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PDF LTC3217 Data sheet ( Hoja de datos )
| Número de pieza | LTC3217 | |
| Descripción | 600mA Low Noise Multi-LED Camera Light Charge Pump | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
■ Charge Pump Provides High Efficiency with
Automatic Mode Switching
■ Multimode Operation: 1x, 1.5x, 2x
■ Four Low Dropout LED Outputs
■ Up to 600mA Total Output Current
■ Independent Torch and Flash ISET and Enable Pins
■ Low Noise Constant Frequency Operation*
■ PWM Brightness Control via the EN2 Pin
■ Low Shutdown Current: 4µA
■ Internal Soft-Start Limits Inrush Current During
Start-Up and Mode Switching
■ Open/Short LED Protection
■ No Inductors
■ (3mm x 3mm) 16-Lead QFN Plastic Package
U
APPLICATIO S
■ Multi-LED Camera Light Supply for Cellphones/
DSCs/PDAs
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. Patents, including 6411531
LTC3217www.DataSheet4U.com
600mA Low Noise
Multi-LED Camera Light
Charge Pump
DESCRIPTIO
The LTC®3217 is a low noise charge pump DC/DC con-
verter designed to power four high current LEDs. The
LTC3217 requires only four small ceramic capacitors and
two current set resistors to form a complete LED power
supply and current controller.
Built-in soft-start circuitry prevents excessive inrush cur-
rent during start-up and mode changes. High switching
frequency enables the use of small external capacitors.
Independent high and low current settings are programmed
by two external resistors. Shutdown mode and current
output levels are selected via two logic inputs.
The current through the LEDs is programmed via ISET1 and
ISET2. In addition, the brightness can be controlled by
pulse width modulation of the EN2 pin.
The charge pump optimizes efficiency based on the volt-
age across the LED current sources. The part powers up
in 1x mode and will automatically switch to boost mode
whenever any enabled LED current source begins to enter
dropout. The first dropout switches the part into 1.5x
mode and a subsequent dropout switches the part into 2x
mode. The LTC3217 resets to 1x mode whenever the part
is shut down.
The LTC3217 is available in a low profile 16-lead (3mm ×
3mm × 0.75mm) QFN package.
TYPICAL APPLICATIO
C2
2.2µF
C3
2.2µF
VBAT
C1
2.2µF
EN1 (TORCH)
EN2 (FLASH)
C1P C1M C2P C2M
VBAT
CPO
LTC3217
EN1
EN2
ISET1
ISET2
LED1
LED2
LED3
LED4
GND
19.6k
1%
6.49k
1%
C4
2.2µF
AOT-2015HPW-1751B
EN1 EN2
ILED
0 0 0 (SHUTDOWN)
10
25mA/LED
01
75mA/LED
1 1 100mA/LED
3217 TA01
Efficiency vs VBAT
100
90 100mA 200mA
80
400mA
70
60
50
40
30
20
TOTAL OUTPUT CURRENT
10 PLED/PIN
LED = 2015 HPW AOT
0
3 3.2 3.4 3.6 3.8 4 4.2 4.4
VBAT (V)
3217 G09
3217f
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LTC3217www.DataSheet4U.com
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted.
1.5x Mode CPO Voltage
vs Load Current
4.8
C2 = C3 = C4 = 2.2µF
4.6
3.4V
4.4 3.5V
3.6V
4.2
3.3V
4.0
3.2V
3.8
3.6
0
3.1V
VBAT = 3V
100 200 300 400
LOAD CURRENT (mA)
500
3217 G13
2x Mode CPO Voltage
vs Load Current
5.2
C2 = C3 = C4 = 2.2µF
5.1
5.0
3.6V
4.9
4.8
3.3V
4.7
3.2V
4.6
3.1V
4.5
VBAT = 3V
4.4
4.3
4.2
0
100 200 300 400
LOAD CURRENT (mA)
500
3217 G14
PI FU CTIO S
C1P, C2P, C1M, C2M (Pins 1, 16, 14, 12): Charge Pump
Flying Capacitor Pins. A 2.2µF X7R or X5R ceramic capaci-
tor should be connected from C1P to C1M and C2P to C2M.
CPO (Pin 2): Output of the charge pump used to power all
LEDs. This pin is enabled or disabled using the EN1 and
EN2 inputs. A 2.2µF X5R or X7R ceramic capacitor should
be connected to ground.
EN1, EN2 (Pins 3, 11): Inputs. The EN1 and EN2 pins are
used to select which current level is being supplied to the
LEDs, as well as to put the part into shutdown mode. The
truth table for these pins is as follows:
Truth Table
EN1
0
1
0
1
EN2 MODE
0 Shutdown
0 Low Current
1 High Current
1 Low + High Current
EN2 can be used for PWM of the LED currents. For proper
operation, the minimum pulse width should be 50µs and
the maximum low time should be 1ms if EN1 is low. If EN1
is high then the 1ms low time limitation does not apply.
LED1, LED2, LED3, LED4 (Pins 4, 5, 6, 7): LED1 to LED4
are the current source outputs. Each LED is connected in
between CPO (anodes) and LED1 – 4 (cathodes). The
current to each LED output is set via the EN1 and EN2
inputs, and the programming resistors connected from
ISET1 and ISET2 to GND. Any of the four LED outputs can
be disabled by connecting the output directly to CPO.
10µA of current will flow through each directly connected
LED output. For single LED applications, all four LED pins
may be tied together and will accurately share current.
GND2 (Pin 8): Analog Ground. This pin should be
connected directly to a low impedance ground plane.
ISET1/ISET2 (Pins 9, 10): LED Current Programming
Resistor Pins. The ISET1 and ISET2 pins will servo to 1.22V.
Resistors connected between each of these pins and GND
are used to set the high and low LED current levels.
Connecting a resistor 2k or less will cause the LTC3217 to
enter over-current shutdown.
GND1 (Pin 13): Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
VBAT (Pin 15): Supply Voltage. This pin should be
bypassed with a 2.2µF, or greater low ESR ceramic
capacitor.
Exposed Pad (Pin 17): This pad should be connected
directly to a low impedance ground plane for optimal
thermal and electrical performance.
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LTC3217www.DataSheet4U.com
APPLICATIO S I FOR ATIO
At moderate to high output power, the quiescent current
of the LTC3217 is negligible and the expression shown in
Equation 6 is valid.
Once dropout is detected at the LED pin, the LTC3217
enables the charge pump in 1.5x mode.
In 1.5x boost mode, the efficiency is similar to that of a
linear regulator with an effective input voltage of 1.5 times
the actual input voltage. This is because the input current
for a 1.5x charge pump is approximately 1.5 times the load
current. In an ideal 1.5x charge pump, the power
efficiency would be given by:
ηIDEAL
=
PLED
PIN
=
(VLED • ILED)
(VBAT • (1.5) • ILED)
=
VLED
(1.5 • VBAT
)
(7)
Similarly, 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) = VLED
(VBAT • (2) • ILED) (2 • VBAT )
(8)
Thermal Management
For higher input voltages and maximum output current,
there can be substantial power dissipation in the LTC3217.
If the junction temperature increases above approxi-
mately 150°C the thermal shutdown circuitry will auto-
matically deactivate the output current sources and charge
pump. To reduce maximum junction temperature, 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 will
reduce the thermal resistance of the package and PC
board considerably.
PACKAGE DESCRIPTIO
UD Package
16-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1691)
3.50 ± 0.05
1.45 ± 0.05
2.10 ± 0.05 (4 SIDES)
0.70 ±0.05
3.00 ± 0.10
(4 SIDES)
PIN 1
TOP MARK
(NOTE 6)
0.75 ± 0.05
BOTTOM VIEW—EXPOSED PAD
R = 0.115
TYP
15 16
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
0.40 ± 0.10
1.45 ± 0.10
(4-SIDES)
1
2
PACKAGE
OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-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
0.200 REF
0.00 – 0.05
(UD16) QFN 0904
0.25 ± 0.05
0.50 BSC
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
3217f
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11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LTC3217.PDF ] | |
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