R1218K021A RICOH [RICOH electronics devices division], R1218K021A Datasheet

Manufacturer Part Number

R1218K021A

Description

Step-up DC/DC converter for White LED Backlight

Manufacturer

RICOH [RICOH electronics devices division]

Datasheet

1.R1218K021A.pdf (21 pages)

OUTLINE

NMOS FET, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier, an under voltage

lockout circuit (UVLO), an over-voltage protection circuit (OVP), and so on.

R1218xxx1A, therefore it is possible to drive up to 4LEDs without an external diode. The R1218xxx2A, an

external diode is necessary, however, up to 6 serial LEDs can be driven with the R1218xxx2A.

CE pin. 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.

FEATURES

APPLICATION

Step-up DC/DC converter for White LED Backlight

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

The R1218x can drive white LEDs with high efficiency with low supply current. A diode is built-in the

Constant current can be set with an external resistance value. Dimming control is possible by PWM signal for

Packages are standard SOT-23-6 and very tiny PLP1820-6.

• Operating voltage.......................................... 1.8V to 5.5V

• Built-in 400mA, 1.5Ω, 20V Nch MOSFET (R1218xxx1A)

• Built-in 400mA, 1.5Ω, 29V Nch MOSFET (R1218xxx2A)

• Oscillator Frequency (PWM control)............. 1.2MHz

• Maximum Duty Cycle .................................... Typ. 91%

• Feedback Voltage ......................................... Typ. 0.2V

• UVLO Threshold Voltage .............................. Typ. 1.6V (Hysteresis Typ. 0.1V)

• Lx Current limit Protection............................. Typ. 700mA

• Over Voltage Protection (OVP) Threshold .... Typ. 9.5V (R1218x021A)

• LED dimming control..................................... by external PWM signal (Frequency 200Hz to 5kHz) to CE pin

• Packages ...................................................... SOT-23-6 or PLP1820-6

• White LED Backlight for portable equipment

Typ. 14.0V (R1218x031A)

Typ. 18.5V (R1218x041A)

Typ. 23.0V (R1218x052A)

Typ. 27.5V (R1218x062A)

by feedback voltage and filtered PWM signal (high frequency)

R1218x SERIES

NO.EA-166-070905