R1211 driving white LED circuit diagram

The R1211 series is a switching boost converter with low power consumption and current control function produced using CM0S technology. Its peripheral circuit is simple, requiring only an inductor, a diode, a field effect transistor and several resistors and capacitors. Its input voltage range is 2.5 ~ 5.5V, suitable for single-cell lithium-ion battery or ordinary dry battery pack power supply. The internal PWM modulation method of the chip can generate an output voltage of up to 15V and can drive three white LEDs in series .

The R1211 series chips adopt a phase compensation feedback loop, which makes the entire boost conversion process more responsive and the output voltage more stable. The maximum duty cycle of the R1211 is 90%. The delay time of the chip's built-in soft start is approximately 10ms. After the circuit is turned on, when the delay time has passed, the protection circuit will determine the current status. If the current duty cycle is the maximum value and remains for a specific time, the output driver port of the chip will be locked by the protection circuit. Thereby shutting off the circuit plays a protective role. An external capacitor can be used to adjust the required delay protection time to adapt to different applications.

The R1212 has a fixed switching frequency of 1.4MHz, allowing the use of small external components and minimizing input and output ripple. It is particularly suitable for applications requiring low input and output noise.

The R1212 driving white LED application circuit is shown in the figure. The control circuit inside the chip will control the external field effect transistor according to the voltage of the FB pin, so the circuit will be stabilized at the set output value. Because all white LEDs in series have very consistent currents, the hue differences between individual white LEDs can be minimized. The white LED current is set by resistor R1 on the feedback pin according to R1=RFB/ILED (UFB=1.0V).

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R1211 is a white LED driver optimized for electronic devices that drive 2 to 4 white LEDs using a single lithium-ion battery. It is an ideal driver that requires small circuit size, high efficiency, and matching white LED brightness.