LP5813 datasheet(25/60 Pages) TI

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in Figure 9-20. Only AEU2 is enabled in the pattern, so that the brightness of APU1 uses the PWM1 value of

AEU2, and the brightness of APU2 uses PWM5 value of AEU2.

PWM5

AEU

APU2

APU1

PWM1

Figure 9-20. APU example

9.3.6 Protections and Diagnostics

9.3.6.1 Overvoltage Protection

The boost of LP5813 has an output overvoltage protection (OVP) to protect the device. When the output voltage

is above 5.7 V, the boost stops switching. Once the output voltage falls 0.1 V below the OVP threshold, the boost

resumes operating again.

9.3.6.2 Output Short-to-Ground Protection

The boost of LP5813 starts to limit the boost current when the boost output voltage is below 1.8 V. The lower the

boost output voltage reaches, the smaller the output current decreases. When the VOUT pin is short to ground

and the boost output voltage is less than 0.4 V, the output current is limited to approximately 350 mA. Once the

short circuit is released, the LP5813 goes through the soft start-up again to the regulated output voltage.

9.3.6.3 LED Open Detections

The LP5813 integrates LED open detection (LOD) for the fault caused by any open LED. The threshold for LOD

is 90 mV when max current is set as 25.5 mA, and 180 mV when max current is set as 51 mA. To have enough

detection time, LOD can only be performed when the PWM setting of this LED is above 25. If the voltage on the

cathode of this LED is lower than the LOD threshold in continuously 3 cycles, LED open of this LED is reported

to the corresponding LOD_status register.

The LOD flags can be cleared by writing 1h to 'lod_clear' bit in Fault_Clear register. If the LED open status is

removed, the related 'lod_status' bit is set to 0 automatically.

The 'lod_action' bit in Dev_config_12 register can determine the action once open fault is detected. When the

'lod_action' bit is set to 1h, the dot where LED open happens is turned off to avoid any unpredictable issue.

When the 'lod_action' bit is 0, no additional action is taken after LOD is detected. LED open fault detection and

action is only executed in NORMAL state.

9.3.6.4 LED Short Detections

The LP5813 integrates LED short detection (LSD) for the fault caused by any short LED. The threshold of LSD is

able to configure from (0.35 × VOUT) V to (0.65 × VOUT) V by configuring lsd_threshold in Dev_config_12 register.

To have enough detection time, LSD can only be performed when the PWM setting of this LED is above 25. If

the voltage on the cathode of this LED is higher than the LSD threshold in continuously 3 cycles, LED short of

this LED is reported to the corresponding LSD_status register.

The LSD flags can be cleared by writing 1h to lsd_clear in Fault_CLR register. If the LED short status is

removed, the related lsd_status bit is set to 0 automatically.

The 'lsd_action' bit in Dev_config_12 register can determine the reaction once open fault is detected. When the

'lsd_action' bit is set to 1h, all LEDs are turned off which is called one fails all fail (OFAF) action, to prevent

potential damage caused by the short issue. The device enters to STANDBY state after sending 'lsd_clear'

command. When the 'lsd_action' bit is 0, no additional action is taken after LSD is detected. LSD detecion is only

executed in NORMAL state.

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LP5813

SNVSC74 – SEPTEMBER 2023

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