LP3933SL NSC [National Semiconductor], LP3933SL Datasheet - Page 12

• Manufacturer Part Number: LP3933SL
• Description: Lighting Management System for Six White LEDs and Two RGB or FLASH LEDs
• Manufacturer: NSC [National Semiconductor]

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Dual RGB LED Driver
The RGB driver has six outputs that can independently drive
2 separate RGB LEDs or six LEDs of any kind. User has
control over the following parameters separately for each
LED:
The main blinking cycle is controlled with 2-bit CYCLE con-
trol (0.25 / 0.5 / 1.0 / 2.0s).
RGB_START is the master enable control for the whole RGB
function. The internal PWM and blinking control can be
disabled by setting the RGB_PWM control LOW. In this case
the individual enable controls can be used to switch outputs
on and off. PWM_LED input can be used for external hard-
ware PWM control.
In the normal PWM mode the R, G and B switches are
controlled in 3 phases (one phase per driver). During each
phase the peak current set by external resistor is driven
through the LED for the time defined by DUTY setting
(0 µs–50 µs). As a time averaged current this means
0%–33% of the peak current. The PWM period is 150 µs and
the pulse frequency is 6.7 kHz in normal mode.
• ON and OFF (start and stop time in blinking cycle)
• DUTY
• SLOPE
• ENABLE
RGB PWM Operating Principle
(PWM brightness control)
(turn-on and turn-off slope)
(output enable control)
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In the FLASH mode all the outputs are controlled in one
phase and the PWM period is 50 µs. The time averaged
FLASH mode current is three times the normal mode current
at the same DUTY value.
Blinking can be controlled separately for each output. On
and OFF times determine, when a LED turns on and off
within the blinking cycle. When both ON and OFF are 0, the
LED is on and doesn’t blink. If ON equals OFF but is not 0,
the LED is permanently off.
Normal Mode PWM Waveforms at Different Duty
Example Blinking Waveforms
Settings
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