LM3560 Datasheet, PDF (14/42 Pages) Texas Instruments – LM3560 Synchronous Boost Flash Driver w/ Dual 1A High-Side Current Sources (2A Total Flash Current)

FLASH MODE
In Flash mode the LED current sources (LED1 and LED2)
each provide 16 different current levels from typically 62.5 mA
(total) to 2A (total) in steps of 62.5 mA. The Flash currents are
adjusted via the Flash Brightness Register. Flash mode is
activated by writing a (1, 1) to bits [1:0] of the Enable Register
or by enabling the hardware flash input (STROBE) via bit [2]
of Configuration Register 1, and then pulling the STROBE pin
high (high polarity). Once the Flash sequence is activated the
active current sources (LED1 and/or LED2) will ramp up to
their programmed Flash current level by stepping through all
Torch and Flash levels (32 µs/step) until the programmed
current is reached.
Bit [5] of the Enable Register (STROBE Level/Edge bit) de-
termines how the Flash pulse terminates after STROBE goes
high. With the Level/Edge bit = 1, the Flash current will only
terminate when it reaches the end of the Flash Timeout peri-
od. With the Level/Edge bit = 0, Flash mode can be terminated
by pulling STROBE low, programming bits [1:0] of the Enable
Register with (0,0), or by allowing the Flash Timeout period
to elapse. If the Level/Edge bit = 0 and STROBE is toggled
before the end of the Flash Timeout period, the Timeout pe-
riod will reset. Figure 1 and Figure 2 detail the Flash pulse
termination for the different Level/Edge bit settings.
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FIGURE 1. LED Current for STROBE (Level Triggered, Enable Register Bit 5 = 0)
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FIGURE 2. LED Current for STROBE (Edge Triggered, Enable Register Bit 5 = 1)
After the Flash pulse terminates, either by a flash timeout,
pulling STROBE low, or disabling it via the I²C-compatible in-
terface, LED1 and LED2 turn completely off. This happens
even when Torch is enabled via the I²C-compatible interface
and the Flash pulse is turned on by toggling STROBE. After
a Flash event ends, bits [1:0] of the Enable Register are au-
tomatically reset with (0, 0). The exception occurs when the
Privacy Terminate Bit is low (bit [3]) in the Privacy Register.
In this case, the specific current source that is enabled for
privacy mode will turn back on after the flash pulse.
FLASH TIMEOUT
The Flash Timeout period sets the maximum amount of time
that the Flash Current will be sourced from current sources
LED1 and LED2. Bits [4:0] of the Flash Duration Register set
the Flash Timeout period. There are 32 different Flash Time-
out durations in steps of 32 ms giving a Flash Timeout range
of 32 ms to 1024 ms (see Table 15).
TORCH MODE
In Torch mode the current sources LED1 and LED2 each
provide 8 different current levels (Table 13). Torch mode is
activated by setting Enable Register bits [1:0] to (1, 0). Once
Torch mode is enabled, the current sources will ramp up to
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