LTC3215
700mA Low Noise High
Current LED Charge Pump
FEATURES
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DESCRIPTION
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, 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. LED current is pro-
grammed with an external resistor. The LED is disconnected
from V
IN
during shutdown.
An ultralow dropout current source maintains accurate
LED current at very low I
LED
voltages. Automatic mode
switching optimizes efficiency by monitoring the voltage
across the LED current source and switching modes only
when I
LED
dropout is detected. The LTC3215 is available
in a low profile 3mm
×
3mm 10-Lead DFN package.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6411531.
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High Efficiency Operation: 1x, 1.5x or 2x Boost
Modes with Automatic Mode Switching
Ultralow Dropout I
LED
Current Control
Output Current up to 700mA
Low Noise Constant Frequency Operation*
Wide V
IN
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
APPLICATIONS
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LED Torch/Camera Light Supply for Cell Phones,
PDAs and Digital Cameras
General Lighting and/or Flash/Strobe Applications
TYPICAL APPLICATION
C1
2.2µF
C2
2.2µF
Efficiency vs V
IN
100
90
EFFICIENCY (P
LED
/P
IN
) (%)
I
LED
= 200mA
C1
+
2.9V TO 4.4V
C
IN
2.2µF
V
IN
C1
–
C2
+
C2
–
CPO
LED1
I
LED
200mA
C
CPO
4.7µF
80
70
60
50
40
30
20
10
0
LED = AOT2015
V
F
= 3V TYP AT 200mA
2.8 3.0
3.2
LTC3215
I
LED
DISABLE ENABLE
EN
I
SET
20k
1%
3215 TA01a
LED1: AOT2015
3.4 3.6 3.8
V
IN
(V)
4.0
4.2
4.4
3215 TA01b
3215fc
1
LTC3215
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
C2
+
C1
+
CPO
I
LED
I
SET
1
2
3
4
5
11
10 C1
–
9 GND
8 C2
–
7 V
IN
6 EN
V
IN
to GND ............................................... –0.3V to 5.5V
CPO to GND ............................................. –0.3V to 5.5V
EN ................................................... –0.3V to V
IN
+ 0.3V
I
CPO
, I
ILED
(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
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3215EDD#PBF
TAPE AND REEL
LTC3215EDD#TRPBF
PART MARKING
LBPX
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, C
IN
= C1 = C2 = 2.2µF, C
CPO
= 4.7µF.
PARAMETER
Input Power Supply
V
IN
Operating Voltage
I
VIN
Operating Current
I
VIN
Shutdown Current
LED Current
LED Current Ratio (I
LED
/I
SET
)
I
LED
Dropout Voltage
Mode Switching Delay (LED Warm-Up 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
V
IN
= 3.4V, V
CPO
< 4.6V
V
IN
= 3.2V, V
CPO
< 5.1V
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
2.9
TYP
MAX
4.4
UNITS
V
µA
mA
mA
I
CPO
= 0mA, 1x Mode
I
CPO
= 0mA, 1.5x
I
CPO
= 0mA, 2x Mode
EN = LOW
I
LED
= 200mA to 600mA
Mode Switch Threshold, I
LED
= 200mA
EN to LED Current On
I
CPO
= 0mA
I
CPO
= 0mA
I
CPO
= 0mA
●
300
7
9.2
2.5
3139
3270
120
2.5
130
V
IN
4.6
5.1
0.25
1.5
1.7
0.6
0.9
1.2
7
3400
µA
mA/mA
mV
ms
µs
V
V
V
Ω
Ω
Ω
MHz
3215fc
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LTC3215
ELECTRICAL CHARACTERISTICS
PARAMETER
CPO Short Circuit Detection
Threshold Voltage
Test Current
EN
High Level Input Voltage (V
IH
)
Low Level Input Voltage (V
IL
)
Input Current (I
IH
)
Input Current (I
IL
)
I
SET
V
ISET
I
ISET
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. Max current for continuous operation is
350mA.
I
SET
= 50µA
●
●
●
●
●
●
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, C
IN
= C1 = C2 = 2.2µF, C
CPO
= 4.7µF.
CONDITIONS
EN = High
EN = Low, V
CPO
= 0V
●
●
MIN
0.5
10
1.4
TYP
MAX
1.5
30
UNITS
V
mA
V
0.4
–1
–1
1.195
1.22
1
1
1.245
225
V
µA
µA
V
µA
Note 3:
The LTC3215E 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
I
LED
Dropout Voltage
vs LED Current
0.8
0.7
I
LED
PIN CURRENT (mA)
DROPOUT VOLTAGE (V)
0.6
0.5
0.4
0.3
0.2
0.1
0
0
400
600
200
LED CURRENT (mA)
800
3216 G01
(T
A
= 25°C unless otherwise specified)
V
IN
= 3.6V
600
500
400
300
200
100
0
I
LED
Pin Current
vs I
LED
Pin Voltage
1000
I
LED
= 500mA
800
400mA
300mA
200mA
100mA
I
LED
(mA)
600
400
200
0
I
LED
vs R
SET
0
0.2
0.4
0.6
0.8
I
LED
PIN VOLTAGE (V)
1.0
3216 G02
0
5
10
15 20 25
R
SET
(kΩ)
30
35
40
1573 G03
3215fc
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LTC3215
TYPICAL PERFORMANCE CHARACTERISTICS
1x Mode Charge Pump Open-
Loop Output Resistance vs
Temperature
0.31
0.29
OUTPUT RESISTANCE (Ω)
0.27
0.25
0.23
0.21
0.19
0.17
0.15
–40
–15
35
TEMPERATURE (°C)
10
60
85
3216 G04
(T
A
= 25°C unless otherwise specified)
2x Mode Charge Pump
Open-Loop Output Resistance
(2V
IN
– V
CPO
)/I
CPO
vs Temperature
I
CPO
= 200mA
V
IN
= 3.3V
V
IN
= 3.6V
V
IN
= 3.9V
OUTPUT RESISTANCE (Ω)
1.8
1.6
1.5x Mode Charge Pump
Open-Loop Output Resistance (1.5V-
IN
– V
CPO
)/I
CPO
vs Temperature
2.0
1.8
OUTPUT RESISTANCE (Ω)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
1.4
1.2
1.0
0.8
0.6
0.4
0.2
V
IN
= 3V
V
CPO
= 4.2V
C
IN
= C1 = C2 = 2.2µF
C
CPO
= 4.7µF
–15
35
10
TEMPERATURE (°C)
60
85
3216 G05
0
–40
0
–40
V
IN
= 3V
V
CPO
= 4.8V
C
IN
= C1 = C2 = 2.2µF
C
CPO
= 4.7µF
–15
35
10
TEMPERATURE (°C)
60
85
3216 G06
Input Shutdown Current
vs Input Voltage
4.0
INPUT SHUTDOWN CURRENT (µA)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
2.9
3.1 3.3
3.5 3.7 3.9 4.1
INPUT VOLTAGE (V)
4.3
4.5
T
A
= 85°C
T
A
= –40°C
T
A
= 25°C
FREQUENCY (kHz)
930
920
Oscillator Frequency
vs Supply Voltage
100
90
Efficiency vs V
IN
200mA
400mA
600mA
T
A
= 25°C
T
A
= –40°C
T
A
= 85°C
EFFICIENCY (P
LED
/P
IN
) (%)
910
900
890
880
870
860
850
840
2.9
80
70
60
50
40
30
20
3.1 3.3 3.5 3.7 3.9 4.1
SUPPLY VOLTAGE (V)
4.3
4.5
10 LED = LXCL-PWF1 LUMILEDS
V
F
= 3V TYP AT 200mA
0
2.8 3.0 3.2 3.4 3.6 3.8
V
IN
(V)
4.0
4.2
4.4
3216 G07
3216 G08
3216 G09
1.5x Mode CPO Output Ripple
2x Mode CPO Output Ripple
V
CPO
50mV/DIV
A/C COUPLED
V
CPO
20mV/DIV
A/C COUPLED
V
IN
= 3.6V
I
CPO
= 200mA
500ns/DIV
3216 G10
V
IN
= 3.6V
I
CPO
= 400mA
500ns/DIV
3216 G11
3215fc
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LTC3215
TYPICAL PERFORMANCE CHARACTERISTICS
Charge Pump Mode Switching
and Input Current (I
LED
= 400mA)
100
V
CPO
1V/DIV
I
VIN
500mA/
DIV
EN2
5V/DIV
V
IN
= 3V
1ms/DIV
3215 G12
(T
A
= 25°C unless otherwise specified)
I
SET
/I
LED
Current Ratio
vs I
LED
Current
3400
3350
CURRENT RATIO
3300
3250
85°C
3200
3150
3100
Efficiency vs V
IN
90
EFFICIENCY (P
LED
/P
IN
) (%)
80
70
60
50
40
30
20
10
0
100mA
200mA
400mA
AOT2015
V
F
= 3V TYP AT 200mA
2.8 3.0
3.2
3.4 3.6 3.8
V
IN
(V)
4.0
4.2
4.4
25°C
–40°C
0
600
200
400
I
LED
CURRENT (mA)
800
3215 G14
3215 G13
PIN FUNCTIONS
C2
+
, C1
+
, C2
–
, C1
–
(Pins 1, 2, 8, 10):
Charge Pump
Flying Capacitor Pins. A 2.2µF X5R or X7R ceramic ca-
pacitor should be connected from C1
+
to C1
–
and from
C2
+
to C2
–
.
CPO (Pin 3):
Output. CPO is the output of the Charge
Pump. This pin may be enabled or disabled using the EN
input. A 4.7µF X5R or X7R ceramic capacitor is required
from CPO to GND.
I
LED
(Pin 4):
Output. I
LED
is the LED current source
output. The LED is connected between CPO (anode) and
I
LED
(cathode). The current into the I
LED
pin is set by the
programming resistor connected from I
SET
to GND.
I
SET
(Pin 5):
LED Current Programming Resistor Pin. The
I
SET
pin will servo to 1.22V. A resistor connected between
this pin and GND is used to set the LED current level. Con-
necting a resistor of 2k or less will cause the LTC3215 to
enter overcurrent shutdown mode.
EN (Pin 6):
Input. The EN is used to enable the part or put
it into shutdown mode.
V
IN
(Pin 7):
Power. Supply voltage for the LTC3215. V
IN
should be bypassed with a 2.2µF or greater low impedance
ceramic capacitor to GND.
GND (Pin 9):
Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
EXPOSED PAD (Pin 11):
Control Signal Ground. This pad
must be soldered to a low impedance ground plane for
optimum thermal and electrical performance.
3215fc
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