TLC5947_17 Datasheet, PDF (20/33 Pages) Texas Instruments – 24-Channel, 12-Bit PWM LED Driver With Internal Oscillator

TLC5947
SBVS114B – JULY 2008 – REVISED JANUARY 2015
www.ti.com
10 Power Supply Recommendations
The VCC power supply voltage should be decoupled by placing a 0.1-µF ceramic capacitor close to the VCC pin
and GND plane. Depending on the panel size, several electrolytic capacitors must be placed on the board
equally distributed to get a well regulated LED supply voltage (V_LED). The V_LED voltage ripple must be less than
5% of its nominal value. Furthermore, the V_LED must be set to the voltage calculated by Equation 3:
V_LED > V_F + 0.4 V (10-mA constant-current example)
where
• V_F = maximum forward voltage of all LEDs.
(3)
11 Layout
11.1 Layout Guidelines
• Place the decoupling capacitor near the VCC pin and GND plane.
• Place the current programming resistor R_IREF close to the IREF pin and the IREFGND pin.
• Route the GND pattern as widely as possible for large GND currents.
• The routing wire between the LED cathode side and the device OUTXn pin must be as short and straight as
possible to reduce wire inductance.
• When several ICs are chained, symmetric placements are recommended.
11.2 Layout Example
GND
BLANK
SCLK
SIN
OUT0
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
OUT8
OUT9
OUT10
OUT11
GND
VCC
GND
1
32
2
31
3
30
4
29
5
28
6
Thermal
27
Pad
7
26
8
25
9
24
10
Via to
Heatsink
23
11
Layer
22
12
21
13
20
14
19
15
18
16
17
VCC
IREF
XLAT
SOUT
OUT23
OUT22
OUT21
OUT20
OUT19
OUT18
OUT17
OUT16
OUT15
OUT14
OUT13
OUT12
Figure 26. Layout Schematic
20
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