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 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. 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 6 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 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.
Packages are standard SOT-23-6 and very tiny DFN(PLP)1820-6. |
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 Input voltage |
1.8V to 5.5V |
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Built-in 400mA, 1.5Ω, 20V Nch MOSFET (R1218xxx1A) |
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Built-in 400mA, 1.5Ω, 29V Nch MOSFET (R1218xxx2A) |
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| Oscillator
Frequency(PWM control) |
1.2MHz |
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| Maximum Duty Cycle |
Typ. 91% |
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| Feedback
Voltage |
Typ. 0.2V |
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| UVLO Threshold Voltage |
Typ. 1.6V (Hysteresis Typ. 0.1V) |
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| Lx Current limit Protection |
Typ. 700mA |
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Over Voltage Protection (OVP) Threshold |
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Typ. 9.5V (R1218x02XA)
Typ. 14.0V (R1218x031A)
Typ. 18.5V (R1218x041A)
Typ. 23.0V (R1218x052A)
Typ. 27.5V (R1218x062A) |
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LED dimming control |
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by external PWM signal (Frequency 200Hz to 5kHz) to CE pin |
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by feedback voltage and filtered PWM signal (high frequency) |
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| Packages |
SOT-23-6 or DFN(PLP)1820-6 |
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White LED Backlight for portable equipment
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| * All PDF files are less than 1MB unless otherwise stated. |
| * If you don't have Adobe Reader, you can download free. |
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Technical Info.
Technical Information on Ricoh Power Management ICs.
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Product Catalog
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| Selection guide is available for download in PDF format. |
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Non-promotion / Discontinued Products
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R1218x
Series
