R1218X Ricoh Corporation, R1218X Datasheet - Page 6

• Manufacturer Part Number: R1218X
• Description: Step Up DC/DC Converter
• Manufacturer: Ricoh Corporation

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DataSheet
6
R1218X041A
R1218X
VFB Voltage, Oscillator Frequency, Maximum Duty
Test Circuit
TYPICAL APPLICATIONS
LED current can be set with feedback resister(R1)
(1) LED dimming control by PWM signal to CE pin
LED dimming control is possible by forcing PWM signal to CE pin. When the power-on or start up with CE pin,
softstart function works, however, after that, if the CE pin is set as "L" and set CE pin "H" again during the shutdown
delay time, softstart function is disabled and starts up fast to normal mode, therefore 200Hz to 5kHz PWM signal is
standard. By the CE pin input, LED turns on and off. Average LED current varies depending on the duty cycle of CE input.
Too high frequency PWM signal is not effective because of its delay.
(2)Dimming control by DC voltage
LED dimming control is also possible by using the DC voltage to V
resisters, R1 and R2 in the figure 4.
I
(3)Dimming control by feedback voltage and filtered PWM signal
LED dimming control is also possible by using the feedback voltage and filtered PWM signal. LED current is adjustable
according to the "H" level (VH) and "L" level(VL) of PWM signal and resisters, R1, R2, R3, and R4 in the figure5.Duty
LED
C1
1uF
I
4
LED
LED Current setting
LED Dimming Control, Softstart
U
=(DC-0.2)/R2-0.2/R1
=V
.com
FB
CE
GND
GND
GND
GND
V V V V
/R1
CE
CE
GND
GND
CE
CE
GND
GND
IN
IN
IN
IN
V V V V
IN
IN
IN
IN
L1
22 uH
V V V V
V V V V
V V V V
L L L L
L L L L
OUT
OUT
OUT
OUT
X X X X
FB
FB
FB
FB
X X X X
FB
FB
FB
FB
R1
10
C2
0.22uF
OVP Detector Threshold, OVP Released Voltage
Test Circuit
R1218X062A
C1
1uF
FB
GND
GND
GND
GND
pin. LED current is adjustable by DC voltage and
V V V V
CE
CE
CE
CE
IN
IN
IN
IN
CE
CE
CE
CE
GND
GND
GND
GND
V V V V
IN
IN
IN
IN
L1
22uH
V V V V
V V V V
V V V V
L L L L
OUT
OUT
OUT
OUT
V V V V
L L L L
OUT
OUT
OUT
OUT
X X X X
X X X X
FB
FB
FB
FB
FB
FB
FB
FB
R1
10
C2
0.22uF