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 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
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.
*Protected by U.S. Patent 6411531.
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
I
LED
= 200mA
C1
2.9V TO 4.4V
C
IN
2.2µF
EFFICIENCY (P
LED
/P
IN
) (%)
+
C1
–
C2
+
C2
–
CPO
LED1
C
CPO
4.7µF
80
70
60
50
40
30
20
10
V
IN
LTC3215
I
LED
DISABLE ENABLE
EN
I
SET
20k
1%
3215 TA01a
I
LED
200mA
LED = AOT2015 HPW 1751B
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
0
LED1: AOT2015 HPW 1751B
U
Efficiency vs V
IN
3215 TA01b
U
U
3215f
1
LTC3215
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
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
ORDER PART
NUMBER
LTC3215EDD
DD PART
MARKING
LBPX
DD PACKAGE
10-LEAD (3mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 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.
The
●
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
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
V
IN
= 3.4V, V
CPO
< 4.6V, C1 = C2 = 2.2µF
V
IN
= 3.2V, V
CPO
< 5.1V, C1 = C2 = 2.2µF
●
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
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
V
IN
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
I
VIN
Shutdown Current
LED Current
LED Current Ratio (I
LED
/I
SET
)
I
LED
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 (V
IH
)
Low Level Input Voltage (V
IL
)
Input Current (I
IH
)
Input Current (I
IL
)
mA/mA
mV
ms
µs
V
V
V
Ω
Ω
Ω
MHz
V
V
µA
µA
2
U
µA
3215f
W
U
U
W W
W
LTC3215
The
●
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
I
SET
V
ISET
I
ISET
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.
I
SET
= 50µA
●
●
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 specifications
from 0°C to 70°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 PERFOR A CE CHARACTERISTICS
I
LED
Dropout Voltage
vs LED Current
0.8
0.7
V
IN
= 3.6V
600
500
I
LED
PIN CURRENT (mA)
DROPOUT VOLTAGE (V)
0.6
0.5
0.4
0.3
0.2
0.1
0
0
200
400
600
LED CURRENT (mA)
800
3216 G01
300
200
100
0
300mA
200mA
100mA
I
LED
(mA)
1x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
0.31
0.29
I
CPO
= 200mA
V
IN
= 3.3V
V
IN
= 3.6V
V
IN
= 3.9V
1.8
1.6
OUTPUT RESISTANCE (Ω)
0.27
0.25
0.23
0.21
0.19
0.17
0.15
–40
OUTPUT RESISTANCE (Ω)
OUTPUT RESISTANCE (Ω)
–15
35
TEMPERATURE (°C)
10
U W
60
85
3216 G07
(T
A
= 25°C unless otherwise specified)
I
LED
Pin Current
vs I
LED
Pin Voltage
1000
I
LED
= 500mA
800
400mA
600
I
LED
vs R
SET
400
400
200
0
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 G06
1.5x Mode Charge Pump
Open-Loop Output Resistance
(1.5V
IN
– V
CPO
)/I
CPO
vs Temperature
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
60
85
3216 G05
2x Mode Charge Pump
Open-Loop Output Resistance
(2V
IN
– V
CPO
)/I
CPO
vs Temperature
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)
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
3215f
3
LTC3215
TYPICAL PERFOR A CE CHARACTERISTICS
Input Shutdown Current
vs Input Voltage
4.0
930
920
T
A
= 25°C
T
A
= –40°C
T
A
= 85°C
INPUT SHUTDOWN CURRENT (µA)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
2.9
3.5 3.7 3.9 4.1
INPUT VOLTAGE (V)
T
A
= 85°C
T
A
= –40°C
T
A
= 25°C
EFFICIENCY (P
LED
/P
IN
) (%)
FREQUENCY (kHz)
3.1
3.3
Efficiency vs V
IN
100
90
3400
3350
EFFICIENCY (P
LED
/P
IN
) (%)
80
CURRENT RATIO
70
60
50
40
30
20
10
0
100mA
200mA
400mA
AOT2015 HPW 1751B
V
F
= 3V TYP AT 100mA
2.8 3.0
3.2
3.4 3.6 3.8
V
IN
(V)
4.0
4.2
4.4
1.5x Mode CPO Output Ripple
V
CPO
50mV/DIV
A/C COUPLED
V
IN
= 3.6V
I
CPO
= 200mA
500ns/DIV
4
U W
4.3
3216 G04
(T
A
= 25°C unless otherwise specified)
Oscillator Frequency
vs Supply Voltage
100
90
80
70
60
50
40
30
20
Efficiency vs V
IN
910
900
890
880
870
860
850
840
4.5
2.9
3.1
200mA
400mA
600mA
3.3 3.5 3.7 3.9 4.1
SUPPLY VOLTAGE (V)
4.3
4.5
10 LED = LXCL-PWF1 LUMILED
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 G03
3216 G11
I
SET
/I
LED
Current Ratio
vs I
LED
Current
3300
25°C
3250
85°C
3200
3150
3100
0
–40°C
600
200
400
I
LED
CURRENT (mA)
800
3215 G16
3215 G15
2x Mode CPO Output Ripple
Charge Pump Mode Switching
and Input Current (I
LED
= 400mA)
V
CPO
1V/DIV
V
CPO
20mV/DIV
A/C COUPLED
I
VIN
500mA/
DIV
EN2
5V/DIV
3216 G12
V
IN
= 3.6V
I
CPO
= 400mA
500ns/DIV
3216 G13
V
IN
= 3V
1ms/DIV
3215 G14
3215f
LTC3215
PI FU CTIO S
C2
+
, C1
+
, C2
–
, C1
–
(Pins 1, 2, 8, 10):
Charge Pump
Flying Capacitor Pins. A 2.2µF 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 4.7µF 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.
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 2.2µF 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.
BLOCK DIAGRA
7
6
V
IN
EN
W
U
U
U
2
C1
+
10
C1
–
1
C2
+
8
C2
–
CPO
3
OSCILLATOR
1X MODE: CPO = V
IN
1.5X MODE: CPO = 4.6V
2X MODE: CPO = 5.1V
–
+
MODE
CONTROL
V
REF
DROPOUT
DETECTOR
I
LED
4
CONTROL
LOGIC
GND
9
CURRENT
SOURCE
CONTROL
I
SET
5
GND
11
3215 BD
3215f
5
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