lp5526tlx National Semiconductor Corporation, lp5526tlx Datasheet - Page 15

• Manufacturer Part Number: lp5526tlx
• Description: Lighting Management Unit With High Voltage Boost Converter With Up To 150ma Serial Flash Led Driver
• Manufacturer: National Semiconductor Corporation

Functionality of Color LED
Outputs (RLED, GLED, BLED)
FLASH LED DRIVING USING RGB DRIVERS
RGB drivers can be connected in parallel and used as a
flash LED driver (see Typical application 2). Flash LEDs can
be powered through the boost converter. Flash LEDs are
controlled basically the same way as RGB LEDs controlling
is previously described. Additional safety mode is introduced
for FLASH LED driving to avoid prolonged flash and damage
to application. FLASH can be done in 3 different ways:
1. Using external PWM control
2. Controlling RGB max current register values
3. Using Flash mode
1. Using External PWM control
In this case pre-flash brightness is adjusted by adjusting the
pulse width of PWM signal
2. Controlling RGB Max Current Register Values
In this case pre-flash brightness is adjusted by adjusting the
current values in the RGB max current register. Note that in
this mode flash control speed and timing depends on the I
communication speed.
• Enable RGB functions and disable PWM mode (EN-
• Enable RGB constant current mode (CC_SW = 0)
• Write pre-flash values for each output to RGB max cur-
(Continued)
_RGB = 1, RGB_PWM = 0)
rent register (e.g. 00b for 25% of maximum current)
Using External PWM Control for Flash
2
C
15
• Enable external PWM pin by writing EN_PWM_PIN bit
• Use EN_EXT_R_PWM, EN_EXT_G_PWM and EN-
• Enable RGB constant current mode, if external ballast
• Disable internal RGB PWM mode (RGB_PWM = 0)
• Write wanted maximum current values for each output to
• Enable RGB functions (EN_RGB = 1, RSW= 1, GSW= 1,
• Use external PWM control pin (GPIO[0]/PWM) to intro-
• Start pre-flash by switching on the LEDs (RSW = 1, GSW
• Start flash by writing each output maximum current val-
• Stop flash by switching off the LEDs (RSW = 0, GSW = 0,
high
_EXT_B_PWM bits to select, which LED outputs are
controlled by the external PWM control. Output which
external PWM control is not selected will be on constantly
regardless of the state of the external PWM pin.
resistors are not used (CC_SW = 0)
RGB max current register (e.g. 11b for maximum current)
BSW = 1)
duce pre-flash and flash.
= 1, BSW = 1). Pre-flash brightness can be adjusted also
by setting on only one or two LEDs during the pre-flash
ues to RGB max current register
BSW = 0)
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