LM3559TLX National Semiconductor Corporation, LM3559TLX Datasheet - Page 14

• Manufacturer Part Number: LM3559TLX
• Description: Synchronous Boost Flash Driver With Dual 900 Ma High Side Current Sources 1.8a Total Flash Current
• Manufacturer: National Semiconductor Corporation

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After the Flash pulse terminates; either by a flash timeout,
pulling STROBE low or disabling it via the I
terface, LED1 and LED2 turn completely off. This happens
even when Torch is enabled via the I
and the Flash pulse is turned on by toggling STROBE. After
a Flash event ends, the EN1, EN0 bits (bits [1:0] of the Enable
Register) are automatically 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 if Privacy mode had been enabled before the flash
pulse.
FLASH TIMEOUT
The Flash Timeout period sets the amount of time that the
Flash Current is being 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 Timeout
FIGURE 1. LED Current for STROBE (Level Triggered, Enable Register Bit [5] = 0)
FIGURE 2. LED Current for STROBE (Edge Triggered, Enable Register Bit [5] = 1)
STROBE Goes Low Before the End of the Programmed Timeout Duration
2
C-compatible interface,
2
C-compatible in-
14
durations in steps of 32 ms giving a Flash timeout range of 32
ms to 1024 ms (see
TORCH MODE
In Torch mode the current sources LED1 and LED2 each
provide 8 different current levels
tivated by setting Enable Register bits [1:0] to (1, 0). Once
Torch mode is enabled, the current sources will ramp up to
the programmed Torch current level by stepping through all
of the Torch currents at (32 µs/step) until the programmed
Torch current level is reached.
PRIVACY INDICATOR MODE
The current sources (LED1 and/or LED2) can also be used
as a privacy indicator before and after flash mode. Privacy
indicate mode is enabled by setting the Enable Register bit
[1:0] to (0,1). Additionally, the Privacy Register contains the
bits to select which current source to use as the privacy indi-
cator (either LED1, LED2, or both), whether or not the privacy
Table
5).
(Table
3). Torch mode is ac-
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