DM164 datasheet(18/30 Pages) SITI

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點晶科技股份有限公司

SILICON TOUCH TECHNOLOGY INC.

DM164

8x3-CHANNEL CONSTANT CURRENT LED DRIVERS

Version:A.002

Page 17

1st GD Mode

Data Input Cycle

MSEL

LTH

D&G Mode Data

Input Cycle

GCK

2nd GD Mode

Data Input Cycle

FFh

16-bit

COUNTER

IOUT0

(ONEST=L)

FFFFh

FFh

DCK

65536 GCK cycle

1 GCK cycle

384

IOUT0

(ONEST=H)

. . .

< 65536 GCK cycle

Figure 10. Grayscale PWM Operation

Maximum Output Current

The maximum output current is set by an external resistor. The resistor is connected

between Rext and GND. Varying the resistor value can adjust the current scale ranging

from 5mA to 90mA. The reference voltage of REXT terminal (Vrext) is approximately

1.23V. The maximum output current (Imax) value can be calculated roughly by the following

equation:

rext

max

rext

V(V)

R(Ω)

≅

where:

Vrext = 1.23V

Rrext = external resistor.

Global Brightness Control

The global brightness control function can adjust the global current of each color

independently. The output current (Iglobal) can be adjusted in 256 steps from

((1/256)*100)% to 100% of the maximum output current. The following equation can

calculate the global brightness control current (Iglobal)

global

max

GB+1

256

≅×

where:

Imax = the maximum output current.

GB = the global brightness control value for different colors.

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