LTC3217
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 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.
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 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
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
TYPICAL APPLICATIO
C2
2.2µF
C3
2.2µF
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
C1M C2P
C2M
CPO
EFFICIENCY (P
LED
/PIN) (%)
C4
2.2µF
AOT-2015HPW-1751B
6.49k
1%
EN1
0
1
0
1
EN2
0
0
1
1
I
LED
0 (SHUTDOWN)
25mA/LED
75mA/LED
100mA/LED
3217 TA01
U
U
U
Efficiency vs V
BAT
100
90
80
70
60
50
40
30
20
10
0
3
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
100mA 200mA
400mA
3217 G09
3217f
1
LTC3217
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
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
16 15 14 13
C1P 1
CPO 2
EN1 3
LED1 4
5
6
7
8
17
12 C2M
11 EN2
10 I
SET2
9
I
SET1
LED2
LED3
LED4
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 PART NUMBER
LTC3217EUD
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.
The
●
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
GND2
GND1
V
BAT
C1M
C2P
QFN PART MARKING
LBTQ
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
2
U
MHz
3217f
W
U
U
W W
W
LTC3217
The
●
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
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:
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
I
LED1-4
= 12.5mA
●
●
●
●
●
●
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
MAX
0.4
UNITS
V
V
µA
µA
µs
ms
V
µA
µA
1.4
7
–1
50
1
1.175
31.25
800
1.215
1.255
375
30
1
EN2 Only
EN2 to Remain Enabled, EN1 = Low
●
●
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 (1.5V
BAT
– V
CPO
)/I
OUT
.
2x mode output impedance is defined as (2V
BAT
– V
CPO
)/I
OUT
.
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C unless otherwise noted.
LED Dropout Voltage
vs LED Current
400
V
BAT
= 3.6V
120
100
LED DROPOUT VOLTAGE (mV)
LED PIN CURRENT (mA)
300
200
60
40
20
I
LED
(mA)
100
0
10 20
30
40 50 60 70 80
LED CURRENT (mA)
90 100
3217 G01
U W
LED Pin Current
vs LED Pin Voltage
V
BAT
= 3.6V
I
LED
vs R
ISET
120
100
80
60
40
20
0
0
5
10 15 20 25 30 35 40 45 50
R
ISET
(kΩ)
3217 G03
80
0
0
0.2
0.4
0.6
0.8
LED PIN VOLTAGE (V)
1.0
3217 G02
3217f
3
LTC3217
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C unless otherwise noted.
1x Mode Switch Resistance
vs Temperature
0.65
0.60
SWITCH RESISTANCE (Ω)
I
CPO
= 200mA
3.2
3.0
2.8
2.6
2.4
2.2
2.0
–40
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
–15
10
35
TEMPERATURE (°C)
60
V
BAT
Shutdown Current
vs V
BAT
Voltage
7.5
V
BAT
SHUTDOWN CURRENT (µA)
6.5
T
A
= –40°C
5.5
T
A
= 85°C
4.5
3.5
2.5
1.5
2.9
T
A
= 25°C
EFFICIENCY (P
LED
/PIN) (%)
FREQUENCY (kHz)
3.1
3.3
3.7 3.9 4.1
V
BAT
VOLTAGE (V)
3.5
1.5x Mode CPO Output Ripple
V
CPO
50mV/DIV
AC COUPLED
V
BAT
= 3.6V
I
CPO
= 400mA
C
CPO
= 2.2µF
500ns/DIV
4
U W
85
3217 G04
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
3.8
3.6
3.4
3.2
3.0
2.8
2x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(2V
BAT
– V
CPO
)/I
CPO
V
BAT
= 3V
V
CPO
= 4.8V
C2 = C3 = C4 = 2.2µF
–15
10
35
TEMPERATURE (°C)
60
85
3217 G05
2.6
–40
–15
10
35
TEMPERATURE (°C)
60
85
3217 G06
Oscillator Frequency
vs Supply Voltage
980
970
960
950
940
930
920
910
900
890
4.3
4.5
Efficiency vs V
BAT
100
90
80
70
60
50
40
30
20
10
0
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
100mA 200mA
400mA
T
A
= 25°C
T
A
= –40°C
T
A
= 85°C
880
2.9 3.1
3.3 3.5 3.7 3.9 4.1 4.3
V
BAT
SUPPLY VOLTAGE (V)
4.5
3217 G07
3217 G08
3217 G09
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
20mV/DIV
AC COUPLED
I
VBAT
500mA/DIV
0
EN1
5V/DIV
DROPOUT
DROPOUT
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
3217f
LTC3217
TYPICAL PERFOR A CE CHARACTERISTICS
T
A
= 25°C unless otherwise noted.
1.5x Mode CPO Voltage
vs Load Current
4.8
4.6
3.4V
CPO VOLTAGE (V)
C2 = C3 = C4 = 2.2µF
4.4
4.2
3.3V
4.0
3.2V
3.8
3.6
0
100
200
300
400
LOAD CURRENT (mA)
3.1V
V
BAT
= 3V
CPO VOLTAGE (V)
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
0
0
1
1
MODE
Shutdown
Low Current
High Current
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
U W
2x Mode CPO Voltage
vs Load Current
5.2
5.1
5.0
3.6V
C2 = C3 = C4 = 2.2µF
3.5V
3.6V
4.9
4.8
4.7
4.6
4.5
4.4
4.3
3.3V
3.2V
3.1V
V
BAT
= 3V
500
3217 G13
4.2
0
100
300
400
200
LOAD CURRENT (mA)
500
3217 G14
U
U
U
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. 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.
I
SET1
/I
SET2
(Pins 9, 10):
LED Current Programming
Resistor 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 over-current 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.
3217f
5
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