LM3560 datasheet(22/48 Pages) TI1

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STROBE

LED Current

Timeout Duration

TX1/TORCH

ITORCH

IFLASH

LM3560

SNOSB43B – SEPTEMBER 2011 – REVISED AUGUST 2013

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Two actions can be taken when the NTC comparator is tripped. With Configuration Register 2 bit [1] set to ‘0’ the

NTC interrupt will force the LED current from Flash mode into Torch mode. With Configuration Register 2 bit [1]

set to ‘1’, the NTC interrupt will force the LED current into shutdown.

Whether in NTC force torch or NTC shutdown, in order to re-enter flash mode after an NTC event, two things

must occur. First, the NTC input must be above the 1V threshold. Secondly, the Flags Register must be read.

To avoid noise from falsely triggering the NTC Comparator, this mode incorporates a 250 µs de-glitch timer. With

NTC mode active, VLEDI/NTC must go below the trip point (VTRIP) and remain below it for 250 µs before the LEDs

are forced into Torch mode (or shutdown) and the NTC Flag is written.

ALTERNATE EXTERNAL TORCH (AET MODE)

With Configuration Register 2 bit [2] set to '1', the LM3560 is configured for AET mode, and the operation of

TX1/TORCH becomes dependent on its occurrence relative to the STROBE input. In this mode, if TX1/TORCH

goes high first, then STROBE goes high, the LEDs are forced into Torch mode with no timeout. In this mode, if

TX1/TORCH goes high after STROBE has gone high, then the TX1/TORCH pin operates as a normal LED

current interrupt (TX1), and the LEDs will turn off at the end of the timeout duration (see Figure 35).

Figure 35. AET Mode Timing

INPUT VOLTAGE MONITOR

The LM3560 has an internal comparator at IN which monitors the input voltage and can force the LED current

into Torch mode or into shutdown if VIN falls below the programmable VIN Monitor Threshold. Bit 0 in the VIN

Monitor Register enables or disables this feature. When enabled, Bits [2:1] program the 4 adjustable thresholds

of 2.9V, 3.0V, 3.1V, and 3.2V. Bit 3 in Configuration Register 2 selects whether a VIN Monitor event forces Torch

mode or forces LED1 and/or LED2 into shutdown. See Table 12 for additional information. When the input

voltage monitor is active, and VIN falls below the programmed VIN Monitor threshold, the LEDs will either turn off

or be forced into the Torch current setting. To reset the LED current to its previous level, two things must occur.

First, VIN must go above the VIN Monitor threshold, and the Flags register must be read back. See Figure 36 for

the VIN Monitor Timing Waveform.

To avoid noise from falsely triggering the VIN Monitor, this mode incorporates a 250 µs de-glitch timer. With the

VIN Monitor active, VIN must go below the VIN Monitor Threshold (VIN_TH), and remain below it, for 250 µs before

the LEDs are forced into Torch mode (or shutdown) and the VIN Monitor Flag is written.

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LM3560 Datasheet(PDF) 22 Page - Texas Instruments