LP3936 Datasheet, PDF (17/20 Pages) National Semiconductor (TI) – Lighting Management System for Six White LEDs and One RGB or FLASH LED

RGB LED PWM Control (Note 13) (Continued)
CYCLE[1:0]
RSW
GSW
BSW
RGB_START
RGB_PWM
EN_FLASH
EN_RED_PWM
EN_GREEN_PWM
EN_BLUE_PWM
If ON = 0, OFF = 0 and RGB_PWM = 1, then RGB outputs are continuously on (no blinking), DUTY
controls the brightness and SLOPE is ignored.
If ON and OFF are the same, but not 0, RGB outputs are turned off.
CYCLE sets the blinking cycle: [00] for 0.25s, [01] for 0.5s, [10] for 1s and [11] for 2s. CYCLE setting is
common to all R, G and B drivers.
Enable for R switch
Enable for G switch
Enable for B switch
Master Switch:
RGB_START = 0 → RGB OFF
RGB_START = 1 → RGB ON, starts the new cycle from t = 0
RGB_PWM = 0 → RSW, GWS and BSW control directly the RGB outputs (on/off control only)
RGB_PWM = 1 → Normal PWM RGB functionality (duty, slope, on/off times, cycle)
Flash Mode enable control for RGB. In Flash mode (EN_FLASH = 1) RGB outputs are PWM controlled
simultaneously, not in 3-phase system as in the Normal Mode.
EN_X_PWM = 0 → External PWM control from RGB_EN pin is disabled
EN_X_PWM = 1 → External PWM control from RGB_EN pin is enabled
Internal PWM control (DUTY) can be used independently of external PWM control. External PWM has
the same effect on all enabled colors.
Note 13: Application Note AN-1293, “Driving RGB LEDs Using LP3936 Lighting Management System” contains a thorough description of the RGB driver
functionality including programming examples.
WLED Drivers
White LED drivers drive each white LED with a regulated
constant current. The outputs are combined in two groups,
four outputs for the main display backlight and two outputs
for the sub display backlight. The current is controlled be-
tween 0 and 25.5 mA using the 8-bit current mode DA-
converters. WLED outputs can be used to drive any kind of
LED.
Main and sub display outputs have separate enable control
bits, EN_4LED and EN_2LED.
PWM control of WLED outputs for dimming or on/off control
is possible using RGB_EN pin together with
EN_4LED_PWM and EN_2LED_PWM enable control bits
from the user register. Recommended maximum frequency
of WLED external PWM control is 1 kHz.
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