LTC3215
1
3215f
TYPICAL APPLICATIO
U
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
LED Torch/Camera Light Supply for Cell Phones,
PDAs and Digital Cameras
General Lighting and/or Flash/Strobe Applications
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: 2.5A
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
700mA Low Noise High
Current LED Charge Pump
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 capaci-
tors, one programming resistor and two bypass capaci-
tors) 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 discon-
nected 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Efficiency vs V
IN
C1
2.2F
C2
2.2F
C
IN
2.2F
C
CPO
4.7F
I
LED
200mA
LED1
I
LED
V
IN
2.9V TO 4.4V
EN
DISABLE ENABLE
LTC3215
C1
+
C1
C2
+
C2
I
SET
3215 TA01a
LED1: AOT2015 HPW 1751B
CPO
20k
1%
V
IN
(V)
2.8
EFFICIENCY (P
LED
/P
IN
) (%)
100
90
80
70
60
50
40
30
20
10
0
3.2
3.6
3.8
3215 TA01b
3.0
3.4
4.0
4.2
4.4
LED = AOT2015 HPW 1751B
V
F
= 3V TYP AT 200mA
I
LED
= 200mA
*Protected by U.S. Patent 6411531.
LTC3215
2
3215f
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 ................. 65C to 125C
Operating Temperature Range (Note 3) .. 40C to 85C
ORDER PART
NUMBER
T
JMAX
= 125C,
JA
= 43C/W
EXPOSED PIN (PIN 11) IS GND
MUST BE SOLDERED TO PCB
LTC3215EDD
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
(Note 1)
ELECTRICAL CHARACTERISTICS
The
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25C. V
IN
= 3.6V, C
IN
= C1 = C2 = 2.2F, C
CPO
= 4.7F.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DD PART
MARKING
LBPX
TOP VIEW
11
DD PACKAGE
10-LEAD (3mm 3mm) PLASTIC DFN
10
9
6
7
8
4
5
3
2
1
C1
GND
C2
V
IN
EN
C2
+
C1
+
CPO
I
LED
I
SET
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Input Power Supply
V
IN
Operating Voltage
2.9
4.4
V
I
VIN
Operating Current
I
CPO
= 0mA, 1x Mode
300
A
I
CPO
= 0mA, 1.5x
7
mA
I
CPO
= 0mA, 2x Mode
9.2
mA
I
VIN
Shutdown Current
EN = LOW
2.5
7
A
LED Current
LED Current Ratio (I
LED
/I
SET
)
I
LED
= 200mA to 600mA
3139
3270
3400
mA/mA
I
LED
Dropout Voltage
Mode Switch Threshold, I
LED
= 200mA
120
mV
Mode Switching Delay (LED Warmup Time)
2.5
ms
LED Current On Time
EN to LED Current On
130
s
Charge Pump (CPO)
1x Mode Output Voltage
I
CPO
= 0mA
V
IN
V
1.5x Mode Output Voltage
I
CPO
= 0mA
4.6
V
2x Mode Output Voltage
I
CPO
= 0mA
5.1
V
1x Mode Output Impedance
0.25
1.5x Mode Output Impedance
V
IN
= 3.4V, V
CPO
< 4.6V, C1 = C2 = 2.2F
1.5
2x Mode Output Impedance
V
IN
= 3.2V, V
CPO
< 5.1V, C1 = C2 = 2.2F
1.7
CLK Frequency
0.6
0.9
1.2
MHz
EN
High Level Input Voltage (V
IH
)
1.4
V
Low Level Input Voltage (V
IL
)
0.4
V
Input Current (I
IH
)
1
1
A
Input Current (I
IL
)
1
1
A
LTC3215
3
3215f
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.
Note 3: The LTC3215E is guaranteed to meet performance specifications
from 0C to 70C. Specifications over the 40C to 85C ambient
operating temperature range are assured by design, characterization and
correlation with statistical process controls.
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
I
LED
Dropout Voltage
vs LED Current
I
LED
Pin Current
vs I
LED
Pin Voltage
I
LED
vs R
SET
LED CURRENT (mA)
0
200
DROPOUT VOLTAGE (V)
400
800
600
3216 G01
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
I
LED
PIN VOLTAGE (V)
0
I
LED
PIN CURRENT (mA)
600
500
400
300
200
100
0
0.2
0.4
0.6
0.8
3216 G02
1.0
TEMPERATURE (C)
40
OUTPUT RESISTANCE (
)
10
60
85
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
3216 G05
15
35
40
10
60
85
15
35
TEMPERATURE (C)
OUTPUT RESISTANCE (
)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
3216 G06
I
LED
= 500mA
400mA
300mA
200mA
100mA
V
IN
= 3V
V
CPO
= 4.2V
C
IN
= C1 = C2 = 2.2F
C
CPO
= 4.7F
V
IN
= 3V
V
CPO
= 4.8V
C
IN
= C1 = C2 = 2.2F
C
CPO
= 4.7F
TEMPERATURE (C)
40
OUTPUT RESISTANCE (
)
35
85
3216 G07
15
10
60
0.31
0.29
0.27
0.25
0.23
0.21
0.19
0.17
0.15
I
CPO
= 200mA
V
IN
= 3.6V
V
IN
= 3.3V
V
IN
= 3.9V
V
IN
= 3.6V
R
SET
(k)
I
LED
(mA)
1573 G06
1000
800
600
400
200
0
0
10
20
25
5
15
30
35
40
1.5x Mode Charge Pump
Open-Loop Output Resistance
(1.5V
IN
V
CPO
)/I
CPO
vs Temperature
2x Mode Charge Pump
Open-Loop Output Resistance
(2V
IN
V
CPO
)/I
CPO
vs Temperature
1x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(T
A
= 25C unless otherwise specified)
ELECTRICAL CHARACTERISTICS
The
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25C. V
IN
= 3.6V, C
IN
= C1 = C2 = 2.2F, C
CPO
= 4.7F.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
SET
V
ISET
I
SET
= 50A
1.195
1.22
1.245
V
I
ISET
225
A
LTC3215
4
3215f
V
IN
(V)
2.8
EFFICIENCY (P
LED
/P
IN
) (%)
100
90
80
70
60
50
40
30
20
10
0
3.2
3.6
3.8
3216 G11
3.0
3.4
4.0
4.2
4.4
LED = LXCL-PWF1 LUMILED
V
F
= 3V TYP AT 200mA
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
INPUT SHUTDOWN CURRENT (
A)
3216 G04
INPUT VOLTAGE (V)
2.9
4.5
3.3
3.7
4.1
3.1
3.5
3.9
4.3
T
A
= 85C
T
A
= 40C
T
A
= 25C
FREQUENCY (kHz)
930
920
910
900
890
880
870
860
850
840
3216 G03
SUPPLY VOLTAGE (V)
2.9
4.5
3.3
3.7
4.1
3.1
3.5
3.9
4.3
T
A
= 85C
T
A
= 40C
T
A
= 25C
600mA
400mA
200mA
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Efficiency vs V
IN
1.5x Mode CPO Output Ripple
2x Mode CPO Output Ripple
Input Shutdown Current
vs Input Voltage
Oscillator Frequency
vs Supply Voltage
Charge Pump Mode Switching
and Input Current (I
LED
= 400mA)
V
CPO
1V/DIV
I
VIN
500mA/
DIV
V
IN
= 3V
1ms/DIV
3215 G14
EN2
5V/DIV
3216 G12
V
CPO
50mV/DIV
A/C COUPLED
500ns/DIV
V
IN
= 3.6V
I
CPO
= 200mA
3216 G13
V
CPO
20mV/DIV
A/C COUPLED
500ns/DIV
V
IN
= 3.6V
I
CPO
= 400mA
Efficiency vs V
IN
I
SET
/I
LED
Current Ratio
vs I
LED
Current
V
IN
(V)
2.8
EFFICIENCY (P
LED
/P
IN
) (%)
100
90
80
70
60
50
40
30
20
10
0
3.2
3.6
3.8
3215 G15
3.0
3.4
4.0
4.2
4.4
AOT2015 HPW 1751B
V
F
= 3V TYP AT 100mA
100mA
200mA
400mA
I
LED
CURRENT (mA)
0
3100
CURRENT RATIO
3150
3200
3250
40C
25C
85C
3300
200
400
600
800
3215 G16
3350
3400
(T
A
= 25C unless otherwise specified)
LTC3215
5
3215f
U
U
U
PI FU CTIO S
BLOCK DIAGRA
W
2
3
4
11
9
10
5
+
1
8
1X MODE: CPO = V
IN
1.5X MODE: CPO = 4.6V
2X MODE: CPO = 5.1V
V
REF
DROPOUT
DETECTOR
CONTROL
LOGIC
MODE
CONTROL
OSCILLATOR
6
7
GND
CPO
I
LED
GND
I
SET
V
IN
EN
C1
+
C1
C2
+
C2
3215 BD
CURRENT
SOURCE
CONTROL
C2
+
, C1
+
, C2
, C1
(Pins 1, 2, 8, 10): Charge Pump
Flying Capacitor Pins. A 2.2F X5R or X7R ceramic
capacitor 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 4.7F 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.
Connecting 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 2.2F 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.
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