TLC5947_17 Datasheet, PDF (18/33 Pages) Texas Instruments – 24-Channel, 12-Bit PWM LED Driver With Internal Oscillator

TLC5947
SBVS114B – JULY 2008 – REVISED JANUARY 2015
9 Application and Implementation
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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
The device is a 24-channel, constant sink current, LED driver. This device can be connected in series to drive
many LED lamps with only a few controller ports. Output current control data and PWM control data can be
written from the SIN input terminal. The PWM timing reference clock can be supplied from the internal oscillation.
9.2 Typical Application
V_LED
V_LED
V_LED
V_LED
¼
¼
¼
Controller
DATA
SCLK
XLAT
BLANK
¼
¼
¼
¼
¼ _OUT0
OUT23
SIN
SOUT
SCLK
V_CC
XLAT TLC5947
BLANK ^IC1
VCC
¼
¼
¼ _OUT0
OUT23
SIN
SOUT
SCLK
V_CC
XLAT TLC5947
BLANK ^ICn
VCC
R_IREF
IREF
GND
R_IREF
IREF
GND
3
Figure 23. Typical Application Circuit (Multiple Daisy Chained TLC5947s)
9.2.1 Design Requirements
For this design example, use Table 2 as the input parameters.
Table 2. Design Parameters
DESIGN PARAMETER
VCC input voltage range
LED lamp (V_LED) input voltage range
SIN, SCLK, LAT, and BLANK voltage range
EXAMPLE VALUE
3 V to 5.5 V
Maximum LED forward voltage (V_F) + IC knee voltage
Low level = GND, High level = VCC
9.2.2 Detailed Design Procedure
9.2.2.1 Define Basic Parameters
To begin the design process, a few parameters must be decided as following:
• Maximum output constant-current value for each color LED lamp
• Maximum LED forward voltage (V_F)
• Are auto display function used
18
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