LTC3208 Datasheet, PDF (12/24 Pages) Linear Technology – High Current Software Confi gurable Multidisplay LED Controller

LTC3208
U
OPERATIO
Disabling Current Source Outputs
Unused CAM, SUB and MAIN outputs can be disabled by
using two different methods depending on the application
requirement. If the entire group is to be disabled (ie MAIN),
then the data register for that group is written to zero. The
unused outputs can be open circuit. If one or more of the
group outputs is to be enabled then the unused outputs
must be connected to CPO to prevent a false dropout
signal from occurring.
AUX has a mixture of disable requirements. If AUX is not
used then the data register is written to zero and all out-
puts can be left open circuit. If one or more output is to
be enabled then AUX1, AUX2 and AUX3 can be disabled
by connecting the unused output to CPO. AUX 4 cannot
be disabled by connecting to CPO but can be left open
circuit if X_RGBDROP is set high. This setting removes the
dropout detector from the AUX4 output but also removes
the dropout detectors from the RED, GRN and BLUE LED
outputs. To avoid disabling the RED, GRN and BLUE
dropout detectors, AUX4 should be one of the enabled
outputs whenever a mixture of enabled and disabled AUX
outputs are used.
RED, GRN and BLUE outputs are disabled by writing the
unused output register to zero. The unused output can
be left open circuit.
CAMHL
The CAMHL pin quickly selects the camera high register
for flash applications without reaccessing the I²C port.
When low, the CAM current range will be controlled by
the camera low 4-bit register. When CAMHL is asserted
high, the current range will be set by the camera high
4-bit register.
ENRGBS Pin
The ENRGBS pin can be used to enable or disable the
LTC3208 without re-accessing the I²C port. This might be
useful to indicate an incoming phone call without waking
the microcontroller. ENRGBS can be software programmed
as an independent control for either the RGB display or
the SUB display. Options REGG bit G1 determines which
display ENRGBS controls. When bit G1 is 0, the ENRGBS
pin controls the RGB display. If it is set to 1, then ENRGBS
controls the SUB display.
To use the ENRGBS pin, the I²C port must first be configured
to the desired setting. For example, if the ENRGBS pin will
be used to control the SUB display, then a nonzero code
must reside in REGD and Command register REGG bit
G1 must be set to 1. Now when ENRGBS is high (DV_CC),
the SUB display will be on with the REGD setting. When
ENRGBS is low the SUB display will be off. If no other
displays are programmed to be on, the entire chip will
be in shutdown.
Likewise if ENRGBS will be used to enable the RGB display,
then a nonzero code must reside in one of the RED, GREEN
or BLUE registers REGA1, REGA2 or REGB1, and options
register REGG bit G1 is set to 0. Now when ENRGBS is high
(DV_CC), the RGB display will light with the programmed
color. When ENRGBS is low, the RGB display will be off.
If no other displays are programmed to be on, the entire
chip will be in shutdown.
If options register REGG bit G1 is set to 1 (SUB display
control), then ENRGBS will have no effect on the RGB
display. Likewise, if bit G1 is set to 0 (RGB display control),
then ENRGBS will have no effect on the SUB display.
If the ENRGBS pin is not used, it must be connected to
DV_CC. It should not be grounded or left floating.
Thermal Protection
The LTC3208 has built-in overtemperature protection.
At internal die temperatures of around 150°C thermal
shutdown will occur. This will disable all of the current
sources and charge pump until the die has cooled by about
15°C. This thermal cycling will continue until the fault has
been corrected.
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