TLC59116F_15 Datasheet, PDF (24/38 Pages) Texas Instruments – 16-Channel Fast-Mode Plus I2C Bus LED Driver

TLC59116F
SCLS714C – MARCH 2009 – REVISED SEPTEMBER 2015
9.2 Typical Application
This application example provides guidance on how to set the LED current using the TLC59116F.
V_LED
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3.3V or 5V
R_SET
SCL
SDA
RESET
Microcontroller
SCL
SDA
RESET
A0-A3
VDD
OUT15
OUT14
OUT13
TLC59116F
OUT1
OUT0
GND
Figure 20. Typical Application Schematic
9.2.1 Design Requirements
For this design example, use the following as the input parameters.
Table 11. Design Parameters
V_LED
V_F
I_LED
R_ON
DESIGN PARAMETER
Supply voltage that powers the LED
Forward voltage across the LED
Current flowing through the LED
Resistance across open-drain output
EXAMPLE VALUE
5V
3V
6 mA
1.5 Ω
9.2.2 Detailed Design Procedure
In the LED current path, there are three voltage drops that must be considered:
• Drop across the series resistor (V_RSET)
• Drop across the LED (V_F)
• Drop across the open-drain output channel (V_O)
The drop across the LED is defined above as VF = 3V. The drop across the open-drain output is calculated as
R_ON x I_LED (1.5 Ω × 0.006 A = 0.009 V). The remaining voltage must be across the series resistor:
5 V = 3 V + 0.009 V + V_RSET
• V_RSET = 1.991 V
(4)
After calculating V_RSET, we can calculate R_SET:
V_RSET = I_LED × R_SET
• 1.991V = 0.006 mA × R_SET
• R_SET = 332 Ω
(5)
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