FEATURES
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LTC3217
600mA Low Noise
Multi-LED Camera Light
Charge Pumps
DESCRIPTION
The LTC
®
3217 is a low noise charge pump DC/DC converter
designed to power four high current LEDs. The LTC3217
requires only four small ceramic capacitors and two cur-
rent 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 I
SET1
and I
SET2
. 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.
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 I
SET
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
APPLICATIONS
n
Multi-LED Camera Light Supply for Cellphones/
DSCs/PDAs
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.
TYPICAL APPLICATION
C2
2.2μF
C3
2.2μF
100
C1P
V
BAT
C1
2.2μF
V
BAT
LTC3217
LED1
LED2
EN1 (TORCH)
EN2 (FLASH)
EN1
EN2
I
SET1
19.6k
1%
I
SET2
LED3
LED4
GND
EN1
0
1
0
1
EN2
0
0
1
1
I
LED
0 (SHUTDOWN)
25mA/LED
75mA/LED
100mA/LED
C1M C2P
C2M
C4
2.2μF
EFFICIENCY (P
LED
/PIN) (%)
CPO
AOT-2015HPW-1751B
90
80
70
60
50
40
30
20
10
0
3
3217 TA01
Efficiency vs V
BAT
100mA 200mA
400mA
6.49k
1%
TOTAL OUTPUT CURRENT
P
LED
/PIN
LED = 2015 HPW AOT
3.2
3.4
3.6 3.8
V
BAT
(V)
4
4.2
4.4
3217 TA01b
3217fa
1
LTC3217
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW
GND1
12 C2M
17
11 EN2
10 I
SET2
9
5
LED2
6
LED3
7
LED4
8
GND2
I
SET1
V
BAT
C1M
C2P
C1P 1
CPO 2
EN1 3
LED1 4
16 15 14 13
V
BAT
, CPO to GND......................................... –0.3V to 6V
EN1, EN2......................................–0.3V to (V
BAT
+ 0.3V)
I
CPO
(Note 2) ........................................................600mA
I
ILED1-4
(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
UD PACKAGE
16-LEAD (3mm 3mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 68°C/W
EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3217EUD#PBF
TAPE AND REEL
LTC3217EUD#TRPBF
PART MARKING
LBTQ
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic QFN
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
BAT
= 3.6V, C1 = C2 = C3 = C4 = 2.2μF unless otherwise noted.
,
PARAMETER
V
BAT
Operating Voltage
I
VBAT
Operating Current
R
ISET1
= R
ISET2
= 20k, EN1 = EN2 = High
I
CPO
= 0mA, 1x Mode
I
CPO
= 0mA, 1.5x Mode
I
CPO
= 0mA, 2x Mode
CONDITIONS
●
ELECTRICAL CHARACTERISTICS
MIN
2.9
TYP
MAX
4.5
UNITS
V
mA
mA
mA
μA
1
4
6
4
V
BAT
Shutdown Current
LED 1-4 Current
LED Current Ratio (I
LED
/I
SET1/2
)
LED Dropout Voltage
Mode Switching Delay
LED Current Matching
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
CLOCK Frequency
V
BAT
= 3.4V, V
CPO
≤ 4.6V (Note 5)
V
BAT
= 3.2V, V
CPO
≤ 5.1V (Note 5)
●
I
LED
= 25mA to 100mA
Mode Switch Threshold, I
LED
= 100mA
EN1 Only
Any Two Outputs, I
LED
= 100mA
I
CPO
= 0mA
I
CPO
= 0mA
I
CPO
= 0mA
●
370
400
330
2.5
1
V
BAT
4.5
5.05
0.5
2.8
3.2
430
mA/mA
mV
ms
%
V
V
V
Ω
Ω
Ω
0.6
0.85
1.15
MHz
3217fa
2
LTC3217
ELECTRICAL CHARACTERISTICS
CPO Short Circuit Detection
Threshold Voltage
Test Current
Unused LED Detection
Threshold Voltage
Test Current
EN1, EN2
Low Level Input Voltage (V
IL
)
High Level Input Voltage (V
IH
)
Input Current (I
IH
)
Input Current (I
IL
)
Minimum PWM On-Time
Maximum PWM Off-Time
I
SET1
, I
SET2
V
ISET1
,
ISET2
I
ISET1
,
ISET2
Current Range
I
ISET1
,
ISET2
Short-Circuit Current
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 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
I
LED1-4
= 12.5mA
●
●
●
●
●
●
●
The
l
denotes the specifications which apply over the full operating
,
temperature range, otherwise specifications are at T
A
= 25°C. V
BAT
= 3.6V, C1 = C2 = C3 = C4 = 2.2μF unless otherwise noted.
0.4
10
0.5
4
1.3
30
1.5
16
0.4
1.4
7
–1
50
1
1.175
31.25
800
1.215
1.255
375
30
1
V
mA
V
μA
V
V
μA
μA
μs
ms
V
μA
μA
CPO = 0V, EN1 = EN2 = Low
V
CPO
– LED
LED Tied to CPO
●
●
●
EN2 Only
EN2 to Remain Enabled, EN1 = Low
●
●
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 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.
Note 5:
1.5x mode output impedance is defined as (1.5V
BAT
– V
CPO
)/I
OUT
.
2x mode output impedance is defined as (2V
BAT
– V
CPO
)/I
OUT
.
TYPICAL PERFORMANCE CHARACTERISTICS
LED Dropout Voltage
vs LED Current
400
V
BAT
= 3.6V
120
100
LED PIN CURRENT (mA)
300
80
T
A
= 25°C unless otherwise noted.
LED Pin Current
vs LED Pin Voltage
V
BAT
= 3.6V
120
100
80
I
LED
(mA)
1.0
3217 G02
I
LED
vs R
ISET
LED DROPOUT VOLTAGE (mV)
200
60
40
20
60
40
20
0
100
0
10 20
30
40 50 60 70 80
LED CURRENT (mA)
90 100
3217 G01
0
0
0.2
0.4
0.6
0.8
LED PIN VOLTAGE (V)
0
5
10 15 20 25 30 35 40 45 50
R
ISET
(kΩ)
3217 G03
3217fa
3
LTC3217
TYPICAL PERFORMANCE CHARACTERISTICS
1x Mode Switch Resistance
vs Temperature
0.65
0.60
SWITCH RESISTANCE (Ω)
SWITCH RESISTANCE (Ω)
0.55
V
BAT
= 3.6V
0.50
V
BAT
= 3.3V
0.45
0.40
0.35
–40
V
BAT
= 3.9V
I
CPO
= 200mA
3.2
3.0
2.8
2.6
2.4
2.2
2.0
–40
T
A
= 25°C unless otherwise noted.
2x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(2V
BAT
– V
CPO
)/I
CPO
3.8
3.6
SWITCH RESISTANCE (Ω)
3.4
3.2
3.0
2.8
2.6
–40
V
BAT
= 3V
V
CPO
= 4.8V
C2 = C3 = C4 = 2.2μF
1.5x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(1.5V
BAT
– V
CPO
)/I
CPO
V
BAT
= 3V
V
CPO
= 4.2V
C2 = C3 = C4 = 2.2μF
–15
10
35
TEMPERATURE (°C)
60
85
3217 G04
–15
10
35
TEMPERATURE (°C)
60
85
3217 G05
–15
10
35
TEMPERATURE (°C)
60
85
3217 G06
V
BAT
Shutdown Current
vs V
BAT
Voltage
7.5
V
BAT
SHUTDOWN CURRENT (μA)
6.5
5.5
T
A
= 85°C
4.5
3.5
2.5
1.5
2.9
T
A
= 25°C
FREQUENCY (kHz)
T
A
= –40°C
980
970
Oscillator Frequency
vs Supply Voltage
100
90
EFFICIENCY (P
LED
/PIN) (%)
80
70
60
50
40
30
20
10
2.9 3.1
3.3 3.5 3.7 3.9 4.1
V
BAT
SUPPLY VOLTAGE (V)
4.3
0
4.5
Efficiency vs V
BAT
100mA 200mA
400mA
960
950
940
930
920
910
900
890
3.1
3.3
3.7 3.9 4.1
V
BAT
VOLTAGE (V)
3.5
4.3
4.5
880
T
A
= 25°C
T
A
= –40°C
T
A
= 85°C
TOTAL OUTPUT CURRENT
P
LED
/PIN
LED = 2015 HPW AOT
3
3.2
3.4
3.6 3.8
V
BAT
(V)
4
4.2
4.4
3217 G07
3217 G08
3217 G09
1.5x Mode CPO Output Ripple
2x Mode CPO Output Ripple
Charge Pump Mode Switching
and Input Current to Ground
(400mA Load)
2x
V
CPO
1x
1V/DIV NO LOAD
1x
1.5x
(5V)
V
CPO
50mV/DIV
AC-COUPLED
V
CPO
20mV/DIV
AC-COUPLED
I
VBAT
500mA/DIV
0
EN1
5V/DIV
DROPOUT
DROPOUT
V
BAT
= 3.6V
I
CPO
= 400mA
C
CPO
= 2.2μF
500ns/DIV
3217 G10
V
BAT
= 3.6V
I
CPO
= 400mA
C
CPO
= 2.2μF
500ns/DIV
3217 G11
V
IN
= 3.6V
1ms/DIV
3217 G12
3217fa
4
LTC3217
TYPICAL PERFORMANCE CHARACTERISTICS
1.5x Mode CPO Voltage
vs Load Current
4.8
4.6
3.4V
CPO VOLTAGE (V)
4.4
4.2
3.3V
4.0
3.2V
3.8
3.6
0
100
200
300
400
LOAD CURRENT (mA)
500
3217 G13
T
A
= 25°C unless otherwise noted.
2x Mode CPO Voltage
vs Load Current
C2 = C3 = C4 = 2.2μF
5.2
5.1
5.0
CPO VOLTAGE (V)
3.5V
3.6V
4.9
4.8
4.7
4.6
4.5
4.4
4.3
4.2
0
C2 = C3 = C4 = 2.2μF
3.6V
3.3V
3.2V
3.1V
V
BAT
= 3V
3.1V
V
BAT
= 3V
100
300
400
200
LOAD CURRENT (mA)
500
3217 G14
PIN FUNCTIONS
C1P C2P C1M, C2M (Pins 1, 16, 14, 12):
Charge Pump
,
,
Flying Capacitor Pins. A 2.2μF X7R or X5R ceramic capacitor
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
0
0
1
1
MODE
Shutdown
Low Current
High Current
Low + High Current
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
I
SET1
and I
SET2
to GND. With the LTC3217, 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 con-
nected directly to a low impedance ground plane.
I
SET1
/I
SET2
(Pins 9, 10):
LED Current Programming Re-
sistor Pins. The I
SET1
and I
SET2
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 overcurrent shutdown.
GND1 (Pin 13):
Charge Pump Ground. This pin should be
connected directly to a low impedance ground plane.
V
BAT
(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.
3217fa
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
5
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