TLC6989 datasheet(10/72 Pages) TI1

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7.3 Feature Description

7.3.1 Internal Oscillator and Clocks

7.3.1.1 System Clock

The TLC6989 has an internal oscillator which provides a 40MHz system clock for the device. The system clock

is used to operate the digital logic.

Internal Oscillator Watchdog

The internal oscillator watchdog timer (tWD,OSC) is automatically enabled upon exit from POR. If the internal

oscillator stops toggling for more than tWD,OSC, the watchdog expires and holds the logic in reset (POR) until the

oscillator begins toggling again. The internal oscillator is used as the system clock.

7.3.1.2 Continuous Clock Serial Interface (CCSI) Clock

The clock for transmitting data by the CCSI controller is derived from the system clock. There are 16 divider

options available (CCSI_DATA_RATE in register CCSICTRL) to achieve the desired clock frequency for the

daisy chain of LED drivers.

The CCSI clock can be modulated by a programmable digital spread spectrum to improve the system level EMI

performance. Field CCSI_SS_CLKO in register CCSICTRL determines if the spread spectrum is enabled. When

CCSI_DATA_RATE * CCSI_SS_CLKO * 2 is smaller than 120kBit/s, a modulation frequency of 30kHz is used.

Otherwise the modulation frequency is 120kHz.

7.3.2 Continuous Clock Serial Interface (CCSI)

The continuous clock series interface (CCSI) provides access to the programmable functions and registers of

the LED drivers that are connected in a daisy chain between the CCSI controller and CCSI peripheral. The

serial data output (SOUT) and serial clock output (CLK_O) are used for the CCSI controller. When the CCSI

controller is not transmitting, the SOUT is set to logic HIGH, while the CLK_O remains active and continuous.

The continuous clock starts after the device powers up. To start transmission by the CCSI controller, the device

needs to be in NORMAL state and the flag FLAG_POR has to be cleared.

The CCSI peripheral consists of one wire, which is the serial data input (SIN). The data is shifted in using the

same clock source as CLK_O.

TLC6989

SLVSHF5 – NOVEMBER 2024

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TLC6989 Datasheet(PDF) 10 Page - Texas Instruments