LM3556_15 Datasheet, PDF (23/39 Pages) Texas Instruments – Synchronous Boost LED Flash Driver With High-Side Current Source

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t_PERIOD
tACTIVE
t_PERIOD
t_PERIOD
LM3556
SNVS796D – AUGUST 2011 – REVISED OCTOBER 2015
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Figure 39. Multiple Pulse With Dead Time
7.6.1.7 Torch Ramp Time Register (0x06)
Bit 7
RFU
Bit 6
RFU
Bit 5
Table 8. Torch Ramp Time Register
Bit 4
Torch Ramp-Up Time
000 = 16 ms (default)
001 = 32 ms
010 = 64 ms
011 = 128 ms
100 = 256 ms
101 = 512 ms
110 = 1.024 s
111 = 2.048 s
Bit 3
Bit 2
Bit 1
Bit 0
Torch Ramp-Down Time
000 = 16 ms (default)
001 = 32 ms
010 = 64 ms
011 = 128 ms
100 = 256 ms
101 = 512 ms
110 = 1.024 s
111 = 2.048 s
7.6.1.8 Configuration Register (0x07)
Table 9. Configuration Register Description
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Strobe Usage
0 = Edge
(default)
1 = Level
Strobe Pin
Polarity
0 = Active Low
1 = Active
High (default)
Torch Pin
Polarity
0 = Active Low
1 = Active
High (default)
TX Pin
Polarity
0 = Active Low
1 = Active
High (default)
TX Event Level
0 = Off
1 = Torch Current
(default)
IVFM Enable
0 = Disabled
(default)
1 = Enabled
NTC Mode
0 = Normal
(default)
1 = Monitor
Strobe Usage Level or edge. Flash follows strobe timing if Level and internal timing if edge.
Bit 0
Indicator Mode
0 = Internal
(default)
1 = External
Strobe Polarity Active high or active low select.
Torch Polarity Active high or active low select.
TX Polarity Active high or active low select.
TX Event Level Transition to torch current level or off setting if TX event occurs.
The TX Event Level off setting is designed to force a shutdown only during a flash event. When
Torch or Indicator Mode is enabled, and a TX event occurs with the TX event level set to Off , the
LM3556 does not shut down. The TX flag bit (bit7 in the Table 14) is set, and the mode bits (bit0
and bit1 in Table 12) get locked out until the fault register is cleared via an I²C read. Because a TX
event is periodic and frequently occurring, clearing the fault register becomes more difficult.
Depending on the I²C read/write speed and TX event frequency, it may be necessary to set the TX
enable bit (bit6 in the Table 12) to a '0' before clearing the fault register to prevent future flag sets.
IVFM Enable Enables input voltage flash monitoring.
NTC Mode Monitor Mode (report only) or Normal Mode (reduce current or shutdown).
Indicator Mode Externally generated via TORCH pin or internally generated PWM.
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