On/OffData

15

MSB

On/Off

OUT15

On/Off

OUT14

On/Off

OUT13

0

LSB

On/Off

OUT2

On/Off

OUT1

On/Off

OUT0

TLC5923

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SLVS550B – DECEMBER 2004 – REVISED JANUARY 2013

Output Enable

All OUTn channels of TLC5923 can switched off with one signal. When BLANK signal is set to high, all OUTn are

disabled, regardless of On/Off status of each OUTn. When BLANK is set to low, all OUTn work under normal

conditions.

Table 1. BLANK Signal Truth Table

BLANK

OUT0 - OUT15

LOW

Normal condition

HIGH

Disabled

Setting Channel On/Off Status

All OUTn channels of TLC5923 can be switched on or off independently. Each of the channels can be

programmed with a 1-bit word. On/Off data are entered for all channels at the same time. The complete On/Off

data format consists of 16 x 1-bit words, which form a 16-bit wide data packet. The channel data is put one after

another. All data is clocked in with MSB first. Figure 8 shows the On/Off data format.

Figure 8. On/Off Data Format

To input On/Off data into On/Off register MODE must be set to low. The internal input shift register is then set to

16 bit width. After all serial data is clocked in, a rising edge of XLAT is used to latch data into the On/Off register.

The ON/OFF register is an edge-triggered latch of XLAT signal. BLANK signal does not need to be high to latch

in new data. Figure 14 shows the On/Off data input timing chart.

Delay Between Outputs

The TLC5923 has graduated delay circuits between outputs. These delay circuits can be found in the constant

current block of the device (see Functional Block Diagram). The fixed delay time is 20 ns (typical), OUT0 has no

delay, OUT1 has 20 ns delay, OUT2 has 40 ns delay, etc. This delay prevents large inrush currents, which

reduce power supply bypass capacitor requirements when the outputs turn on. The delay works during switch on

and switch off of each output channel. LEDs that have not turned on before BLANK is pulled high will still turn on

and off at the determined delayed time regardless of the state of BLANK. Therefore, every LED will be

illuminated for the amount of time BLANK is low.

Serial Interface Data Transfer Rate

The TLC5923 includes a flexible serial interface, which can be connected to microcontroller or digital signal

processor. Only 3 pins are in required to input data into the device. The rising edge of SCLK signal shifts the

data from SIN pin to internal shift register. After all data is clocked in, a rising edge of XLAT latches the serial

data to the internal registers. All data is clocked in with MSB first. Multiple TLC5923 devices can be cascaded by

connecting SOUT pin of one device with SIN pin of following device. The SOUT pin can also be connected to

controller to receive LOD information from TLC5923.

Copyright © 2004–2013, Texas Instruments Incorporated

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