LP5520 datasheet(12/45 Pages) TI2

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TEMPERATURE, °C

1500

1450

1400

1350

1300

1500

1450

1400

1350

1300

LP5520

SNVS440B – MAY 2007 – REVISED MARCH 2016

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Feature Description (continued)

Figure 15. Compensated Blue LED Intensity vs Temperature

7.3.2.2 LED Brightness Control

The LED brightness is defined by two factors, the current through the LED and the PWM duty cycle. The

constant current outputs ROUT, GOUT, and BOUT can be independently set to sink between 0 and 60 mA. The

8-bit current control has 255 levels, and the step size is 235 µA. In manual mode the current is defined with the

current control (R/G/B) registers (01H, 02H, and 03H). In automatic mode the current settings are loaded from

the EEPROM.

The PWM control has 12-bit resolution, which means 4095 steps. The minimum pulse width is 200 ns, and the

frequency can be set to either 1.2 kHz or 19.2 kHz. The duty cycle range is from 0 to 100% (0 to 4095). The

output PWM value is obtained by multiplication of three factors. The first factor is the temperature-based value

from the EEPROM. The second factor is the correction register setting, which is independent for each color. The

third factor is the brightness register setting, which is common to all colors.

The temperature-based PWM values are stored in the EEPROM at 16°C intervals starting from –40°C and

ending to 120°C. PWM values for the temperatures between the stored points are interpolated.

LED brightness has 3-bit logarithmic control. The control bits are in the pwm_brightness (04H) register. The 3-bit

value defines a multiplier for the 12-bit PWM value obtained from the memory according to Table 1.

LP5520 Arkusz danych(PDF) 12 Page - Texas Instruments