Packing those features into such a small chip has created a device that has got some nasty traps that are not described in the datasheet or hard to understand and so it is easy for beginning hardware hackers to either fry a couple of chips or just give up in frustration. If you are looking into using this chip, check out my experiences after the break. If you do this, you must make sure that the LED circuits are never powered if the chip is unpowered. You can enforce this with a high-side driver chip.
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Dot Correction — 6 bit 64 Steps? Controlled In-Rush Current? LED Signboards? Each channel has an individually adjustable step grayscale PWM brightness control and a step constant-current sink dot correction. Both grayscale control and dot correction are accessible via a serial interface. A single external resistor sets the maximum current value of all 16 channels.
The TLC features two error information circuits. The thermal error flag TEF indicates an overtemperature condition. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.
These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied. Exposure to absolute maximum rated conditions for extended periods may affect device reliability. See application report SLMA for further information.
No internal connection 6 TLC www. RHB NO. I GS counter is also reset. It is important to connect both pins to supply voltage to ensure proper operation of the device. I Input mode-change pin. O Error output. XERR is an open-drain terminal. Data latch. Note that the internal connections are switched by MODE. Input and Output Equivalent Circuits 8 www. Reference Resistor? W Power Dissipation Rate? Output Current? Free-Air Temperature? Output Voltage? V Figure 5. Only 3 pins are needed to input data into the device.
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. The serial data format is bit or bit wide, depending on programming mode of the device.
During normal operating conditions, the internal transistor connected to the XERR pin is turned off. This reduces the number of signals needed to report a system error see Figure Table 1. This circuit reports an error if any one of the 16 LEDs is open or disconnected from the circuit. The LOD circuit trips when the following two conditions are met simultaneously: 1. Note: the voltage at each OUTn is sampled 1? These circuits can be found in the constant-current driver block of the device see functional block diagram.
The delay works by switch on and switch off of each output channel. These delays prevent large inrush currents and switching noise which reduces the bypass capacitors when the outputs turn on.
The grayscale counter is also reset. Table 2. The maximum channel current is equivalent to the current flowing through R IREF multiplied by a factor of This is also called dot correction. Each of the 16 channels can be programmed with a 6-bit word. The complete dot correction data format consists of 16 x 6-bit words, which forms a bit wide serial data packet. The channel data is put one after another. All data is clocked in with MSB first.
Figure 7 shows the DC data format. The internal input shift register is then set to bit width. After all serial data are clocked in, a rising edge of XLAT is used to latch the data into the dot correction register.
Figure 8 shows the dc data input timing chart. The complete grayscale data format consists of 16 x 12 bit words, which forms a bit wide data packet see Figure 9. The data packet must be clocked in with the MSB first. The device switches the input shift register to bit width. After all data is clocked in, a rising edge of the XLAT signal latches the data into the grayscale register see Figure All GS data in the input shift register is replaced with status information data SID after latching into the grayscale register.
The status information data packet is bits wide. Bits — contain the LOD status of each channel. Bit contains the TEF status. Bits 72 — contain the data of the dot-correction register. The remaining bits are reserved. The complete status information data packet is shown in Figure All OUTn with grayscale values equal to counter values are switched off. The maximum number of cascading TLC devices depends on the application system and is in the range of 40 devices.
Cascading Devices 17 www. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
Samples may or may not be available. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
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Tutorial – Arduino and the TLC5940 PWM LED Driver IC
Our reason for doing this is to demonstrate another, easier way of driving many LEDs — and also servos. It really is a convenient part, allowing you to adjust the brightness of sixteen individual LEDs via PWM pulse-width modulation — and you can also daisy-chain more than one TLC to control even more. You can use it to experiment with various functions and get an idea of what is possible. The purpose of the resistor is to control the amount of current that can flow through the LEDs. You should be presented with output similar to what is shown in the following video : Controlling the TLC Now that the circuit works, how do we control the TLC? First, the mandatory functions — include the library at the start of the sketch with: include "Tlc