POWER DISSIPATION CALCULATION

P

=(V

I

)+V

I

´

D

CC

CC

OUT

OLCMax

´

´

´

N

DCn

63d

´

d

PWM

(6)

EXTENDED SERIAL INTERFACE

TLC59461

SLVS896A – NOVEMBER 2008 – REVISED MARCH 2009............................................................................................................................................... www.ti.com

The device power dissipation must be below the power dissipation rate of the device package to ensure correct

operation. Equation 6 calculates the power dissipation of the device:

Where:

• P

D = device power dissipation

• V

CC = device supply voltage

• I

CC = device supply current

• V

OUT = OUTn voltage when driving LED current

• I

OLCMax = LED current adjusted by RIREF resistor

• DCn = maximum DC value for OUTn

• N = number of OUTn driving LED at the same time

• d

PWM = duty cycle defined by BLANK pin or GS PWM value

The TLC59461 has an extended serial interface with the following functions:

1. Independently accessible GS shift register of OUT0 to OUT7 or OUT8 to OUT15

2. SOUT half clock delay

When XHALF is low, the extended serial interface becomes active. Either the OUT0 to OUT7 GS shift register or

the OUT8 to OUT15 GS shift register is selected in advance by counting the XLAT pulses while BLANK is high

(one XLAT pulse selects the OUT0 to OUT7 GS shift register and two XLAT pulses select the OUT8 to OUT15

GS shift register), as shown in Figure 32. One or two XLAT pulses while BLANK is high must be input before

sending the serial data.

SOUT outputs serial data at the falling edge of SCLK, delaying half a clock longer than the normal serial

interface mode. SIN reads data at the rising edge of SCLK at the same as the normal serial interface mode. This

configuration ensures a longer distance serial interface. Figure 33 shows the output timing of the extended serial

interface mode.

SOUT outputs the status information data only when the data of OUT8 to OUT15 are shifted in, as shown in

Figure 34 and Figure 35. The status information data configuration when XHALF is low is shown in Figure 36.

Figure 37 shows the recommended ac timing widths of the extended serial interface. Note that tWL2, tSU7, and tH3

are only effective when XHALF is low.

Figure 38 and Figure 39 show power-on sequence examples of this mode. BLANK should be high when the

device is powered on to prevent the outputs from turning on before the proper GS and DC values are written.

The extended serial interface mode is available only in the GS PWM mode (MODE = low). When MODE is high

in the extended serial interface mode (XHALF = low), the TLC59461 becomes the DC mode that is the same as

the normal DC mode.

22

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