LP8866S-Q1: PWM, and Current data

Hi All, 

Is there any update for this? 

Thank you

Hi Ully,

Our expert is OoO today and will reply you later.

BR, Jared

HI, Ully

Our device has a slope function which will not change it directly.

Hi Zhiqian,

So so this is normal right?

What if we update the software to make the current directly to the maximum one? will it affect the led driver?

Hi, Ully

Pls check with the brightness path.

If you change current directly, it will not go through slope function and will not affect the LED driver.

Hi Zhiqian

okay noted, please confirm (in my understanding) :

1. Its normal for the Input PWM and Current start from the lowest value first  then to the maximum value, because it has the slope function
2. If we set the software to make the PWM and current directly to the maximum value that's mean that we will skip the slope function? And its till okay and will not affect the LED Driver.

correct me if i am wrong

Thank you

Hi, Ully

if you change the brightness register or use PWM input, it will control by slope.

But for current register change, no slope will affect.

Hi Zhiqian

So what this means is, if a change occurs in the PWM, it will be controlled by the Slope Brightness, but if only the current changes and the PWM input remains the same then the slope function doesn't work right?

And, For the Sloper function, when this function will be enable? Because in our LED DRIVER log result, the slope only happen during the Power BAT OFF&ON, but not happen in Backlight OFF&ON? But in my understanding, if we enable the sloper function it should be applied in every PWM change condition right? (Correct me if I am wrong)

Hi, Ully

In the diagram, the current can also be changed by brightness control in analog or hybrid dimming mode. It will also trigger slope.

Slope will be active when input duty cycle changed.

Hi Zhiqian 

okay got it, By the way can we see the register data when the Slope works? because right now i am checking in the data using UART. I Mean how to check that the slope is work?, 

and back to my first question,

When we turn on the ACC and BAT Power, the Current is not directly to the maximum value right, but start from the lowest value, 

and you said it because the LED Driver has a slope function, so

1. Why it only happen from the BAT Power ON, Is this condition only happen in the maximum condition?

2. Why when i only turn OFF and Turn On the BACKLIGHT, the above conditions do not occur, even though if we turn off the backlight, the PWM will also change to 0, and when it is turned on again, the value will be the same as the value before it was turned off. 

...

Hi, Ullty

could you confirm that during your turn off of the backlight, the device is powered off? Could you pls share any waveform about your concern?

waveform can show what happened to the device easily. And how do you get the current in your image?

Hi Zhiqian, 

During the BACKLIGHT OFF/ON , the device is still Turn ON, only the Backlight is OFF, 
For the picture its from the UART read results, I am using UART to verify the I2C communication, to find out whether the data sent corresponds to reality

Hi, Ully

Understand, as you mentioned that, the current increased from during the test, it is better to catch the waveform to have a double check. It will be clear for the action of the device.

Hi Zhiqian

okay noted, i will try to get the waveform during the BAT Power OFF/ON, and BACKLIGHT OFF/ON.

By the way about the slope, so is it not possible to check that the slope is work by the UART data?

Hi Ully,

Our expert is out of office and will give you feedback when comes back.

BR

Patrick

Hi Zhiqian,

This is the waveform result during:

CH1 : VOUT

CH2 : VDD

CH3 Output Current

1. BAT POWER OFF/ON

During BAT POWER OFF/ON, all of the device will turn off

2. Only BACKLIGHT OFF/ON

During BACKLIGHT OFF/ON, only the current will go down, the other parameter still turn On

Back to my question, and your explanation (the UART Data not directly go to max because we have sloper function)  

For the Sloper function, when this function will be enable? Because in our LED DRIVER log result, the slope only happen during the Power BAT OFF&ON, but not happen in Backlight OFF&ON? But in my understanding, if we enable the sloper function it should be applied in every change condition right? (Correct me if I am wrong)

Hi Ully,

Noted, we will give you feedback asap.

Hi, Ully

Pls check with below register about slope function.

In the waveform, the BACKLIGHT OFF/ON can also see the slope about 200ms. So could you clarify about the slope time you find in UART?

Hi Zhiqian

I have check the time, by oscilloscope, the rise time is 203ms, but in the UART, the time is more than 200mS. 

HI, Ully

So depending on the waveform the rise time is 200ms, it matches the register setting.