LP5813 datasheet(22/60 Pages) TI

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Table 9-3. Dot Current (DC) bits setting (continued)

8-bits Dot Current (DC) Register

Ratio of IOUT_MAX

Binary

Decimal

---

1000 0000 (default)

128 (default)

50.2% (default)

---

1111 1101

253

99.2%

1111 1110

254

99.6%

1111 1111

255

100%

By configuring the MC and DC, the peak current of each current sink can be calculated as Equation 6:

IOUT mA =IOUT_max×DC255

(6)

The average current of each LED in TCM drive mode and mix drive mode is shown as Equation 7:

IAVE mA =IOUTN×DC255×DPWM

(7)

• N is the total scan number setting.

• DPWM is the PWM duty.

9.3.4 PWM Dimming

The LP5813 supports 8-bit PWM dimming with 24 kHz or 12 kHz frequency, which is configured by 'PWM_Fre'

bit in Dev_config_1 register. An internal 6 MHz oscillator is used to generate the PWM clock. SYNC pin can be

configured as PWM clock input or output by configure 'vsync_out_en' bit in Dev_Config_11 register. If multiple

LP5813 are used in the system with autonomous animation engine control, all devices can refer the same

clock signal, which comes from one of LP5813 or external controller, to avoid animation mismatch in long time

operation.

Each LED can be configured into 3 different PWM alignment phases: Forward, Middle, and Backward. The

alignment phase of each LED is set by 'phase_align' bits in Dev_Config_7 to Dev_Config_10 registers. By

turning on the LEDs in different phase, the peak current load from boost or the system power supply is greatly

decreased. The input current ripple and ceramic-capacitor audible ringing can also be reduced. Figure 9-14

shows the PWM alignment phases. In the forward alignment, the rising edge of PWM pulse is fixed at the

beginning of PWM period. In the middle alignment, the middle point of PWM pulse is fixed at the middle of PWM

period, while the pulse spreads to both directions. In the backward alignment, the falling edge of PWM pulse is

fixed at the end of PWM period.

Forward

Alignment

Middle

Alignment

Backward

Alignment

PWM Period

1/fPWM

Half PWM Period

1/2fPWM

Figure 9-14. PWM Alignment Scheme

LP5813

SNVSC74 – SEPTEMBER 2023

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