TLC5958 Datasheet, PDF (16/28 Pages) Texas Instruments – TLC5958 48-Channel, 16-Bit ES-PWM LED Driver with Pre-Charge FET, LED Open Detection and Display Data Memory Support 32-Multiplexing

TLC5958
SLVSCE7A – MAY 2014 – REVISED SEPTEMBER 2014
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10.3 Device Functional Modes
After power on, all OUTXn of the TLC5958 are turned off. All the internal counters and function control registers
(FC1/FC2) are initialized. The following list is a brief summary of the sequence to operate the TLC5958, to give
users a general idea how the device works. After that, the function block related to each step is detailed in the
following sections.
1. According to required LED current, choose BC & CC code, select the current programming resistor RIREF.
2. Send WRTFC command to set FC1/2 register value if the default value need be changed.
3. Write GS data of all lines (max 32 lines) into one of the two memory BANKs.
4. Send Vsync command, the BANK with the GS data written just now will be displayed.
5. Input GCLK continuously, 257GCLK (or 513GCLK) as a segment. Between the interval of two segments,
supply voltage should be switched from one line to next line accordingly.
6. During the same period of step 5, GS data for next frame should be written into another BANK.
7. When the time of one frame ends, Vsync command should be input to swap the purpose of the two BANKs.
Repeat step 5 through 7.
10.3.1 Brightness Control (BC) Function
The TLC5958 is able to adjust the output current of all constant-current outputs simultaneously. This function is
called global brightness control (BC). The global BC for all outputs is programmed with a 3-bit word, thus all
output currents can be adjusted in 8 steps from 12.9% to 100% for a given current-programming resistor, R_IREF
(See Table 2).
BC data can be set via the serial interface. When the BC data changes, the output current also changes
immediately. When the device is powered on, the BC data in the function control (FC) register FC1 is set to 4h
as the initial value.
10.3.2 Color Brightness Control (CC) Function
The TLC5958 is able to adjust the output current of each of the three color groups OUTR0-OUTR15, OUTG0-
OUTG15, and OUTB0-OUTB15 separately. This function is called color brightness control (CC). For each color,
it has 9-bit data latch CCR,CCG, or CCB in FC1 register . Thus, all color group output currents can be adjusted
in 512 steps from 0% to 100% of the maximum output current, I_OLCMax. (See the next section for more detail
about I_OLCMax). The CC data are entered via the serial interface. When the CC data change, the output current
also changes immediately.
When the IC is powered on, the CC data are set to ‘100h’. Equation 1 calculates the actual output current.
Iout(mA) = IOLCMax(mA) × ( CCR/511d or CCG/511d or CCB/511d)
(1)
Where:
I_OLCMax = the maximum channel current for each channel, determined by BC data and R_IREF (See Equation 2)
CCR/G/B = the color brightness control value for each color group in the FC1 register (000h to 1FFh)
Table 1 shows the CC data versus the constant-current against I_OLCMax.
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