TLC5940 Datasheet, PDF (11/29 Pages) Texas Instruments – 16 CHANNEL LED DRIVER WITH DOT CORRECTION AND GRAYSCALE PWM CONTROL

TLC5940
www.ti.com
SLVS515A – DECEMBER 2004 – REVISED AUGUST 2005
PRINCIPLES OF OPERATION
SERIAL INTERFACE
The TLC5940 includes 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 rising edge of XLAT latches
the serial data to the internal registers. All data are clocked in with the MSB first. Multiple TLC5940 devices can
be cascaded by connecting the SOUT pin of one device with the SIN pin of the following device. The SOUT pin
can also be connected to the controller to receive status information from TLC5940. The serial data format is
96-bit or 192-bit wide, depending on programming mode of the device.
Vcc
VPRG
DC Mode Data
Input Cycle
GS Mode Data
Input Cycle
DC Mode Data
Input Cycle
XLAT
t_h3
t_su3
t_h3
SIN
SCLK
DC n
MSB
1
DC n
LSB
t_h2
96
GS
MSB
t_su2
1
GS
LSB
t_h2
192
193
DC n+1 DC n+1
MSB MSB−1
t_su2
1
2
SOUT
DC n
MSB
DC n
LSB
DC
MSB
X
X
GS
MSB
SID
MSB
X
Figure 6. Serial Data Input Timing Chart
ERROR INFORMATION OUTPUT
The open-drain output XERR is used to report both of the TLC5940 error flags, TEF and LOD. During normal
operating conditions, the internal transistor connected to the XERR pin is turned off. The voltage on XERR is
pulled up to V_CC through an external pullup resistor. If TEF or LOD is detected, the internal transistor is turned
on, and XERR is pulled to GND. Since XERR is an open-drain output, multiple ICs can be OR'ed together and
pulled up to V_CC with a single pullup resistor. This reduces the number of signals needed to report a system error
(see Figure 14).
To differentiate LOD and TEF signal from XERR pin, LOD can be masked out with BLANK = HIGH.
Table 1. XERR Truth Table
ERROR CONDITION
TEMPERATURE
OUTn VOLTAGE
T_J < T_(TEF)
T_J > T_(TEF)
T_J < T_(TEF)
T_J > T_(TEF)
Don't Care
Don't Care
OUTn > V_(LED)
OUTn < V_(LED)
OUTn > V_(LED)
OUTn < V_(LED)
ERROR INFORMATION
TEF
LOD
L
X
H
X
L
L
L
H
H
L
H
H
SIGNALS
BLANK
XERR
H
H
L
H
L
L
L
L
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