LINEAR TECHNOLOGY LTC3217 Technical data

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

■

Low Noise Constant Frequency Operation*

■

PWM Brightness Control via the EN2 Pin

■

Low Shutdown Current: 4µA

■

Internal Soft-Start Limits Inrush Current During

and Enable Pins

SET

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

LTC3217

600mA Low Noise

Multi-LED Camera Light

Charge Pump

U

DESCRIPTIO

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 current set resistors to form a complete LED power
supply and current controller.

Built-in soft-start circuitry prevents excessive inrush cur­rent 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
I

. In addition, the brightness can be controlled by

SET2

pulse width modulation of the EN2 pin.

The charge pump optimizes efficiency based on the volt­age 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.

SET1

and

TYPICAL APPLICATIO

C2

2.2µFC32.2µF

C1P C1M C2P C2M

V

BAT

C1

2.2µF

EN1 (TORCH)

EN2 (FLASH)

19.6k

V

EN1

EN2

1%

BAT

I

SET1ISET2

LTC3217

6.49k
1%

CPO

LED1

LED2

LED3

LED4
GND

C4

2.2µF

EN1

0
1
0
1

U

EN2 I

0

0 (SHUTDOWN)

0

25mA/LED

1

75mA/LED

1

100mA/LED

LED

The LTC3217 is available in a low profile 16-lead (3mm ×
3mm × 0.75mm) QFN package.

3217 TA01

AOT-2015HPW-1751B

100

100mA

90

80

70

/PIN) (%)

60

LED

50

40

30

EFFICIENCY (P

20

TOTAL OUTPUT CURRENT

10

/PIN

P

LED

LED = 2015 HPW AOT

0

3

3.2

Efficiency vs V

200mA

3.6

3.4
V

BAT

(V)

3.8

BAT

400mA

4

4.4

4.2

3217 G09

3217f

1

LTC3217

16 15 14 13

5 6 7 8

TOP VIEW

17

UD PACKAGE

16-LEAD (3mm × 3mm) PLASTIC QFN

9

10

11

12

4

3

2

1C1P

CPO

EN1

LED1

C2M

EN2

I

SET2

I

SET1

C2P

V

BAT

C1M

GND1

LED2

LED3

LED4

GND2

WW

W

U

ABSOLUTE AXI U RATI GS

(Note 1)

V

, CPO to GND ....................................... –0.3V to 6V

BAT

EN1, EN2 .................................... –0.3V to (V

(Note 2) ....................................................... 600mA

I

CPO

I

(Note 3) .................................................. 150mA

ILED1-4

CPO Short-Circuit Duration ............................. Indefinite

Operating Temperature Range (Note 4) ... –40°C to 85°C

Storage Temperature Range ..................–65°C to 125°C

BAT

+ 0.3V)

UUW

PACKAGE/ORDER I FOR ATIO

T

= 125°C, θJA = 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.

JMAX

QFN PART MARKING

LBTQ

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

V

Operating Voltage

BAT

I

Operating Current R

VBAT

V

Shutdown Current 4 µA

BAT

LED 1-4 Current

LED Current Ratio (I
LED Dropout Voltage Mode Switch Threshold, I

Mode Switching Delay EN1 Only 2.5 ms
LED Current Matching Any Two Outputs, I

Charge Pump (CPO)

1x Mode Output Voltage I

1.5x Mode Output Voltage I

2x Mode Output Voltage I
1x Mode Output Impedance 0.5 Ω

1.5x Mode Output Impedance V
2x Mode Output Impedance V
CLOCK Frequency

LED/ISET1/2

)I

The ● denotes the specifications which apply over the full operating

= 25°C. V

A

ISET1

I

CPO

I

CPO

I

CPO

LED

CPO

CPO

CPO

BAT

BAT

= 3.6V, C1 = C2 = C3 = C4 = 2.2µF, unless otherwise noted.

BAT

●

2.9 4.5 V

= R

= 20k, EN1 = EN2 = High

ISET2

= 0mA, 1x Mode 1 mA
= 0mA, 1.5x Mode 4 mA

= 0mA, 2x Mode 6 mA

= 25mA to 100mA

= 100mA 330 mV

LED

= 100mA 1 %

LED

= 0mA V
= 0mA 4.5 V

= 0mA 5.05 V

= 3.4V, V
= 3.2V, V

≤ 4.6V (Note 5) 2.8 Ω

CPO

≤ 5.1V (Note 5) 3.2 Ω

CPO

●

370 400 430 mA/mA

BAT

●

0.6 0.85 1.15 MHz

V

3217f

2

LTC3217

R

ISET

(kΩ)

0

I

LED

(mA)

40

80

120

20

60

100

10 20 30 40

3217 G03

505015253545

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at T

The ● denotes the specifications which apply over the full operating

= 25°C. V

A

= 3.6V, C1 = C2 = C3 = C4 = 2.2µF, unless otherwise noted.

BAT

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

Maximum PWM Off-Time EN2 to Remain Enabled, EN1 = Low

I

, I

SET1

SET2

V

ISET1, ISET2

I

ISET1, ISET2

I

ISET1, ISET2

Current Range

Short-Circuit Current 800 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

I

LED1-4

= 12.5mA

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
2x mode output impedance is defined as (2V

●

●

1.4 V

●

730µA

●

–1 1 µA

●

50 µs

●

●

1.175 1.215 1.255 V

●

31.25 375 µA

– V

BAT

CPO

BAT

)/I

0.4 V

1ms

– V

CPO

.

OUT

)/I

.

OUT

UW

TYPICAL PERFOR A CE CHARACTERISTICS

LED Dropout Voltage
vs LED Current

400

V

= 3.6V

BAT

300

200

100

LED DROPOUT VOLTAGE (mV)

0

10

20 30 40 50

LED CURRENT (mA)

60 70 80 90 100

3217 G01

LED Pin Current
vs LED Pin Voltage

120

V

= 3.6V

BAT

100

80

60

40

LED PIN CURRENT (mA)

20

0

0

0.2 0.4 0.6 0.8
LED PIN VOLTAGE (V)

TA = 25°C unless otherwise noted.

vs R

I

LED

1.0

3217 G02

ISET

3217f

3

LTC3217

V

BAT

(V)

3

0

EFFICIENCY (P

LED

/PIN) (%)

10

30

40

50

100

70

3.4

3.8

4

3217 G09

20

80

90

60

3.2

3.6

4.2

4.4

TOTAL OUTPUT CURRENT
P

LED

/PIN

LED = 2015 HPW AOT

100mA

200mA

400mA

UW

TYPICAL PERFOR A CE CHARACTERISTICS

TA = 25°C unless otherwise noted.

1x Mode Switch Resistance
vs Temperature

0.65
I

= 200mA

CPO

0.60

SWITCH RESISTANCE (Ω)

0.55

0.50

0.45

0.40

0.35

SHUTDOWN CURRENT (µA)

BAT

V

7.5

6.5

5.5

4.5

3.5

2.5

1.5

–40

2.9

V

BAT

vs V

V

= 3.6V

BAT

V

= 3.3V

BAT

–15 10 35 60

TEMPERATURE (°C)

Shutdown Current

Voltage

BAT

TA = –40°C

TA = 85°C

3.3 3.7

3.1 3.5
V

VOLTAGE (V)

BAT

V

BAT

TA = 25°C

4.1

3.9

= 3.9V

4.3

3217 G04

3217 G07

85

4.5

1.5x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(1.5V

3.2

3.0

2.8

2.6

2.4

SWITCH RESISTANCE (Ω)

2.2

2.0
–40

– V

BAT

V

= 3V

BAT

= 4.2V

V

CPO

C2 = C3 = C4 = 2.2µF

–15 10 35 60

)/I

CPO

TEMPERATURE (°C)

CPO

Oscillator Frequency
vs Supply Voltage

980

970

960

950

940

930

920

FREQUENCY (kHz)

910

900

890

880

2.9

TA = 25°C

TA = –40°C

3.1 3.5

3.3

V

SUPPLY VOLTAGE (V)

BAT

3.7

TA = 85°C

3.9

4.1

4.3

3217 G05

3217 G08

85

4.5

2x Mode Charge Pump Open-Loop
Output Resistance vs Temperature
(2V

– V

BAT

3.8
V

BAT

V

CPO

3.6

C2 = C3 = C4 = 2.2µF

3.4

3.2

3.0

SWITCH RESISTANCE (Ω)

2.8

2.6

–40

Efficiency vs V

= 3V
= 4.8V

–15 10 35 60

)/I

CPO

CPO

TEMPERATURE (°C)

BAT

85

3217 G06

AC COUPLED

4

V

CPO

50mV/DIV

1.5x Mode CPO Output Ripple 2x Mode CPO Output Ripple

V

CPO

20mV/DIV

3217 G10

AC COUPLED

V
I
C

BAT

CPO

CPO

= 3.6V

= 400mA

= 2.2µF

500ns/DIV
I
C

BAT

CPO

CPO

= 3.6V

= 400mA

= 2.2µF

500ns/DIVV

3217 G11

V

CPO

1V/DIV

I

VBAT

500mA/DIV

EN1

5V/DIV

Charge Pump Mode Switching
and Input Current to Ground
(400mA Load)

0

V

1x

NO LOAD

= 3.6V

IN

1x

DROPOUT

1.5x

DROPOUT

1ms/DIV

2x

(5V)

3217 G12

3217f