TLC59108F_15 Datasheet, PDF (23/37 Pages) Texas Instruments – 8-Bit FM+ I2C Bus LED Driver

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9 Application and Implementation
TLC59108F
SLDS162B – MARCH 2009 – REVISED DECEMBER 2015
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
9.1.1 Setting LED Current
The LED current is primarily dependent on the supply voltage, the forward voltage of the LED, and the series
resistor (R_SET). In many applications the supply voltage and LED forward voltage cannot be adjusted. Hence,
R_SET is used to adjust the LED current. This calculation is discussed in detail in the typical application example.
9.1.2 PWM Brightness Dimming
The perceived brightness of the LEDs can be adjusted by use of PWM dimming. For example, an LED driven at
50% duty cycle will appear less bright than it would at 100% duty cycle. The TLC59116F offers duty cycle control
for each individual channel and also offers group duty cycle control. Refer to the Register Maps for details
regarding programmable duty cycle.
9.1.3 TLC59108 and TLC59108F Differences
The TLC59108 and TLC59108F are similar devices with the difference being the output structure. The TLC59108
has 8 constant-current outputs while the TLC59108F has 8 open-drain outputs. The REXT is used to program
the current on the TLC59108 for all channels. The in-line resistors on the OUT pins are used in conjunction with
the VLED to set the currents on each TLC59108F channel. Because the resistors are unique for each output, the
currents can be set by output by changing the resistor value.
LEDs: 8 LEDs / TLC59108 * 1 TLC59108 = 8 LEDs
LEDs: 8 LEDs / TLC59108F * 1 TLC59108F = 8 LEDs
VCC
SDA
SCL
RESET
R
E
X
T
VLED
VCC
SDA
SCL
A0
A1
A2
A3
RESET
REXT
GND
OUT0
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
Address: 00h
REXT is used to set the current for the TLC59108.
All channels will have the same current based on REXT.
VLED
R0 R1 R2 R3 R4 R5 R6 R7
VCC
SDA
SCL
RESET
VCC
SDA
SCL
A0
A1
A2
A3
RESET
GND
OUT0
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
Address: 00h
Figure 20. TLC59108 One Driver
R0 through R7 are used to set the current for each channe. l.
Changing the values of R0-R7 allows the user to use different
colored (forward voltage) LEDs on a single TLC59108F.
Figure 21. TLC59108F One Driver
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