
R1201x SERIES
STEP-UP DC/DC CONVERTER FOR WHITE LED BACK LIGHT
NO.EA-207-100823
1
OUTLINE
The R1201x Series are PWM control type step-up DC/DC converter ICs with low supply current.
The R1201x is fully dedicated to drive White LEDs with constant current. Each of these ICs consists of an
NMOS FET, a forward diode, 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 R1201x can drive white LEDs in constant current with high efficiency by using an inductor, a resistor and
capacitors as external components. A diode is built-in; therefore it is possible to drive up to 5 serial white LEDs
without an external diode.
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. The oscillator frequency can be selected from 1MHz or 1.2MHz.
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.
FEATURES
Supply Current ...........................................................Typ. 450μA (R1201xxx3A/4A)
Typ. 500
μA (R1201xxx1A/2A)
Standby Current .........................................................Max. 5μA
Input Voltage Range ..................................................1.8V to 5.5V
Feedback Voltage ......................................................0.2V
Feedback Voltage Accuracy.......................................±10mV
Temperature-Drift Coefficient of Feedback Voltage ...±150ppm/°C
Oscillator Frequency ..................................................Typ. 1MHz, 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............................................Select from 9.5V, 14.0V, 18.5V, 20.6V, 21.6V
Switching Control .......................................................PWM
LED dimming control..................................................by external PWM signal (Frequency 200Hz to 300kHz)
Packages ...................................................................DFN1616-6, SOT-23-6
Ceramic capacitors are recommended......................0.22μF (R1201x02xA/ 03xA/ 04xA)
1
μF (R1201x05xA)
APPLICATION
White LED Backlight for portable equipment