Torch and

Charge (5.0V)

5.0V

3.0V

VCAP = 3.0V VCAP = 5.0V

IOUT > IMAX

T2 bit

6HW WR µ0¶

Flash

200 mA

120 mA

60 mA

VCAP

ITORCH

Time

Time

4.75V

19

LM3550

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SNVS569C – MAY 2009 – REVISED OCTOBER 2016

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Device Functional Modes (continued)

Figure 40. Torch Current Diagram

7.4.1.6 Flash State

When entered, the flash state of the LM3550 device delivers a high-current burst of current to the flash LEDs. To

enter the flash state, the flash bit in the General Purpose Register must be set to a 1 or the STROBE pin must

be pulled high (edge or level sensitive). The flash duration and current level are user adjustable via the I2C

interface (F2-F0 in current control and FD3-FD0 in options).

By default, a flash does not occur if the super-capacitor is not fully charged (that is, the end-of-charge flag (EOC

pin) must transition low). If the flash state was entered via the I2C interface (flash bit = 1 ), the LM3550

automatically resets the flash bit and the torch bit to 0 upon completion of the flash. Additionally, after the flash

event has occurred, the LM3550 returns to the charge state/mode that was in operation before the flash event

with the exception of optimal charge mode. (If optimal charge mode was used before a flash, all charging is

halted after the flash.)

7.4.1.7 EOC Functionality

The EOC pin of the device provides an indicator alerting the controller that the super-capacitor has reached its

target voltage. The EOC pin transitions low once the capacitor reaches 95% of the target voltage for the 4.5 V, 5

V and 5.3 V modes or once the capacitor has reached the optimal charge voltage in optimal charge mode.

During operation, the LM3550 continues to monitor the voltage on the super-capacitor and updates the EOC pin

when needed. Any time a mode transition occurs during charge mode or charge and torch mode, the EOC state

is re-evaluated.

During torch mode, the EOC always indicates a charging state (EOC = 1) .