LP8863-Q1: Dimming ratio and dimming resolution

user1572638

Prodigy 20 points

Part Number: LP8863-Q1

If fPWM_OUT = 1221Hz is set, is the following recognition OK?

・ Dimming ratio is 4000: 1 because tPWM_OUT = 200ns and 4095 (= 819us / 200ns).

・ Dimming resolution is 2 ^ 14 because it is 16380 (= 819us / 50ns) from 50ns (internal 20-MHz oscillator).

over 4 years ago

0 Frank Qiu over 4 years ago

TI__Genius 15776 points

Hi,

You can reference the below link to know it.

https://e2e.ti.com/support/power-management/f/196/t/808858?tisearch=e2e-quicksearch&keymatch=dimming

0 user1572638 over 4 years ago in reply to Frank Qiu

Prodigy 20 points

I confirmed the link. However, since it is still not resolved, let me ask a question again.
I want to dim using only the DISPLAY_BRT [15: 0] register. DIMMING_MODE [1: 0] register is 0h = PWM Mode.
All LEDx_CURRENT [11: 0] registers are fixed to FFFh.
All Output connected together to drive one string.
Set fPWM_OUT = 1221Hz.
I want to know how many bits the dimming resolution is.
I don't know the difference between Dimming ratio in LP8863-Q1 datasheet page 9 and PWM DIMMING RESOLUTION (bit) in page 25.
Is the valid range of the DISPLAY_BRT [15: 0] register from 0008h to FFF8h? (2^12 4000: 0)
Or
Is the valid range of the DISPLAY_BRT [15: 0] register from 0004h to FFFCh? (2^14 16000: 0)

0 Frank Qiu over 4 years ago in reply to user1572638

TI__Genius 15776 points

in pwm mode.

When you set fPWM_OUT = 1221Hz, the resolution is 14 bit that means DISPLAY_BRT [15: 0] register's valid range from

0000 0000 0000 01xxb to

1111 1111 1111 11xxb

bite0 and bite1 have no effect on dimming.

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LP8863-Q1: Dimming ratio and dimming resolution