Texas Instruments LM3549 Evaluation Board LM3549SQEV/NOPB LM3549SQEV/NOPB 数据表
产品代码
LM3549SQEV/NOPB
VIN
VOUT
VDx
Driver
current limit
Buck-boost
converter
SNVS640A – AUGUST 2010 – REVISED MAY 2013
LED SHORT FAULT
Short fault is detected when VOUT < 1.0V at the end of a color. Short fault is generated when VOUT is shorted
to driver by soldering defect or faulty LED. Driver current limit limits the maximum current. Depending on output
current and positive limit settings, LED short can also generate OCP fault to fault register.
to driver by soldering defect or faulty LED. Driver current limit limits the maximum current. Depending on output
current and positive limit settings, LED short can also generate OCP fault to fault register.
Figure 20. LED Short Fault
TSD FAULT
Thermal shutdown (TSD) fault is generated if junction temperature rises above TSD level. TSD engages at T
J
=
150°C (typ) and disengages at T
J
= 140°C (typ). TSD sets device to standby mode. Occasionally a false TSD
fault is generated to Fault register when device goes from shutdown mode to standby mode. It is good practice to
reset the fault register by reading it every time after device is set from shutdown mode to standby mode.
reset the fault register by reading it every time after device is set from shutdown mode to standby mode.
UVLO FAULT
Under voltage lock out (UVLO) fault is generated if VIN drops below UVLO level (~2.5V). UVLO sets device to
standby mode. When VIN rises back above the 2.5V device exits UVLO. If control register values were changed
from EEPROM defaults they need to be rewritten to registers because UVLO condition can generate EEPROM
read sequence.
standby mode. When VIN rises back above the 2.5V device exits UVLO. If control register values were changed
from EEPROM defaults they need to be rewritten to registers because UVLO condition can generate EEPROM
read sequence.
OVER CURRENT PROTECTION FAULT
Over current protection (OCP) fault is generated when positive current limit is active at the end of a color. It is
important to notice that OCP fault is not always set when positive current limit is activated. Positive current limit
can activate during normal operation when buck-boost is adjusting the output voltage to a higher level. OCP can
be caused by short from VOUT to GND, short from driver to GND or if too low positive current limit value is set
for desired output current.
important to notice that OCP fault is not always set when positive current limit is activated. Positive current limit
can activate during normal operation when buck-boost is adjusting the output voltage to a higher level. OCP can
be caused by short from VOUT to GND, short from driver to GND or if too low positive current limit value is set
for desired output current.
I
2
C Compatible Interface
I
2
C ADDRESS
LM3549 I
2
C address is 36 hex (7 bits).
I
2
C SIGNALS
The SCL pin is used for the I
2
C clock and the SDA pin is used for bidirectional data transfer. Both these signals
need a pull-up resistor according to I
2
C specification. The values of the pull-up resistors are determined by the
capacitance of the bus (typ. ~1.8k). Signal timing specifications are shown in
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