VOUT

STROBE

ILED

VOUT

STROBE

ILED

OFF

PASS

BOOST

12

LM3648, LM3648TT

SNVSA68D – OCTOBER 2014 – REVISED NOVEMBER 2016

www.ti.com

Product Folder Links: LM3648 LM3648TT

Submit Documentation Feedback

Copyright © 2014–2016, Texas Instruments Incorporated

Feature Description (continued)

7.3.2 Torch Mode

In Torch mode, the LED current source (LED) provide 128 target current levels from 1.954 mA to 358 mA or

3.908 mA to 502.308 mA on LM3648TT. The Torch current is adjusted via the LED Torch Brightness Register.

Torch mode is activated by the Enable Register (setting M1, M0 to '10'), or by pulling the TORCH/TEMP pin

HIGH when the pin is enabled (Enable Register) and set to Torch Mode. Once the TORCH sequence is activated

the active current source (LED) ramps up to the programmed Torch current by stepping through all current steps

until the programmed current is reached. The rate at which the current ramps is determined by the value chosen

in the Timing Register.

Torch Mode is not affected by Flash Timeout or by a TX Interrupt event.

7.3.3 IR Mode

In IR Mode, the target LED current is equal to the value stored in the LED Flash Brightness Registers. When IR

mode is enabled (setting M1, M0 to '01'), the boost converter turns on and sets the output equal to the input

(pass-mode). At this point, toggling the STROBE pin enables and disables the LED current source (if enabled).

The STROBE pin can only be set to be Level sensitive, meaning all timing of the IR pulse is externally controlled.

In IR Mode, the current source does not ramp the LED output to the target. The current transitions immediately

from off to on and then on to off.

Figure 22. IR Mode with Boost

Figure 23. IR Mode Pass Only