RICOH R1218x Series PWM Step-up DC DC Converter for White LED Quick Reference Guide

R1218x Series

PWM Step-up DC/DC Converter for White LED

The R1218x Series are CMOS-based PWM step-up DC/DC converters, which are optimized to drive white LEDs with constant current. R1218x includes an under-voltage lockout circuit (UVLO), over-voltage protection circuit (OVP). By simply using an inductor, (a diode), a resistor, and a capacitor as external components, white LEDs can be driven with constant current efficiently. R1218xxx1A for 2 to 4 lights contains an internal diode while R1218xxx2A for 5 to 7 lights requires an external diode. The LED current can be determined by the value of current setting resistor. The brightness of the LEDs can be adjusted by applying a PWM signal to the CE or VFB pin.

FEATURES • Supply Current (IDD) ························Typ. 500μA (VIN=5.5V, VFB=0V, Lx at no load) • Oscillator Frequency (fosc)·······················1.2MHz • Standby Current (Istandby) ·················Max. 3μA (VIN=5.5V, CE="L") • Oscillator Maximum Duty Cycle (Maxduty) ···Typ. 91% to 92% • Input Voltage Range (VIN) ···············1.8V to 5.5V (Absolute maximum rating : 6.5V) • UVLO Detect Voltage (VUVLO)··················Typ. 1.6V • Feedback Voltage (VFB) ··················0.2V • Coil-current Limit Circuit ···························Current limit Typ. 700m A • Feedback Voltage Accuracy ···········± 10m V • Over Voltage Protection Circuit (OVP) • Temp. coeff. of Feedback Voltage·····± 150ppm/°C • Packages················································DFN(PLP)1820-6, SOT-23-6

BLOCK DIAGRAM TYPICAL APPLICATIONS

R1218x R1218x041A R1218x072A VFB VIN LX VOUT L1

Error Amp UVLO 1μF

PWM Comp. C2 0.22μF

Switch C1

R Q OVP VIN LX 1μF

Control C2

Vref 0.22μF

OSC VIN LX

ff ic ie CE VOUT

Slope Current Current Compensation Protect sense CE VOUT

GND VFB

Shutdown Chip Enable delay

GND VFB

CE GND

For , only R1218xxx1A.

SELECTION GUIDES

.xx. : Specify the OVP Voltage.

Halogen Free Package Q'ty per Reel Part No.

(.02.) OVP : 9.5V, (.03.) OVP : 14.0V, (.04.) OVP : 18.5V,

DFN(PLP)1820-6 5,000 pcs R1218K.xx$$ -TR

(.05.) OVP : 23.0V, (.06.) OVP : 27.5V, (.07.) OVP : 31.5V

SOT-23-6 3,000 pcs R1218N.xx$$ -TR-FE

.$$. : Specifies built-in diode. (.1A.) With diode, (.2A.) Without diode, .xx$$. Combination : 021A, 031A, 041A, 052A, 062A, 072A (Other combinations are not available.)

PACKAGES (Top View) TYPICAL CHARACTERISTIC

DFN(PLP)1820-6 SOT-23-6 R1218x041A Efficiency vs. LED Current

Topt=25°C, VIN=4.2V

1 CE 1 CE 2 VFB 2 VOUT 3 Lx 3 VIN 4 GND 4 Lx 5 VIN 5 GND 6 VOUT 6 VFB

LED Current l LED (m A)

∗) The tab is substrate level (GND).

APPLICATIONS • White LED driver for hand-held equipment

No.EK-166-111001 Step-up DC/DC Converter