Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - LED driver DC-DC voltage regulator QFN 16 EP Surface-mount

LTC3217

3217fa

BAT

(V)

EFFICIENCY (P

LED

/PIN) (%)

100

3.4

3.8

3217 TA01b

3.2

3.6

4.2

4.4

TOTAL OUTPUT CURRENT

LED

/PIN

LED = 2015 HPW AOT

100mA

200mA

400mA

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

600mA Low Noise

Multi-LED Camera Light

Charge Pumps

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 efﬁ ciency 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 ﬁ rst 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 Efﬁ ciency 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

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.

Efﬁ ciency vs V

BAT

2.2

μF

2.2

μF

2.2

μF

BAT

19.6k

6.49k

LED1

LED2

LED3

LED4

GND

BAT

EN2

EN1

LTC3217

C1P C1M C2P C2M

2.2μF

AOT-2015HPW-1751B

3217 TA01

SET1

SET2

CPO

EN1 (TORCH)

EN2 (FLASH)

EN1

0 (SHUTDOWN)

25mA/LED

75mA/LED

100mA/LED

EN2 I

LED

Summary of content (12 pages)

PAGE 1
LTC3217 600mA Low Noise Multi-LED Camera Light Charge Pumps DESCRIPTION FEATURES n n n n n n n n n n n n Charge Pump Provides High Efﬁciency with Automatic Mode Switching Multimode Operation: 1x, 1.
PAGE 2
LTC3217 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) GND1 C1M C2P VBAT TOP VIEW 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)....
PAGE 3
LTC3217 ELECTRICAL CHARACTERISTICS The l 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. CPO Short Circuit Detection ● 0.4 1.3 V CPO = 0V, EN1 = EN2 = Low ● 10 30 mA Threshold Voltage VCPO – LED ● 0.5 1.5 V Test Current LED Tied to CPO ● 4 16 μA 0.
PAGE 4
LTC3217 TYPICAL PERFORMANCE CHARACTERISTICS 1.5x Mode Charge Pump Open-Loop Output Resistance vs Temperature (1.5VBAT – VCPO)/ICPO 3.2 ICPO = 200mA 3.0 SWITCH RESISTANCE (Ω) 0.55 VBAT = 3.6V 0.50 VBAT = 3.3V VBAT = 3.9V 0.45 3.8 VBAT = 3V VCPO = 4.2V C2 = C3 = C4 = 2.2μF 2.8 2.6 2.4 0.35 –40 3.2 3.0 –15 10 35 TEMPERATURE (°C) 2.0 –40 85 60 2.8 –15 10 35 TEMPERATURE (°C) 7.5 6.5 FREQUENCY (kHz) TA = –40°C TA = 85°C 4.
PAGE 5
LTC3217 TYPICAL PERFORMANCE CHARACTERISTICS 1.5x Mode CPO Voltage vs Load Current 4.8 TA = 25°C unless otherwise noted. 2x Mode CPO Voltage vs Load Current 5.2 C2 = C3 = C4 = 2.2μF C2 = C3 = C4 = 2.2μF 5.1 4.6 CPO VOLTAGE (V) 4.4 3.5V 3.6V 4.2 3.3V 4.0 3.2V 100 4.8 3.3V 4.7 3.2V 4.6 3.1V 4.5 VBAT = 3V 4.3 VBAT = 3V 3.6 0 3.6V 4.9 4.4 3.1V 3.8 CPO VOLTAGE (V) 5.0 3.4V 500 200 300 400 LOAD CURRENT (mA) 3217 G13 4.
PAGE 6
LTC3217 BLOCK DIAGRAM 1 C1P 14 C1M 16 C2P 12 C2M 850kHz OSCILLATOR GND1 15 VBAT CPO 13 2 CHARGE PUMP – + ENABLE CP + CPO SHORT-CIRCUIT PROTECTION + – 9 + – – ISET1 0.8V LED1 4 LED2 LED CURRENT SOURCES MUX 10 3 1.22V ISET2 EN1 5 4 LED3 6 LED4 7 GND2 CONTROL LOGIC 8 250k 11 EN2 PWM TIMING THERMAL SHUTDOWN 250k 3217 BD OPERATION Power Management The LTC3217 uses a switched capacitor charge pump to boost CPO to as much as 2 times the input voltage up to 5.1V.
PAGE 7
LTC3217 OPERATION The LED currents are delivered by the four programmable current sources. Three discrete current settings (Low, High, Low + High) are available and may be selected via the EN1 and EN2 pins. The values of these currents may be selected by choosing the appropriate programming resistors. Each resistor is connected between the ISET1 or ISET2 pin to ground. The resistor values required to attain the desired current levels can be determined by Equation 1.
PAGE 8
LTC3217 OPERATION Shutdown Current ROL + – + 1.5VBAT OR 2VBAT CPO – 3217 F01 Figure 1. Equivalent Open-Loop Circuit VCPO in calculating Equations 2 and 3 is the minimum required voltage for the LED and not the regulated voltage. Typical values of ROL as a function of temperature are shown in Figures 2 and 3. 3.2 SWITCH RESISTANCE (Ω) 3.0 VBAT = 3V VCPO = 4.2V C2 = C3 = C4 = 2.2μF In shutdown mode all the circuitry is turned off and the LTC3217 draws a very low current from the VBAT supply.
PAGE 9
LTC3217 APPLICATIONS INFORMATION VBAT, CPO Capacitor Selection The style and value of the capacitors used with the LTC3217 determine several important parameters such as regulator control loop stability, output ripple, charge pump strength and minimum start-up time. To reduce noise and ripple, it is recommended that low equivalent series resistance (ESR) ceramic capacitors are used for both CVBAT and CCPO. Tantalum and aluminum capacitors are not recommended due to high ESR.
PAGE 10
LTC3217 APPLICATIONS INFORMATION and Y5V capacitors may also have a very poor voltage coefﬁcient causing them to lose 60% or more of their capacitance when the rated voltage is applied. Therefore, when comparing different capacitors, it is often more appropriate to compare the amount of achievable capacitance for a given case size rather than comparing the speciﬁed capacitance value.
PAGE 11
LTC3217 PACKAGE DESCRIPTION At moderate to high output power, the quiescent current of the LTC3217 is negligible and the expression shown in Equation 6 is valid. Once dropout is detected at the LED pin, the LTC3217 enables the charge pump in 1.5x mode. In 1.5x boost mode, the efﬁciency is similar to that of a linear regulator with an effective input voltage of 1.5 times the actual input voltage. This is because the input current for a 1.5x charge pump is approximately 1.5 times the load current.
PAGE 12
LTC3217 TYPICAL APPLICATION 500mA Camera Flash with PWM Brightness Control C2 2.2μF C1P VBAT C1 2.2μF C3 2.2μF C1M C2P C2M VBAT CPO C4 2.2μF LTC3217 LED1 EN1 ILED 500mA (MAX) LED2 1kHz PWM (5% TO 100% DC) LED3 EN2 ISET1 NC LED4 ISET2 3217 TA02 GND 3.92k 1% RELATED PARTS PART NUMBER LT®1618 DESCRIPTION Constant Current, Constant Voltage, 1.4MHz High Efﬁciency Boost Regulator 250mA (IOUT), 1.5MHz High Efﬁciency Step-Down Charge Pump Constant Current, 1.