LP5813 datasheet(16/60 Pages) TI

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OUT0

OUT1

OUT2

OUT3

Time

PWM

One frame, Tframe

PWM

Acting as scan switch

Acting as current sink

VOUT

Scan order 0

Scan order 1

Scan order 2

Scan order 3

Tblank

Tsub

Tdim

De-ghosting

LOD/LSD

Red LED

Green LED

Blue LED

* Scan orders and numbers are configurable

Figure 9-3. Time-cross-multiplexing (TCM) Scheme

Figure 9-3 shows the simplified TCM scheme timing diagram of the four outputs. A complete display frame

includes 4 sub-periods. Each sub-period contains dimming period and blank time period. In switching period, 1

output is selected as switch and the other 3 OUTs are selected as current sinks. Blank time is applied between

two adjacent switching periods for ghosting elimination.

One sub-period cycle time Tsub is calculated as Equation 4:

Tsub=Tdim+Tblank

(4)

• Tdim is the scan switch on-time for one switching cycle, which equals to one PWM cycle 42 μs (PWM

frequency set as 24 kHz) or 84 μs (PWM frequency set as 12 kHz).

• Tblank is blank time is applied between two adjacent dimming periods, which is from 1 μs to 2 μs selected by

'Blank_Time' bits in Dev_Config11 Register.

One complete frame time Tframe is calculated as Equation 5:

Tframe=Tsub×Scan #

(5)

• Scan # is the total scan switches count.

The LP5813 can be configured to direct-drive mode, TCM-drive mode and mix-drive mode by the 'led_mode'

bits in 'Dev_Config_1' register. The mix-drive mode contains both direct drive mode and TCM-drive mode for

different outputs. With this method, the LP5813 can provide the maximum flexibility for LED configurations of

LED average current, LED count, and PCB layouts.

9.3.2.1 Direct drive mode

The direct drive mode can drive up to 4 LEDs (or 1 RGBW / RGBA / RGBY LED) by the internal constant current

sinks directly, when the 'led_mode' bit is 0h. The typical application circuit is illustrated in Figure 9-4. Each

current sink can support up to 51 mA maximum current. In the register map, LED_x (x = 0, 1, 2, 3) are used as

the name of each outputs for the related settings.

LP5813

SNVSC74 – SEPTEMBER 2023

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