LP3936 Datasheet, PDF (15/20 Pages) National Semiconductor (TI) – Lighting Management System for Six White LEDs and One RGB or FLASH LED

Boost Converter Typical Performance Characteristics V_IN = 3.6V, V_OUT = 4.55V if not
otherwise stated. (Continued)
Boost Line Regulation
Boost Load Regulation, 50 mA–100 mA
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RGB LED Driver
The RGB driver has three outputs that can independently
drive one RGB LED or three LEDs of any kind. User has
control over the following parameters separately for each
LED:
• ON and OFF (start and stop time in blinking cycle)
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• DUTY
(PWM brightness control)
• SLOPE
(dimming slope)
• ENABLE (direct enable control)
The main blinking cycle is controlled with 2-bit CYCLE con-
trol (0.25 / 0.5 / 1.0 / 2.0s).
RGB PWM Operating Principle
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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. RGB_EN input can be used for external hardware
PWM control. RGB_EN input can be used as direct on/off or
brightness (PWM) control. If RGB_EN input is not used, it
must be tied to V_{DD_IO}. Recommended maximum frequency
of RGB LED external PWM control is 1 MHz.
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 6.67 kHz in normal mode.
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Normal Mode PWM Waveforms at different duty
settings
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