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FEATURES
Charge Pump Provides High Efficiency with
Automatic Mode Switching
Multimode Operation: 1x, 1.5x, 2x
Four Low Dropout LED Outputs
Up to 600mA Total Output Current
Independent Torch and Flash ISET and Enable Pins
Low Noise Constant Frequency Operation*
PWM Brightness Control via the EN2 Pin
Low Shutdown Current: 4µA
Internal Soft-Start Limits Inrush Current During
Start-Up and Mode Switching
Open/Short LED Protection
No Inductors
(3mm x 3mm) 16-Lead QFN Plastic Package
U
APPLICATIO S
Multi-LED Camera Light Supply for Cellphones/
DSCs/PDAs
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Protected by U.S. Patents, including 6411531
LTC3217www.DataSheet4U.com
600mA Low Noise
Multi-LED Camera Light
Charge Pump
DESCRIPTIO
The LTC®3217 is a low noise charge pump DC/DC con-
verter designed to power four high current LEDs. The
LTC3217 requires only four small ceramic capacitors and
two current set resistors to form a complete LED power
supply and current controller.
Built-in soft-start circuitry prevents excessive inrush cur-
rent during start-up and mode changes. High switching
frequency enables the use of small external capacitors.
Independent high and low current settings are programmed
by two external resistors. Shutdown mode and current
output levels are selected via two logic inputs.
The current through the LEDs is programmed via ISET1 and
ISET2. In addition, the brightness can be controlled by
pulse width modulation of the EN2 pin.
The charge pump optimizes efficiency based on the volt-
age across the LED current sources. The part powers up
in 1x mode and will automatically switch to boost mode
whenever any enabled LED current source begins to enter
dropout. The first dropout switches the part into 1.5x
mode and a subsequent dropout switches the part into 2x
mode. The LTC3217 resets to 1x mode whenever the part
is shut down.
The LTC3217 is available in a low profile 16-lead (3mm ×
3mm × 0.75mm) QFN package.
TYPICAL APPLICATIO
C2
2.2µF
C3
2.2µF
VBAT
C1
2.2µF
EN1 (TORCH)
EN2 (FLASH)
C1P C1M C2P C2M
VBAT
CPO
LTC3217
EN1
EN2
ISET1
ISET2
LED1
LED2
LED3
LED4
GND
19.6k
1%
6.49k
1%
C4
2.2µF
AOT-2015HPW-1751B
EN1 EN2
ILED
0 0 0 (SHUTDOWN)
10
25mA/LED
01
75mA/LED
1 1 100mA/LED
3217 TA01
Efficiency vs VBAT
100
90 100mA 200mA
80
400mA
70
60
50
40
30
20
TOTAL OUTPUT CURRENT
10 PLED/PIN
LED = 2015 HPW AOT
0
3 3.2 3.4 3.6 3.8 4 4.2 4.4
VBAT (V)
3217 G09
3217f
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LTC3217
ABSOLUTE AXI U RATI GS
(Note 1)
VBAT, CPO to GND ....................................... –0.3V to 6V
EN1, EN2 .................................... –0.3V to (VBAT + 0.3V)
ICPO (Note 2) ....................................................... 600mA
IILED1-4 (Note 3) .................................................. 150mA
CPO Short-Circuit Duration ............................. Indefinite
Operating Temperature Range (Note 4) ...–40°C to 85°C
Storage Temperature Range ..................–65°C to 125°C
www.DataSheet4U.com
UW U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
16 15 14 13
C1P 1
12 C2M
CPO 2
11 EN2
17
EN1 3
10 ISET2
LED1 4
9 ISET1
5678
UD PACKAGE
16-LEAD (3mm × 3mm) PLASTIC QFN
TJMAX = 125°C, θJA = 68°C/W
EXPOSED PAD (PIN 17) IS GND MUST BE SOLDERED TO PCB
ORDER PART NUMBER QFN PART MARKING
LTC3217EUD
LBTQ
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBAT = 3.6V, C1 = C2 = C3 = C4 = 2.2µF, unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
VBAT Operating Voltage
IVBAT Operating Current
VBAT Shutdown Current
LED 1-4 Current
2.9
4.5
RISET1 = RISET2 = 20k, EN1 = EN2 = High
ICPO = 0mA, 1x Mode
ICPO = 0mA, 1.5x Mode
ICPO = 0mA, 2x Mode
1
4
6
4
V
mA
mA
mA
µA
LED Current Ratio (ILED/ISET1/2)
LED Dropout Voltage
Mode Switching Delay
ILED = 25mA to 100mA
Mode Switch Threshold, ILED = 100mA
EN1 Only
370 400 430 mA/mA
330 mV
2.5 ms
LED Current Matching
Charge Pump (CPO)
Any Two Outputs, ILED = 100mA
1%
1x Mode Output Voltage
1.5x Mode Output Voltage
2x Mode Output Voltage
1x Mode Output Impedance
ICPO = 0mA
ICPO = 0mA
ICPO = 0mA
VBAT
V
4.5 V
5.05 V
0.5
1.5x Mode Output Impedance
2x Mode Output Impedance
CLOCK Frequency
VBAT = 3.4V, VCPO 4.6V (Note 5)
VBAT = 3.2V, VCPO 5.1V (Note 5)
0.6
2.8
3.2
0.85 1.15
MHz
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LTC3217www.DataSheet4U.com
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VBAT = 3.6V, C1 = C2 = C3 = C4 = 2.2µF, unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
EN1, EN2
Low Level Input Voltage (VIL)
High Level Input Voltage (VIH)
Input Current (IIH)
Input Current (IIL)
Minimum PWM On-Time
EN2 Only
1.4
7
–1
50
0.4 V
V
30 µA
1 µA
µs
Maximum PWM Off-Time
EN2 to Remain Enabled, EN1 = Low
1 ms
ISET1, ISET2
VISET1, ISET2
IISET1, ISET2 Current Range
IISET1, ISET2 Short-Circuit Current
ILED1-4 = 12.5mA
1.175
31.25
1.215
800
1.255
375
V
µA
µA
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may become impaired.
Note 2: Based on charge pump 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 300mA.
Note 3: Based on LED current source 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 100mA.
Note 4: The LTC3217E 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.
Note 5: 1.5x mode output impedance is defined as (1.5VBAT – VCPO)/IOUT.
2x mode output impedance is defined as (2VBAT – VCPO)/IOUT.
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted.
LED Dropout Voltage
vs LED Current
400
VBAT = 3.6V
300
200
100
0
10 20 30 40 50 60 70 80 90 100
LED CURRENT (mA)
3217 G01
LED Pin Current
vs LED Pin Voltage
120
VBAT = 3.6V
100
80
60
40
20
0
0 0.2 0.4 0.6 0.8 1.0
LED PIN VOLTAGE (V)
3217 G02
ILED vs RISET
120
100
80
60
40
20
0
0 5 10 15 20 25 30 35 40 45 50
RISET (k)
3217 G03
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LTC3217
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TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted.
1x Mode Switch Resistance
vs Temperature
0.65
ICPO = 200mA
0.60
1.5x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(1.5VBAT – VCPO)/ICPO
3.2
VBAT = 3V
VCPO = 4.2V
3.0 C2 = C3 = C4 = 2.2µF
2x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(2VBAT – VCPO)/ICPO
3.8
VBAT = 3V
VCPO = 4.8V
3.6 C2 = C3 = C4 = 2.2µF
0.55
VBAT = 3.6V
0.50
VBAT = 3.3V
0.45
VBAT = 3.9V
2.8
2.6
2.4
3.4
3.2
3.0
0.40 2.2 2.8
0.35
–40
–15 10 35 60
TEMPERATURE (°C)
85
3217 G04
2.0
–40
–15 10 35 60
TEMPERATURE (°C)
85
3217 G05
2.6
–40
–15 10 35 60
TEMPERATURE (°C)
85
3217 G06
VBAT Shutdown Current
vs VBAT Voltage
7.5
6.5
TA = –40°C
5.5
TA = 85°C
4.5
3.5 TA = 25°C
2.5
1.5
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VBAT VOLTAGE (V)
3217 G07
1.5x Mode CPO Output Ripple
Oscillator Frequency
vs Supply Voltage
980
970
960
950
TA = 25°C
940
TA = –40°C
930
TA = 85°C
920
910
900
890
880
2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5
VBAT SUPPLY VOLTAGE (V)
3217 G08
2x Mode CPO Output Ripple
Efficiency vs VBAT
100
90 100mA 200mA
80
400mA
70
60
50
40
30
20
TOTAL OUTPUT CURRENT
10 PLED/PIN
LED = 2015 HPW AOT
0
3 3.2 3.4 3.6 3.8
VBAT (V)
4
4.2 4.4
3217 G09
Charge Pump Mode Switching
and Input Current to Ground
(400mA Load)
VCPO 1x
1V/DIV NO LOAD 1x
2x
1.5x (5V)
VCPO
50mV/DIV
AC COUPLED
VCPO
20mV/DIV
AC COUPLED
IVBAT
500mA/DIV
0
EN1
5V/DIV
DROPOUT
DROPOUT
VBAT = 3.6V
ICPO = 400mA
CCPO = 2.2µF
500ns/DIV
3217 G10
VBAT = 3.6V
ICPO = 400mA
CCPO = 2.2µF
500ns/DIV
3217 G11
VIN = 3.6V
1ms/DIV
3217 G12
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TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted.
1.5x Mode CPO Voltage
vs Load Current
4.8
C2 = C3 = C4 = 2.2µF
4.6
3.4V
4.4 3.5V
3.6V
4.2
3.3V
4.0
3.2V
3.8
3.6
0
3.1V
VBAT = 3V
100 200 300 400
LOAD CURRENT (mA)
500
3217 G13
2x Mode CPO Voltage
vs Load Current
5.2
C2 = C3 = C4 = 2.2µF
5.1
5.0
3.6V
4.9
4.8
3.3V
4.7
3.2V
4.6
3.1V
4.5
VBAT = 3V
4.4
4.3
4.2
0
100 200 300 400
LOAD CURRENT (mA)
500
3217 G14
PI FU CTIO S
C1P, C2P, C1M, C2M (Pins 1, 16, 14, 12): Charge Pump
Flying Capacitor Pins. A 2.2µF X7R or X5R ceramic capaci-
tor should be connected from C1P to C1M and C2P to C2M.
CPO (Pin 2): Output of the charge pump used to power all
LEDs. This pin is enabled or disabled using the EN1 and
EN2 inputs. A 2.2µF X5R or X7R ceramic capacitor should
be connected to ground.
EN1, EN2 (Pins 3, 11): Inputs. The EN1 and EN2 pins are
used to select which current level is being supplied to the
LEDs, as well as to put the part into shutdown mode. The
truth table for these pins is as follows:
Truth Table
EN1
0
1
0
1
EN2 MODE
0 Shutdown
0 Low Current
1 High Current
1 Low + High Current
EN2 can be used for PWM of the LED currents. For proper
operation, the minimum pulse width should be 50µs and
the maximum low time should be 1ms if EN1 is low. If EN1
is high then the 1ms low time limitation does not apply.
LED1, LED2, LED3, LED4 (Pins 4, 5, 6, 7): LED1 to LED4
are the current source outputs. Each LED is connected in
between CPO (anodes) and LED1 – 4 (cathodes). The
current to each LED output is set via the EN1 and EN2
inputs, and the programming resistors connected from
ISET1 and ISET2 to GND. Any of the four LED outputs can
be disabled by connecting the output directly to CPO.
10µA of current will flow through each directly connected
LED output. For single LED applications, all four LED pins
may be tied together and will accurately share current.
GND2 (Pin 8): Analog Ground. This pin should be
connected directly to a low impedance ground plane.
ISET1/ISET2 (Pins 9, 10): LED Current Programming
Resistor Pins. The ISET1 and ISET2 pins will servo to 1.22V.
Resistors connected between each of these pins and GND
are used to set the high and low LED current levels.
Connecting a resistor 2k or less will cause the LTC3217 to
enter over-current shutdown.
GND1 (Pin 13): Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
VBAT (Pin 15): Supply Voltage. This pin should be
bypassed with a 2.2µF, or greater low ESR ceramic
capacitor.
Exposed Pad (Pin 17): This pad should be connected
directly to a low impedance ground plane for optimal
thermal and electrical performance.
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