TLC5940_15 Datasheet, PDF (13/38 Pages) Texas Instruments – 16-Channel LED Driver

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8 Detailed Description
TLC5940
SLVS515D – DECEMBER 2004 – REVISED NOVEMBER 2015
8.1 Overview
The TLC5940 is a 16-channel constant current sink driver. Each channel has an individually-adjustable, 4096-
step, pulse width modulation (PWM), grayscale (GS) brightness control, and a 64-step dot correction brightness
control. GS data and DC data are input via a serial interface port. The dot correction data is stored in an
integrated EEPROM. The TLC5940 has a 120-mA current capability. The maximum current value of all channels
is determined by an external resistor. The TLC5940 has a LED open detection (LOD) function that indicates a
broken or disconnected LED at an output terminal and a thermal error flag (TEF) indicates an overtemperature
condition.
8.2 Functional Block Diagram
VCC GND
SCLK
SIN
XLAT
DCPRG
IREF
Max. OUTn ^{VREF =1.24 V}
Current
GSCLK
BLANK
GS Counter
CNT
Status ⁰
96
Information: 192
LOD,
TED,
DC DATA
96
191
LED Open
Detection
(LOD)
VPRG
10
0
VPRG
CNT
10
GS Register
0
11
DCPRG
1
DC Register
0
50
12−Bit Grayscale
PWM Control
6−Bit Dot
Correction
Input
Shift
Register
192
95
96
10
VPRG
96
0 DC EEPROM 5
VPRG
LED Open Detection
CNT
GS Register
12
23
DC Register
6
11
DCPRG
1
0
12−Bit Grayscale
PWM Control
6−Bit Dot
Correction
6 DC EEPROM11
VPRG
LED Open Detection
Temperature
Error Flag
(TEF)
Blank
10
XERR
Input
Shift
Register
191
CNT
GS Register
180
191
DCPRG
1
DC Register
90
95 0
12−Bit Grayscale
PWM Control
6−Bit Dot
Correction
DC EEPROM
90
95
LED Open Detection
SOUT
VPRG
Constant Current
Driver
Delay
x0
Constant Current
Driver
Delay
x1
Constant Current
Driver
Delay
x15
OUT0
OUT1
OUT15
8.3 Feature Description
8.3.1 Serial Interface
The TLC5940 has a flexible serial interface, which can be connected to microcontrollers or digital signal
processors in various ways. Only 3 pins are needed to input data into the device. The rising edge of SCLK signal
shifts the data from the SIN pin to the internal register. After all data is clocked in, a high-level pulse of XLAT
signal latches the serial data to the internal registers. The internal registers are level-triggered latches of XLAT
signal. All data are clocked in with the MSB first. The length of serial data is 96 bit or 192 bit, depending on the
programming mode. Grayscale data and dot correction data can be entered during a grayscale cycle. Although
new grayscale data can be clocked in during a grayscale cycle, the XLAT signal should only latch the grayscale
data at the end of the grayscale cycle. Latching in new grayscale data immediately overwrites the existing
grayscale data. Figure 11 shows the timing chart. More than two TLC5940s can be connected in series by
connecting an SOUT pin from one device to the SIN pin of the next device. An example of cascading two
TLC5940s is shown in Figure 12 and the timing chart is shown in Figure 13. The SOUT pin can also be
connected to the controller to receive status information from TLC5940 as shown in Figure 22.
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