TLC5957 Datasheet, PDF (13/25 Pages) Texas Instruments – TLC5957 48-Channel, 16-Bit ES-PWM LED Driver with Pre-Charge FET, LED OPEN Detection and Caterpillar Cancelling

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TLC5957
SLVSCQ4 – OCTOBER 2014
9.3 Device Functional Modes
After power on, all OUTXn of TLC5957 are turned off. All the internal counters and function control registers are
initialized. Below is a brief summary of the sequence to operate TLC5957, just give users a general idea how this
part works. After that, the function block related to each step will be detailed in following sections.
1. According to required LED current, choose BC and CC code, select the current programming resistor R_IREF.
2. Send WRTFC command to set FC register value if the default value need be changed.
3. Write GS data of line 1 into GS data latch. Using LATGS command for the last group of 48bit GS data
loading, the GS data written just now will be displayed.
4. Input GCLK continuously, 2^N GCLK (N>=9) as a segment. Between the interval of two segments, supply
voltage should be switched from one line to next line accordingly.
5. During the same period of step4, GS data for next line should be written into GS data latch. Using LATGS
command for the last group of 48bit GS data loading.
6. Repeat step 4-5 until it comes to the last line for a multiplexing panel. Input 2^N GCLK (N>=9) as a segment,
at the same time, GS data for 1^st line should be written into GS data latch. Using LINERESET command for
the last group of 48bit GS data loading.
Repeat step 4 through 6.
9.3.1 Brightness Control (BC) Function
The TLC5957 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% (See Table 2) for a given current programming
resistor(R_IREF)
BC data can be set via the serial interface. When the BC data change, the output current also changes
immediately. When the device is powered on, the BC data in the function control (FC) register is set to 4h as the
initial value.
9.3.2 Color Control (CC) Function
The TLC5957 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 FC 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 next section for more details 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) = I_OLCMax(mA) × ( CCR/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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