R1280D002X Datasheet, PDF (26/26 Pages) RICOH electronics devices division – 2CH PWM DC/DC Controller

and capacitor.
s TECHNICAL NOTES on EXTERNAL COMPONENTS
q External components should be set as close to this IC as possible. Especially, wiring of the capacitor connected
to VIN pin should be shortest.
q Enforce the ground wire. Large current caused by switching operation flows through GND pin. If the impedance
of ground wire is high, internal voltage level of this IC might fluctuate and operation could be unstable.
q Recommended capacitance value of C3 is equal or more than 4.7µF. Recommended maximum voltage
tolerance of C3 is three times as large as set output voltage or more, because the external transistor might
generate hi voltage with a shape of spike because of an effect from inductor.
q If the spike noise of VOUT is too large, the noise is feedback from VFB1 pin and operation might be unstable. In
that case, use the resistor ranging from 10kΩ to 50kΩ as R5 and try to reduce the noise level. In the case of
VOUT2, use the resistor as much as 10kΩ as R6.
q Select an inductor with low D.C. current, large permissible current, and uneasy to cause magnetic saturation. If
the inductance value is too small, ILX might be beyond the absolute maximum rating at the maximum load.
q Select a Schottky diode with fast switching speed and large enough permissible current.
q Recommended capacitance value of C1 and C2 is as much as Ceramic 10µF. In case that the operation with the
system of DC/DC converter would be unstable, use tantalum capacitors with higher ESR than ceramic capacitor.
Use a capacitor with three times as large as voltage tolerance of the capacitor.
q In this IC, for the test efficiency, Latch release function is included. By forcing (VIN-0.3) V or more voltage to
DTC1 pin or DTC2 pin, Latch release function works.
q Consider the threshold voltage of Power MOSFET transistor. Select an appropriate MOSFET transistor,
depending on the input voltage in order to make the MOSFET turn on completely.
q Performance of the power controller with using this IC depends on external components. Each component,
layout should not be beyond each absolute maximum rating such as voltage, current, and power dissipation.
Rev.1.10
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