LP5860 datasheet(17/71 Pages) TI

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Table 8-4. Data Refresh Mode (continued)

MODE TYPE

PWM RESOLUTION

PWM OUTPUT

EXTERNAL VSYNC

Mode 2

8 bits

Data update by frame

Yes

Mode 3

16 bits

8.3.5 Full Addressable SRAM

SRAM is implemented inside the LP5861T device to support data writing and reading at the same time.

Although data refresh mechanisms are not the same for Mode 1 and Mode 2 and 3, the data writing and

reading follow the same method. Uses can update partial of the SRAM data only or the whole SRAM page

simultaneously. The LP5861T supports auto-increment function to minimize data traffic and increase data

transfer efficiency.

Please note that 16-bit PWM (Mode 3) and 8-bit PWM (Mode 1 and Mode 2) are assigned with different SRAM

addresses.

8.3.6 Protections and Diagnostics

LED Open Detection

The LP5861T includes LED open detection (LOD) for the fault caused by any opened LED dot. The threshold

for LED open is 0.25-V typical. LED open detection is only performed when PWM ≥ 25 (Mode 1 and Mode

2) or PWM ≥ 6400 (Mode 3) and voltage on CSn is detected lower than open threshold for continuously 4

sub-periods.

Figure 8-8 shows the detection circuit of LOD function. When open fault is detected, 'Global_LOD' bit in

Fault_state register is set to 1 and detailed fault state for each LED is also monitored in register Dot_lodx

(x = 0, 1, … , 2). All open fault indicator bits can be cleared by setting LOD_clear = 0Fh after the open condition

is removed.

LOD removal function can be enabled by setting 'LOD_removal' bit in Dev_config2 register to 1. This function

turns off the current sink of the open channel when scanning to the line where the opened LED is included.

CS17

–

CS1

LODVTH

CS0

Channel_lodxx Register

Channel

Control

LOD data set to

Global_LOD Bit

–

Channel

Control

–

Channel

Control

GND

Lower than threshold for

con nuously 4 mes

Comparing with

open threshold

0.25 V

LODVTH

Figure 8-8. LOD Circuits

LED Short Detection

The LP5861T includes LED short detection (LSD) for the fault caused by any shorted LED. Threshold for

channel short is (VLED – 1) V typical. LED short detection only performed when PWM ≥ 25 (Mode 1 and Mode

2) or PWM ≥ 6400 (Mode 3) and voltage on CSn is detected higher than short threshold for continuously 4

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LP5861T

SNVSCE4 – MAY 2023

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