LM3555TLE Datasheet, PDF (23/33 Pages) Texas Instruments – LM3555 Synchronous Boost Converter with 500 mA High Side LED Driver and Dual-Mode Control Interface

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I²C CONTROL STATE DIAGRAM
Shutdown
External
Torch
Standby
LM3555
SNVS594E – JANUARY 2009 – REVISED NOVEMBER 2011
Output On
Internal
Flash
Strobe Flash
Edge
Strobe Flash
Level
Red
Indicator
Assist Light
External
Torch
I²C MODE TRUTH TABLE
I²C/EN = ‘1’, SCL and SDA = ‘X’
OEN
0
0
0
0
0
0
1
1
1
1
1
1
1
OM1
0
0
0
0
1
1
0
0
0
1
1
1
1
OM0
0
0
0
1
0
1
0
0
1
0
1
1
1
TEN
0
1
1
X
X
X
X
X
X
X
X
X
X
SEN
X
X
X
X
X
X
X
X
X
X
0
1
1
TORCH
X
0
1
X
X
X
0
1
X
X
X
X
X
STROBE
X
X
X
X
X
X
X
X
X
X
X
0
1
Mode
Standby
Standby
Ext Torch
Standby
Standby
Standby
Standby
Ext Torch
Indicator
Assist
Internal Flash
Standby
Strobe Flash
Application Information
INTERNAL DIODE DETECTION
During the LM3555's startup sequence, an internal voltage comparator on the VLED pin monitors the forward
voltage of the LED or LEDs. This measurement occurs when the ramp-up current reaches 80 mA. If at this time
the diode voltage exceeds the user-selectable diode detect threshold (Register 0x02 bits VO1 and VO0), the
LM3555 will assume two series LEDs are present and will limit the maximum flash current to 400 mA. The four
adjustable levels are; '00' = 4.35V, '01' = 4.65V, '10' = 4.05V and '11' = 4.95V. This detection feature can be
disabled by setting the Diode Detect Enable bit (DEN) in the Current Set Register (address 0x03) to a '0'. The
DEN bit is set to a '1' (Enabled) by default.
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