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Any way to disable/bypass Flash Pulse Safety Timer on LM3553 LED driver?

Mike Fournier1
Prodigy 20 points
Other Parts Discussed in Thread: LM3553

Hello!

I'm using an LM3553 in a heavily heatsinked environment and require a higher continuous amperage sink than Torch mode can provide. Flash mode is providing the current levels I need, but of course only for a maximum of 3200 seconds before the safety pulse timer kills it.

Is there a method to:

  • disable the safety pulse timer entirely?
  • 'reset' the timer mid-flash (it must be storing the elapsed vs. target clock ticks in a memory address somewhere?)
  • trigger the flash event again (via the i2c interface) before the first flash event has completed?

Sending a series of Flash->Torch->Flash->Torch... events over i2c does work, but leads to unpleasant flickering in LED output due to the time needed to send the serial command.

Any suggestions?

  • 0
    Prodigy 20 points

    Nevermind, I stumbled over the solution. When the Flash event ends the controller must be put into shutdown via the General register before another Flash command can be issued. Sending a shutdown just before the safety timer duration expires then immediately sending a Flash command does the trick.

    Take note that the heat accumulates very quickly this way though - even with thermal paste and a huge heatsink area it hit shutdown temperature in under a minute of operation.