LM3559 datasheet(13/50 Pages) TI1

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IFLASH

ITORCH

STROBE

TORCH

Flash Duration

IFLASH

ITORCH

STROBE

TX1 or TX2 set

for Active High

Flash Timeout

LM3559

www.ti.com

SNVS624B – JUNE 2011 – REVISED JUNE 2016

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8.3 Feature Description

8.3.1 Power Amplifier Synchronization (TX1)

The TX1/TORCH/GPIO1 pin has a triple function. With the Configuration Register 1 Bit [7] = 0 (default)

TX1/TORCH/GPIO1 is a power-amplifier-synchronization input. This mode is designed to reduce the flash LED

current when TX1 is pulled high (active high polarity) or low (active low polarity). When the LM3559 is engaged in

a flash event and the TX1/TORCH pin is pulled high, both LED1 and LED2 are forced into torch mode at the

programmed torch current setting. If TX1 is then pulled low before the flash pulse terminates, the LED current

returns to the previous flash current level. At the end of the flash timeout, whether the TX1/TORCH pin is high or

low, the current sources turn off.

The polarity of the TX1 input can be changed from active high to active low by writing a 0 to bit [5] of

Configuration Register 1. With this bit set to 0 the LM3559 is forced into torch mode when TX1/TORCH is pulled

low. Figure 25 details the functionality of the TX1 interrupt.

Figure 25. TX1 or TX2 Interrupt Event

Figure 26. Hardware-Torch Mode

8.3.2 Input Voltage Flash Monitor Fault

The VIN flash monitor flag (bit [6] of the Flags Register reads back a 1 when the input voltage flash monitor is

enabled and VIN falls below the programmed VIN flash monitor threshold. This flag must be read back in order to

resume normal operation after the LED current has been forced to the lower flash current setting.

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