LP3936 datasheet(15/20 Pages) NSC

15 / 20 page

Boost Converter Typical Performance Characteristics V

IN = 3.6V, VOUT = 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)

• 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).

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RGB PWM Operating Principle

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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