R1218K021A RICOH [RICOH electronics devices division], R1218K021A Datasheet - Page 8

• Manufacturer Part Number: R1218K021A
• Description: Step-up DC/DC converter for White LED Backlight
• Manufacturer: RICOH [RICOH electronics devices division]

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TEST CIRCUITS
R1218x
Selection of Inductors
The peak current of the inductor at normal mode can be calculated as next formula:
When the start-up or dimming control by CE pin, transient current flows, the peak current must be equal or
less than the current limit of the IC. The peak current should not beyond the rating current of the inductor. For
example, for 4 serial LED drive from V
Selection of Capacitors
Set 1µF or more value bypass capacitor C1 between V
Set 0.22µF or more capacitor C2 between V
I
LX
peak=1.25 × I
VFB Voltage, Oscillator Frequency,
Supply Current Test Circuit
V
CE
GND
Maximum Duty Test Circuit
IN
A
R1218x
Series
LED
× V
V
CE
GND
IN
V
V
OUT
OUT
R1218x
L
FB
Series
X
/ V
IN
OSCILLOSCOPE
+ 0.5 × V
V
V
OUT
L
FB
X
IN
=3.6V, recommendation value of the inductor is 22µH or more.
IN
× (V
OUT
OUT
and GND pin.
− V
IN
IN
) / (L × V
pin and GND pin as close as posible.
OUT
OVP Released Voltage Test Circuit
× fosc)
V
CE
GND
UVLO Detector Threshold,
OVP Detector Threshold,
IN
UVLO Released Voltage
V
CE
GND
IN
R1218x
Series
R1218x
Series
V
V
OUT
V
L
FB
V
X
OUT
L
FB
X
OSCILLOSCOPE
OSCILLOSCOPE