LTC3214
500mA Camera
LED Charge Pump
FEATURES
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DESCRIPTION
The LTC
®
3214 is a low noise, high current charge pump
DC/DC converter capable of driving high current LEDs at
up to 500mA from a 2.9V to 4.5V input. Low external parts
count (two flying capacitors, one programming resistor and
two bypass capacitors at V
IN
and CPO) make the LTC3214
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.
Output current level is programmed by an external resistor.
LED current is regulated using an internal 110mΩ 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
×
3mm 10-lead
DFN package.
L,
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.
Low Noise Constant Frequency Operation
High Efficiency: Up to 94%
Multi-Mode Operation: 1x, 1.5x or 2x Boost Modes
Automatic Mode Switching
High Output Current: Up to 500mA
Tiny Application Circuit (3mm
×
3mm DFN Package,
All Components <1mm High)
Automatic Soft-Start
Output Disconnect
Open, Shorted LED Protection
No Inductors
Internal 110mΩ LED Current Sense Resistor
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
Efficiency vs V
IN
C1
2.2μF
C2
2.2μF
EFFICIENCY (P
LED
/P
IN
) (%)
100
90
80
70
60
50
40
30
20
10
0
3214 TA01a
100mA 200mA
300mA
C1
2.9V TO 4.5V
C
IN
2.2μF
+
C1
–
C2
+
C2
–
CPO
LED
C
CPO
4.7μF
V
IN
LTC3214
50mA
I
LED
DISABLE ENABLE
EN
I
SET
R
SET
0.11Ω
I
LED
UP TO 500mA
LED = AOT2015
V
F
= 2.9V TYP AT 100mA
2.9 3.1
3.3
3.5 3.7 3.9
V
IN
(V)
4.1
4.3
4.5
LED: AOT2015
3214 TA01b
3214fb
1
LTC3214
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) ...............................................600mA
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
LTC3214EDD#PBF
TAPE AND REEL
LTC3214EDD#TRPBF
PART MARKING
LBVQ
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/
ELECTRICAL CHARACTERISTICS
PARAMETER
Input Power Supply
V
IN
Operating Voltage
I
VIN
Operating Current
CONDITIONS
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
,
.
MIN
l
TYP
MAX
4.5
UNITS
V
μA
mA
mA
2.9
980
4.8
6.7
2.5
2715
2950
40
2.5
100
5
0.70
3.2
3.5
I
CPO
= 0mA, 1x Mode
I
CPO
= 0mA, 1.5x
I
CPO
= 0mA, 2x Mode
EN = LOW
I
LED
= 150mA to 500mA
Mode Switch Threshold, ILED = 200mA
EN to LED Current On
I
VIN
Shutdown Current
LED Current
LED Current Ratio (I
LED
/I
SET
)
I
LED
Dropout Voltage (V
ILED
)
Mode Switching Delay (LED Warm-Up Time)
LED Current On Time
Charge Pump (CPO)
Charge Pump Output Clamp Voltage
1x Mode Output Impedance
1.5x Mode Output Impedance
2x Mode Output Impedance
CLK Frequency
CPO Short-Circuit Detection
Threshold Voltage
Test Current
7.5
3190
μA
mA/mA
mV
ms
μs
V
Ω
Ω
Ω
V
IN
= 3V
EN = High
EN = Low, V
CPO
= 0V
l
l
l
0.6
0.5
12
0.9
1.2
1.5
66
MHz
V
mA
3214fb
2
LTC3214
ELECTRICAL CHARACTERISTI CS
PARAMETER
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
300mA.
I
SET
= 50μA
l
l
l
l
l
l
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
MIN
1.4
0.4
14.4
–1
1.18
1.21
20
1
1.24
184
TYP
MAX
UNITS
V
V
μA
μA
V
μA
V
EN
= 3.6V
Note 3:
The LTC3214E 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 PERFORMANCE CHARACTERISTICS
(T
A
= 25°C unless otherwise specified)
I
LED
Dropout Voltage vs
LED Current
0.12
0.10
DROPOUT VOLTAGE (V)
0.08
I
LED
(mA)
0.06
0.04
0.02
0
600
500
OUTPUT RESISTANCE (Ω)
400
300
200
100
0
0
100
200
300
400
LED CURRENT (mA)
500
3216 G01
I
LED
vs R
SET
1.0
0.9
1x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
I
CPO
= 100mA
V
IN
= 2.9V
0.8
0.7
0.6
0.5
0.4
–40
V
IN
= 3.6V
V
IN
= 4.5V
0
50
100 150 200 250 300 350 400
R
SET
(kΩ)
1573 G02
–15
10
35
TEMPERATURE (°C)
60
85
3216 G03
3214fb
3
LTC3214
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C unless otherwise specified)
2x Mode Charge Pump
Open-Loop Output Resistance
(2V
IN
– V
CPO
)/I
CPO
vs Temperature
5
INPUT SHUTDOWN CURRENT (μA)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
60
85
3216 G05
Input Shutdown Current
vs Input Voltage
910
T
A
= –40°C
T
A
= 85°C
FREQUENCY (kHz)
T
A
= 25°C
900
Oscillator Frequency
vs Supply Voltage
OUTPUT RESISTANCE (Ω)
4
T
A
= –40°C
890
880
870
860
850
840
830
T
A
= 25°C
T
A
= 85°C
3
2
1
0
–40
V
IN
= 3.6V
C
IN
= C1 = C2 = 2.2μF
C
CPO
= 4.7μF
–15
35
10
TEMPERATURE (°C)
0
2.9
3.1 3.3
3.5 3.7 3.9 4.1
INPUT VOLTAGE (V)
4.3
4.5
2.9
3.1 3.3 3.5 3.7 3.9 4.1
SUPPLY VOLTAGE (V)
4.3
4.5
3214 G06
3214 G07
Efficiency vs V
IN
100
90
EFFICIENCY (P
LED
/P
IN
) (%)
80
CURRENT RATIO
70
60
50
40
30
20
10
0
LED = AOT2015
V
F
= 2.9V TYP AT 100mA
2.9 3.1
3.3
3.5 3.7 3.9
V
IN
(V)
4.1
4.3
4.5
50mA
100mA 200mA
300mA
3200
3100
3000
3300
I
SET
/I
LED
Current Ratio
vs I
LED
Current
600
500
I
LED
Current vs Input Voltage
7.15k
25°C
85°C
–40°C
2900
2800
2700
0
100
400
I
LED
(mA)
300
200
100
0
2.9
3.1 3.3
3.5
36.6k
72.2k
3.7 3.9
V
IN
(V)
4.1
4.3
4.5
11.8k
17.4k
400
200
300
I
LED
CURRENT (mA)
500
3214 G09
3215 G08
3214 G10
1.5x Mode CPO Output Ripple
2x Mode CPO Output Ripple
V
CPO
50mV/DIV
V
CPO
50mV/DIV
A/C COUPLED
V
IN
= 3.6V
I
CPO
= 200mA
500ns/DIV
3214 G11
V
IN
= 3.6V
I
CPO
= 400mA
500ns/DIV
3214 G12
3214fb
4
LTC3214
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):
Input. I
LED
is the LED current sense pin. The
LED is connected between CPO (anode) and I
LED
(cathode).
The current into the I
LED
pin is set by a resistor connected
to the I
SET
pin and regulated internally.
I
SET
(Pin 5):
LED Current Programming Resistor Pin. A
resistor connected between this pin and GND is used to
set the LED current level.
EN (Pin 6):
Input. The EN pin is used to enable the part
and bring it into shutdown mode. An internal 250k resistor
pulls this pin to GND when left floating.
V
IN
(Pin 7):
Power. Supply voltage for the LTC3214. V
IN
should be bypassed with a 2.2μF to 4.7μF 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 DIAGRAM
2
C1
+
10
C1
–
1
C2
+
8
C2
–
CPO
3
OSCILLATOR
–
VOLTAGE
CLAMP
+
MODE
CONTROL
7
6
V
IN
EN
250k
GND
9
5
I
SET
GND
11
3214 BD
V
REF
V
IN
I
LED
4
CURRENT
SOURCE
CONTROL
CONTROL
LOGIC
58Ω
0.11Ω
3214fb
5
MCU
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