Bottom View

Die-Attach

Pad (DAP)

GND

2

3

4

5

1

14

13

12

11

15

Top View

Die-Attach

Pad (DAP)

GND

2

3

4

5

1

14

13

12

11

15

LM3550

SNVS569B – MAY 2009 – REVISED MAY 2013

www.ti.com

DESCRIPTION (CONTINUED)

The LM3550 can be configured to utilize a proprietary super-capacitor charging scheme (Optimal Charge Mode),

allowing faster charging times (0 to Target Voltage) and lower current-source power dissipation. Optimal Charge

Mode adapts to changes in the flash LEDs forward voltage as well as the super-capacitor's ESR ensuring that

the super-capacitor is charged to the ideal voltage required to sustain constant current-flash operation.

The STROBE pin allows the Flash to be toggled via a flash-enable signal from a camera module. The EOC pin

sinks current when the output voltage reaches 95% of the final value.

The ALD/TEMP input pin allows either a light sensor to adjust the flash-current level based on the ambient light

conditions, or it allows for over-temperature detection and protection of the LED during high-power operation or

high ambient-temperature conditions by connecting an NTC thermistor temperature monitoring circuit to the pin.

Connection Diagram

PIN DESCRIPTIONS

Pin #

Name

Description

14

1

anodes and Super-Capacitor to this pin.

20

C1+

18

C1-

Flying capacitor pins. 1 µF ceramic capacitor should be connected from C1+ to C1

− and C2+ to C2−.

15

C2+

16

C2-

3

LED-

Regulated current sink input, for Torch Mode.

4

FET_CON

External FET controller. Connect gate of flash NFET to this pin.

5

FB

Programmable Feedback Voltage pin.

10

SCL

8

SDA

13

IND

Indicator LED Current Source. Drives one red LED with a 5 mA current.

End-of-charge output/ flash ready. The EOC pin will transition from high to low when an end of charge

6

EOC

state has been reached

Manual Flash enable pin. The Strobe pin can be configured to be rising edge sensitive with the flash

11

STROBE

timing controlled internally, or level sensitive with the flash timing being controlled externally.

2

BAL

Super-capacitor active Balance pin.

Ambient Light Sensor or Temperature Monitoring pin. For ambient light sensing, connect a light sensor /

12

ALD/TEMP

photo-diode and a resistor to this pin. For temperature monitoring, connect a NTC thermistor from VCC to

the NTC pin and a resistor from the NTC pin to ground.

7,9,17,19, DAP

GND

Ground pins. These pins should be connected directly to a low impedance ground plane.

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

2

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