t

(ns)=t

(ns)

GSn

´

OUTON

GSCLK

(3)

GS15.11

MSB

191

GSOUT15

GS

5.

1

0

GS1.0

GS0.11

GS0.0

180

12

11

LSB

0

GS14.11

179

GSOU 14toGS

T

OUT1

GSOUT0

TLC59461

When the IC powers on, the data in the shift register and latch are not set to any default value. Therefore, GS

data must be written to the GS latch before turning the constant-current output on. Additionally, BLANK should

be high when the device is powered on, to prevent the outputs from turning on before the proper grayscale and

dot correction values are written. All constant-current outputs are always off when BLANK is high.

Where:

• t

• GSn = the programmed grayscale value of output n (GSn = 0 to 4095d)

If XLAT goes high during a grayscale cycle, then new GS data are immediately latched into the GS latch. This

action can cause the outputs to turn on or off unexpectedly. For proper operation, GS data should only be

latched into the IC at the end of a GS period when BLANK is high.

When MODE is low, the input shift register works as a GS shift register. The shift registers and data latches are

each 192 bits in length, and are used to set the PWM timing for each constant-current driver. Figure 25 shows

the GS serial data configuration. Refer to Figure 12 for a timing diagram for writing data into the shift register and

latch. The driver on-time is set by the data in the GS data latch. GS data present on the SIN pin are clocked into

the shift register with each rising edge of the SCLK pin. Data are shifted in MSB first. Data are latched from the

shift register into the GS data latch with a rising edge on the XLAT pin.

If there are any unconnected output LED lamps (including connection failures or short-circuits), the grayscale

data corresponding to the unconnected output should be set to '0' before turning on the LEDs. Otherwise, the

Figure 25. Grayscale Serial Data Configuration

16

Submit Documentation Feedback

Copyright © 2008–2009, Texas Instruments Incorporated

Product Folder Link(s): TLC59461