Document
LTC3215 700mA Low Noise High Current LED Charge Pump
FEATURES
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DESCRIPTIO
High Efficiency Operation: 1x, 1.5x or 2x Boost Modes with Automatic Mode Switching Ultralow Dropout ILED Current Control Output Current up to 700mA Low Noise Constant Frequency Operation* Wide VIN Range: 2.9V to 4.4V Open/Shorted LED Protection LED Disconnect in Shutdown Low Shutdown Current: 2.5µA 4% LED Current Programming Accuracy Automatic Soft-Start Limits Inrush Current No Inductors Tiny Application Circuit (All Components <1mm Profile) 3mm × 3mm 10-Lead DFN Package
The LTC®3215 is a low noise, high current charge pump DC/DC converter designed to power high current LEDs. The part includes an accurate programmable current source capable of driving loads up to 700mA from a 2.9V to 4.4V input. Low external parts count (two flying capacitors, one programming resistor and two bypass capacitors) makes the LTC3215 ideally suited for small, batterypowered applications. Built-in soft-start circuitry prevents excessive inrush current during start-up. High switching frequency enables the use of small external capacitors. LED current is programmed with an external resistor. The LED is disconnected from VIN during shutdown. An ultralow dropout current source maintains accurate LED current at very low ILED voltages. Automatic mode switching optimizes efficiency by monitoring the voltage across the LED current source and switching modes only when ILED dropout is detected. The LTC3215 is available in a low profile 3mm × 3mm 10-Lead DFN package.
, LTC and LT are registered trademarks of Linear Technology Corporation. *Protected by U.S. Patent 6411531.
U APPLICATIO S
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LED Torch/Camera Light Supply for Cell Phones, PDAs and Digital Cameras General Lighting and/or Flash/Strobe Applications
TYPICAL APPLICATIO
C1 2.2µF
C2 2.2µF
100 90 EFFICIENCY (PLED/PIN) (%) ILED = 200mA
C1+ 2.9V TO 4.4V CIN 2.2µF VIN
C1– C2+
C2– CPO LED1 CCPO 4.7µF
80 70 60 50 40 30 20 10
LTC3215 ILED ILED 200mA
DISABLE ENABLE
EN ISET 20k 1%
3215 TA01a
LED = AOT2015 HPW 1751B VF = 3V TYP AT 200mA 2.8 3.0 3.2 3.4 3.6 3.8 VIN (V) 4.0 4.2 4.4
0
LED1: AOT2015 HPW 1751B
U
Efficiency vs VIN
3215 TA01b
U
3215f
1
LTC3215
ABSOLUTE
(Note 1)
AXI U RATI GS
U W U PACKAGE/ORDER I FOR ATIO
TOP VIEW C2+ C1+ CPO ILED ISET 1 2 3 4 5 11 10 C1– 9 GND 8 C2– 7 VIN 6 EN
VIN to GND ............................................... –0.3V to 5.5V CPO to GND ............................................. –0.3V to 5.5V EN ................................................... –0.3V to VIN + 0.3V ICPO, IILED (Note 2) ........................................... 1000mA CPO Short-Circuit Duration ............................ Indefinite Storage Temperature Range ................. –65°C to 125°C Operating Temperature Range (Note 3) .. –40°C to 85°C
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, CIN = C1 = C2 = 2.2µF, CCPO = 4.7µF.
PARAMETER Input Power Supply VIN Operating Voltage IVIN Operating Current ICPO = 0mA, 1x Mode ICPO = 0mA, 1.5x ICPO = 0mA, 2x Mode EN = LOW ILED = 200mA to 600mA Mode Switch Threshold, ILED = 200mA EN to LED Current On ICPO = 0mA ICPO = 0mA ICPO = 0mA VIN = 3.4V, VCPO < 4.6V, C1 = C2 = 2.2µF VIN = 3.2V, VCPO < 5.1V, C1 = C2 = 2.2µF
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ELECTRICAL CHARACTERISTICS
IVIN Shutdown Current LED Current LED Current Ratio (ILED/ISET) ILED Dropout Voltage Mode Switching Delay (LED Warmup Time) LED Current On Time Charge Pump (CPO) 1x Mode Output Voltage 1.5x Mode Output Voltage 2x Mode Output Voltage 1x Mode Output Impedance 1.5x Mode Output Impedance 2x Mode Output Impedance CLK Frequency EN High Level Input Voltage (VIH) Low Level Input Voltage (VIL) Input Current (IIH) Input Current (IIL)
2
U
W W
W
ORDER PART NUMBER LTC3215EDD DD PART MARKING LBPX
DD PACKAGE 10-LEAD (3mm × 3mm) PLASTIC DFN
TJMAX = 125°C, θJA = 43°C/W EXPOSED PIN (PIN 11) IS GND MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
CONDITIONS
MIN 2.9
TYP
MAX 4.4
UNITS V µA mA mA
300 7 9.2 2.5 3139 3270 120 2.5 130 VIN 4.6 5.1 0.25 1.5 1.7 0.6 1.4 0.4 –1 –1 1 1 0.9 1.2 7 3400
µA mA/mA mV ms µs V V V Ω Ω Ω MHz V V µA µA
3215f
LTC3215
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 3.6V, CIN = C1 = C2 = 2.2µF, CCPO = 4.7µF.
PARAMETER ISET VISET IISET Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Based on long-term current density limitations. Assumes an operating duty cycle of ≤ 10% under absolute maximum conditions for durations less than 10 seconds. Max current for continuous operation is 350mA. ISET = 50µA
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ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN 1.195
TYP 1.22
MAX 1.245 225
UNITS V µA
Note 3: The LTC3215E is guaranteed to meet performance spec.