TLC5930 Datasheet, PDF (25/39 Pages) Texas Instruments – 12-CHANNEL LED DRIVER

TLC5930
PRINCIPLES OF OPERATION
SLLS528 – MARCH 2002
ALL OUTPUT FORCE ON OPERATION
OPERATION
MODE SETTING
PACKET
FORCE ON = 1
FORCE OFF = 0
HSYNC
PACKET
OTHER
PACKET
HSYNC
PACKET
OTHER
PACKET
OPERATION
MODE SETTING
PACKET
FORCE ON = 0
FORCE OFF = 0
HSYNC
PACKET
OTHER
PACKET
GRAY
SCALE
CLOCK
CONSTANT
CURRENT
OUTPUT
NORMAL
LIGHT ON
FORCE ON
DON’T CARE
IF DIFFERENT CURRENT VALUE IS SET
NORMAL
LIGHT ON
RELATION TO ALL OUTPUT FORCE OFF
OPERATION
MODE SETTING
PACKET
FORCE ON = 1
FORCE OFF = 0
HSYNC
PACKET
OTHER
PACKET
OPERATION
MODE SETTING
PACKET
FORCE ON = 0
FORCE OFF = 1
OTHER
PACKET
A
OPERATION
MODE SETTING
PACKET
FORCE ON = 0
FORCE OFF = 0
OTHER
PACKET
A
HSYNC
PACKET
GRAY
SCALE
CLOCK
CONSTANT
CURRENT
OUTPUT
NORMAL
LIGHT ON
FORCE ON
LIGHT ON BY ALL
OUTPUT FORCE OFF
DON’T CARE
LIGHT OFF BY RELEASE OF ALL OUTPUT
FORCE ON (LATCHED BY HSYNC)
FORCE ON
RE–LIGHT ON BY RELEASE OF
ALL OUTPUT FORCE OFF
UDG–0203
Figure 8. All Output Force ON Operation
Note that, in relation to all output force off shown in Figure 8, when the HSYNC packet is between the other
packet and operation mode setting packet with force-ON = 0 / force-OFF = 0, no re-light-ON happens by release
of all the output force-OFF.
OVM function
The OVM function is to compare the voltage across the constant-current output terminals (OUT0 to OUT11) with
the detection voltage set by this packet, and to output 0 as a comparison result if voltage across terminal is higher
than detection voltage and 1 if lower. The TLC5930 has one comparator per output as shown in Figure 9.
The comparison result input ORed with all the output appears in OVMFA of failure monitor information reading,
and result per output appears in OVM information reading data OVMF[0:11]. By using this function, where LED
disconnection (the voltage across output falls below 0.3 V) or LED short (the voltage across output goes
extremely high) has occurred can be detected. Also, the voltage across the constant-current output terminals
can be known when it is being turned on by changing the setting value of detection voltage, and heat-up from
the device can be minimized by controlling the voltage applied to the anode of the LED to minimize the voltage
across constant-current output (approximately 0.4 V at I_O = 40 mA) based on the resulting voltage.
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