STEP-UP DC/DC CONVERTER FOR WHITE LED BACK LIGHT
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The R1203x Series are PWM control type step-up DC/DC converter ICs with low supply current.
The R1203x is fully dedicated to drive White LEDs with constant current. Each of these ICs consists of an NMOS FET, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier, a current limit circuit, an under voltage lockout circuit (UVLO), and an over-voltage protection circuit (OVP).
The R1203x can drive white LEDs in constant current with high efficiency by using an inductor, a diode , a resistor and capacitors as external components.
The LEDs current can be set by an external resistance value and can adjust the dimming of LEDs by CE pin according to the signal of PWM. Feedback voltage is 0.2V, therefore power loss by current setting resistance is small and efficiency is good. Maximum duty cycle is internally fixed, Typ. 91%. LEDs can be driven from low voltage. Protection circuits are the current limit of Lx peak current, the over voltage limit of output, and the under voltage lockout function.
It is controllable the dimming of LEDs quickly when the PWM signal (between 200Hz to 300kHz) input to CE pin. If the CE pin input is "L" in the fixed time (Typ. 0.5ms), the IC becomes the standby mode and turns OFF LEDs.
|Supply Current||Typ. 500µA|
|Standby Current||Max. 5µA|
|Input Voltage Range||1.8V to 5.5V|
|Feedback Voltage Accuracy||±1.0% (±10mV)|
|Temperature-Drift Coefficient of Feedback Voltage||±150ppm/°C|
|Oscillator Frequency||Typ. 1.2MHz|
|Maximum Duty Cycle||Typ. 91%|
|Switch ON Resistance||Typ. 1.35Ω|
|UVLO Detector Threshold||Typ. 1.6V|
|Lx Current Limit Protection||Typ. 700mA|
|OVP Detector Threshold||Typ. 29.5V|
|LED dimming control||by external PWM signal (Frequency 200Hz to 300kHz)|
|Ceramic capacitors are recommended||0.22µF|
- ・White LED Backlight for portable equipment
|Data Sheet||Flyer||Design Guide|
|Package Info.||Mark Info.||Quality Assurance Data|
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