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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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ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN to GND ................................................... –0.3V to 6V
CPO to GND ................................................ –0.3V to 6V
ENF, ENT .......................................... –0.3V to VIN + 0.3V
ICPO, IILED (Note 2)...............................................500mA
CPO Short-Circuit Duration.............................. Indefinite
Storage Temperature Range................... –65°C to 125°C
Operating Temperature Range (Note 3) ... –40°C to 85°C
PIN CONFIGURATION
TOP VIEW
CP 1
CPO 2
ILED 3
ENT 4
ISETT 5
10 VIN
9 CM
11 8 GND
7 ENF
6 ISETF
DDB PACKAGE
10-LEAD (3mm × 2mm) PLASTIC DFN
TJMAX = 125°C, θJA = 76°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
LTC3218EDDB#PBF
LTC3218EDDB#TRPBF LCHS
10-Lead (3mm × 2mm) Plastic DFN
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
TEMPERATURE RANGE
–40°C to 85°C
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 3.6V, CIN = CFLY = 2.2µF, CCPO = 4.7µF, ENF = HIGH, unless
otherwise noted.
PARAMETER
Input Power Supply
VIN Operating Voltage
IVIN Operating Current
IVIN Shutdown Current
LED Current
CONDITIONS
ICPO = 0mA, 1x Mode
ICPO = 0mA, 2x Mode
ENF = ENT = LOW, VCPO = 0V
MIN TYP MAX UNITS
2.9
4.5
980
1.7
1.1 3
V
µA
mA
µA
Torch Current Ratio
(ILED/ISET)
Flash Current Ratio
(ILED/ISET)
Flash Current Ratio
(ILED/ISET)
ILED Dropout Voltage (VILED)
Mode Switching Delay (LED Warm-Up Time)
ILED = 50mA
ENT = HIGH, ENF = LOW
ILED = 150mA
ENT = LOW, ENF = HIGH
ILED = 150mA
ENT = ENF = HIGH
Mode Switching Threshold, Δ(VCPO – VILED),
ILED = 100mA
765 850 935
2205 2450 2695
2970 3300 3630
7
0.5
A/A
A/A
A/A
mV
ms
Turn-On Time
Minimum LED Forward Voltage
ENF, ENT to LED Current On
ILED = 50mA
2.2
160
µs
V
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ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 3.6V, CIN = CFLY = 2.2µF, CCPO = 4.7µF, ENF = HIGH, unless
otherwise noted.
PARAMETER
Charge Pump (CPO)
Charge Pump Output Clamp Voltage
1:1 Mode Output Impedance
1:2 Mode Output Impedance
CLK Frequency
ENF, ENT
High Level Input Voltage (VIH)
Low Level Input Voltage (VIL)
Input Current (IIH)
Input Current (IIL)
Flash Timeout
ISETF, ISETT
VISET
IISET
CONDITIONS
VEN = 3.6V
VEN = 0V
ENF = HIGH
ISET = 110µA
ENT = LOW, ENF = HIGH
MIN TYP MAX UNITS
5.3 V
1.3 Ω
7Ω
1 MHz
1.4
0.4
14.4 30
–1
1
2
V
V
µA
µA
s
1.18 1.21 1.24
181
V
µA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
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. Maximum current for continuous
operation is 150mA.
Note 3: The LTC3218E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C ambient
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
ILED Dropout Voltage
vs LED Current
0.009
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0
0 100 200 300 400
LED CURRENT (mA)
3218 G01
ILED vs RSET
450
400
350
TORCH
FLASH (ENT = LOW,
ENF = HIGH)
FLASH (ENT = ENF = HIGH)
300
250
200
150
100
50
0
0 50 100 150 200 250 300 350
RSET (k)
3218 G02
VIN Shutdown Current vs VIN
3.0
T = 25°C
2.5
2.0
T = –40°C
1.5
T = 85°C
1.0
0.5
0
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VIN (V)
3218 G03
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TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
1x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
1.8 ICPO = 50mA
1.6
1.4
VIN = 2.9V
1.2
1.0
VIN = 4.5V
0.8
VIN = 3.6V
0.6
0.4
0.2
0
– 40
–15 10
35
TEMPERATURE (°C)
60 85
3218 G04
Torch Mode ILED/ISET Current Ratio
vs ILED Current
1400
1300
1200
1100
1000
900
800
700
600
500
400
50 60 70 80 90 100 110 120 130 140 150
ILED CURRENT (mA)
3218 G07
2x Mode Charge Pump
Open-Loop Output Resistance
(2VIN – VCPO)/ICPO vs Temperature
10
VIN = 3.6V
9
8
7
6
5
4
3
2
1
0
– 40
–15 10
35
TEMPERATURE (°C)
60 85
3218 G05
Flash ILED/ISET Current Ratio
vs ILED Current
(ENT = LOW, ENF = HIGH)
3500
3300
3100
2900
2700
2500
2300
2100
1900
1700
1500
100
150 200 250 300
ILED CURRENT(mA)
350 400
3218 G08
Oscillator Frequency vs VIN
1100
1080
1060
T = –40°C
1040
1020
1000
T = 25°C
T = 85°C
980
960
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VIN (V)
3218 G06
Flash ILED/ISET Current Ratio
vs ILED Current
(ENT = ENF = HIGH)
4500
4300
4100
3900
3700
3500
3300
3100
2900
2700
2500
100 150 200 250 300 350 400
ILED CURRENT(mA)
3218 G09
Torch Mode ILED Current vs VIN
160
140
RSETT = 7.49k
120
100 RSETT = 10.2k
80
60 RSETT = 20k
40
RSETT = 40.2k
20
0
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VIN (V)
3218 G10
Flash Mode ILED Current vs VIN
(ENT = ENF = HIGH)
450
RSETF = 10.2k
400
350
300
250
RSETF = 20k
200
150
RSETF = 40.2k
100
50
0
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VIN (V)
3218 G11
Flash Mode ILED Current vs VIN
(ENT = LOW, ENF = HIGH)
450
400 RSETF = 7.49k
350
300 RSETF = 10.2k
250
200
RSETF = 20k
150
100 RSETF = 40.2k
50
0
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VIN (V)
3218 G12
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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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