RICOH R1218x SERIES Step-up DC DC Converter for White LED Backlight User Guide and Specifications
Summary
The R1218x series is a high-efficiency, PWM control step-up DC/DC converter IC specifically designed for constant current white LED backlighting. This manual provides comprehensive details on the device's operation, including its built-in protection circuits (OVP, UVLO), low voltage inputs, and dimming control options. It is ideal for engineers developing portable equipment or lighting systems that require reliable, efficient, and regulated high-output white LED illumination.
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R1218x SERIES
Step-up DC/DC converter for White LED Backlight
NO.EA-166-111123
OUTLINE The R1218x Series are PWM control type step-up DC/DC converter ICs with low supply current. The R1218x is fully dedicated to drive White LED 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), an over-voltage protection circuit (OVP). The R1218x can drive white LEDs with high efficiency with low supply current. A diode is built-in the R1218xxx1A, therefore it is possible to drive up to 4LEDs without an external diode. The R1218xxx2A, an external diode is necessary, however, up to 7 serial LEDs can be driven with the R1218xxx2A. Constant current can be set with an external resistance value. Dimming control is possible by PWM signal for CE pin. Feedback voltage is 0.2V, therefore power loss by current setting resistor is small and efficiency is good. Maximum duty cycle is internally fixed, Typ. 91% to 92%. 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. Packages are standard SOT-23-6 and very tiny DFN(PLP)1820-6.
FEATURES • Input voltage.................................................. 1.8V to 5.5V • Built-in 400m A, 1.5Ω, 20V Nch MOSFET and diode (R1218xxx1A) • Built-in 400m A, 1.5Ω, 33V Nch MOSFET (R1218xxx2A) • Oscillator Frequency (PWM control)............. 1.2MHz • Maximum Duty Cycle Typ. 91% to 92% • Feedback Voltage Typ. 0.2V • UVLO Threshold Voltage Typ. 1.6V (Hysteresis Typ. 0.1V) • Lx Current limit Protection............................. Typ. 700m A • Over Voltage Protection (OVP) Threshold.... Typ. 9.5V (R1218x021A)
Typ. 14.0V (R1218x031A) Typ. 18.5V (R1218x041A) Typ. 23.0V (R1218x052A) Typ. 27.5V (R1218x062A) Typ. 31.5V (R1218x072A)
• LED dimming control..................................... by external PWM signal (Frequency 200Hz to 5k Hz) to CE pin
by feedback voltage and filtered PWM signal (high frequency)
• Packages DFN(PLP)1820-6, SOT-23-6
APPLICATION • White LED Backlight for portable equipment
Page Summary Contents For RICOH R1218x SERIES Step-up DC DC Converter for White LED Backlight User Guide and Specifications
Manual Details
| Brand | Ricoh |
|---|---|
| Pages | 19 |
| File Size | 306.76 KB |
| Published | June 02, 2026 |
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Frequently Asked Questions
What is the required input voltage for the R1218x converter?
The recommended input voltage (VIN) ranges from 1.8V to 5.5V.
How can I control the brightness of the LED backlight?
Dimming is achieved using an external PWM signal applied directly to the CE pin.
Which version supports driving more than four LEDs, and how many?
The R1218xxx2A requires an external diode but can drive up to 7 serial LEDs.
Is power loss minimal when setting constant current?
Yes, because the feedback voltage is only 0.2V, resulting in small power loss.