIV
AC COUPLED
VIN = 3.6V
ICPO = 200mA
500ns/DIV
3218 G14
PIN FUNCTIONS
CP, CM (Pin 1, Pin 9): Charge Pump Flying Capacitor. A
2.2µF X5R or X7R ceramic capacitor should be connected
from CP to CM.
CPO (Pin 2): Output of the Charge Pump. This pin may
be enabled or disabled using the ENT and ENF inputs.
A 4.7µF X5R or X7R ceramic capacitor is required from
CPO to GND.
ILED (Pin 3): LED Current Output. The LED is connected
between ILED (anode) and GND (cathode). The current
out of the ILED pin is set by resistors connected to the
ISETT and ISETF pins. An internal, 220mΩ sense resistor
is connected between CPO and ILED
ENT (Pin 4): Input. The ENT pin is used to enable the
part into torch mode and bring it into shutdown mode.
An internal 250kΩ resistor pulls this pin to GND when
left floating.
ISETT (Pin 5): LED Torch Current Programming Resistor.
A resistor connected between this pin and GND is used
to set the LED torch current level.
ISETF (Pin 6): LED Flash Current Programming Resistor.
A resistor connected between this pin and GND is used
to set the LED flash current level.
ENF (Pin 7): Input. The ENF pin is used to enable the
part into flash mode and bring it into shutdown mode.
An internal 250kΩ resistor pulls this pin to GND when
left floating. A safety timer will disable the part if this pin
is held high for more than 2 seconds.
GND (Pin 8): Ground. This pin should be connected directly
to a low impedance ground plane.
VIN (Pin 10): Power. Supply voltage for the LTC3218. VIN
should be bypassed with a low impedance ceramic capaci-
tor to GND of at least 1.6µF of capacitance.
Exposed Pad (Pin 11): Ground. This pad must be soldered
to a low impedance ground plane for optimum thermal
performance.
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APPLICATIONS INFORMATION
At moderate to high output power, the quiescent current
of the LTC3218 is negligible and the expression above is
valid.
Once dropout is detected at the ILED pin, the LTC3218
enables the charge pump in 2x mode.
In 2x boost mode, the efficiency is similar to that of a
linear regulator with an effective input voltage of 2 times
the actual input voltage. In an ideal 2x charge pump, the
power efficiency would be given by:
ηIDEAL
≡
PLED
PIN
=
VLED • ILED
VIN • 2 • ILED
≈
VLED
2VIN
Thermal Management
For higher input voltages and maximum output current,
there can be substantial power dissipation in the LTC3218.
If the junction temperature increases above approximately
165°C, the thermal shutdown circuitry will automatically
deactivate the output. To reduce maximum junction tem-
perature, a good thermal connection to the PC board is
recommended. Connecting the Exposed Pad to a ground
plane and maintaining a solid ground plane under the
device can reduce the thermal resistance of the package
and PC board considerably.
PACKAGE DESCRIPTION
DDB Package
10-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1722 Rev Ø)
0.64 ±0.05
(2 SIDES)
2.55 ±0.05
1.15 ±0.05
0.70 ±0.05
0.25 ± 0.05
0.50 BSC
2.39 ±0.05
(2 SIDES)
PACKAGE
OUTLINE
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
3.00 ±0.10
(2 SIDES)
R = 0.05
TYP
R = 0.115
TYP
6
0.40 ± 0.10
10
2.00 ±0.10
(2 SIDES)
0.75 ±0.05
0.64 ± 0.05
(2 SIDES)
5
0.25 ± 0.05
PIN 1
R = 0.20 OR
0.25 × 45°
CHAMFER
1 (DDB10) DFN 0905 REV Ø
0.50 BSC
0 – 0.05
2.39 ±0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
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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| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC3218.PDF ] | |
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