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| TLC5973 Datasheet, PDF (26/34 Pages) Texas Instruments – TLC5973 3-Channel, 12-Bit, PWM Constant-Current LED Driver with Single-Wire Interface (EasySet) | |||
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TLC5973
SBVS225B â MARCH 2013 â REVISED MAY 2014
www.ti.com
9.2.3 Internal Shunt Regulator Mode
This application uses the shunt regulator. The device VCC and LED lamp anode voltage are supplied from the
same power supply. At least two LED lamps are connected in series.
VLED
Power
Supply
GND
RVCC
CVCC
RVCC
CVCC
+5 V
Controller
RIREF
GND
IREF
Device
SDI
VCC
OUT0
OUT1
OUT2
SDO
Optional
RIREF
GND
IREF
Device
SDI
VCC
OUT0
OUT1
OUT2
SDO
Optional
Figure 26. Internal Shunt Regulator Mode Typical Application Circuit
9.2.3.1 Design Requirements
DESIGN PARAMETER
Input voltage range for VLED
SDI voltage range
SDI data transfer rate
Table 6. Design Parameters
EXAMPLE VALUE
6 V to 24 V
Low level = GND, high level = 5.0 V to 6.0 V
100 kbps to 3 Mbps
9.2.3.2 Detailed Design Procedure
The TLC5973 internally integrates a shunt regulator to regulate VCC voltage. Refer to Figure 27 for an application
circuit that uses the internal shunt regulator through a resistor, RVCC. The recommended RVCC value can be
calculated by Equation 2.
VLED (V) - 5.9 V
13 mA
< RVCC <
VLED (V) - 5.9 V
11 mA
(2)
VLED
Power
Supply
GND
RVCC
CVCC
(0.1 mF)
RVCC
CVCC
(0.1 mF)
+5 V
Controller
RIREF
GND
VCC
IREF
OUT0
OUT1
1st Device
OUT2
SDI
SDO
RIREF
GND
VCC
IREF
OUT0
OUT1
2nd Device
OUT2
SDI
SDO
Optional
Figure 27. Internal Shunt Regulator Mode Application Circuit
26
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