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LED Drivers/LCD Bias
LED Drivers/LCD Bias Forum
TLC5916 - Output default turnon state?
The TLC5916 outputs will power up to an OFF state. Since the outputs are SINK drivers, they will not pull high, the will just not pull low. As a result, the output pins will go to VLED.
If you need a simple way to turn them on without a microcontoller, please see this application note:
I was never use TLC5916. From datasheet I haven't found precise info in which way LED current is controlled.
I mean by internal PWM or by real analog current control.
With best regards, Marek
There are several ways to control the LED current on the TLC5916. There is not an internal PWM.
Setting REXT is the global setting which controls the LED current for all outputs together. This is strictly an analog setting.
The Configuration Code sets the Voltage Gain and Current Multiplier. These together change the Analog current as a ratio of the REXT programmed current. This can range from 8.3% to 99.2% of the programmed REXT value. This is strictly an analog reduction in current.
There are also ways to use PWM dimming. The simplest way is with the OE pin. When OE is high, all outputs are OFF. When OE is low, all outputs are ON. Setting a frequency and duty cycle on the OE pin can be used for PWM dimming. Additionally, the TLC5916 can operate up to30MHz through the serial interface. You can write data to the TLC5916 at different rates to impact dimming. For example, writing a channel ON for 50% of the time and OFF for 50% of the time would essentially be 50% brightness through PWM dimming.
If this is not clear, let me know.
I just understand to control TCL5917 we just control OE pin. If we set low OE pin all the leds will be on with maximum PWM. If control pwm and duty cyle of OE pin we can control it in PWM mode. By the way what do you mean by "The Configuration Code sets the Voltage Gain and Current Multiplier" where we set it?
The Configuration code is discussed on page 24 of the TLC5917 datasheet. Basically, it is an internal register that allows the user to set the current to a percentage of the REXT programmed current. To enter data to the register, the user must enter the "Special Mode". This mode allows writing to the configuration register instead of to the output register. Switching between operation modes (normal and special) is discussed in pages 20-21. The default of the configuration code register is all 255 (0xFF). This default sets the gain to 99.2% (full scale). This means that when the current is programmed to 100mA, the actual current will be 99.2% of 100mA (or 99.2mA). Figure 22 shows the relationship between the bit programming and the resulting current gain. If all bits are set to 0 (0x00) then the resulting multiplier is 8.3% (8.3mA if 100mA is programmed by the REXT).
Let me know if this helps.
Project description: Driving LED current by using TLC5917 IC.
(SDI,CLOCK,OE,LE) Input is given from PIC microcontroller. Driver IC is working in normal mode. We send a switch special mode data (CLK,OE,LE as per datasheet), didn't any changes in LED brightness.
Kindly send a any suggestion?
Can you include information on the procedure you are using? A waveform would be excellent to evaluate. Once in special mode normal writing will go to the configuration code and the brightness should change immediately.
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