LM3560 Datasheet, PDF (16/42 Pages) Texas Instruments – LM3560 Synchronous Boost Flash Driver w/ Dual 1A High-Side Current Sources (2A Total Flash Current)

Privacy Current
Setting
(Enable Register Bit
[2])
0 = 31.25mA peak
1 = 250mA peak
1
1
1
1
Privacy Indicate Duty
Cycle
Privacy Register Bits[2:0]
see (Table 4)
100
101
110
111
ILED1 or ILED2
(Single LED)
125 mA
150 mA
175 mA
200 mA
POWER AMPLIFIER SYNCHRONIZATION (TX1)
The TX1/TORCH/GPIO1 pin has a triple function. With Con-
figuration Register 1 Bit [7] = 0 (default) TX1/TORCH/GPIO1
is a Power Amplifier Synchronization input (TX1 mode). This
mode is designed to reduce the flash LED current when TX1
is driven high (active high polarity) or driven low (active low
polarity). When the LM3560 is engaged in a Flash event and
TX1/TORCH is driven high, the active current sources (LED1
and/or 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 will return to the pre-
vious Flash current level. At the end of the Flash timeout,
whether the TX1/TORCH pin is high or low, the LED current
will turn off.
The polarity of TX1 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 LM3560 will be forced into Torch mode
when TX1/TORCH is pulled low. Figure 4 details the func-
tionality of the TX1 Interrupt.
TX1 Shutdown
TX1 also has the capability to force shutdown. Bit [4] of Con-
figuration Register 2 set to a '1', changes TX1 from a force
Torch when active to a force shutdown when active. For ex-
ample, if TX1/TORCH/GPIO1 is configured for TX1 mode with
active high polarity, and bit[4] of Configuration Register 2 is
set to '1' , then when TX1 is driven high, the active current
sources (LED1 and/or LED2) will be forced into shutdown.
Once the active current sources are forced into shutdown by
activating TX1, the current sources can only be re-enabled
into flash mode if TX1 is pulled low and the Flags Register is
read back. If only the Flags register is read back and TX1 is
kept high the device will be re-enabled into torch mode and
not shutdown. This occurs because the TX1 shutdown feature
is an edge-triggered event. With active high polarity the TX1
shutdown requires a rising edge at TX1 in order to force the
current source into shutdown. Once shut down, it takes a
readback of the flags Register and another rising edge at TX1
to force shutdown again. Figure 6 details the different re-
sponses of the TX1 shutdown mode.
FIGURE 4. TX1 or TX2 Interrupt (Force Torch) Response
30113807
HARDWARE TORCH
With Configuration Register 1 Bit [7] = 1, TX1/TORCH/GPIO1
is configured as a hardware Torch mode enable. In this mode,
a high at TX1/TORCH turns on the LED current at the pro-
grammed Torch current setting. The STROBE input and I²C
Enabled flash takes precedence over TORCH mode. In hard-
ware torch mode, both LED1 and LED2 current sources will
turn off after a flash event and Configuration Register 1 Bit [7]
will be reset to 0. In this situation, to re-enter torch mode via
hardware torch, the hardware torch enable bit (Configuration
Register 1 Bit [7]) must be reset to 1. Figure 5 details the
functionality of hardware torch mode.
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