Avoid Radio-band Noise Interference In Car Electronics With Torex XC9252 Series High Withstand Voltage DC/DC Converters
A switching regulator periodically switches the current ON/OFF to convert the output to a desired output voltage.
A variety of techniques are needed for selecting components for car electronics.
Here we introduce the selection know-how cultivated at “Torex”, a professional group that specializes in power ICs.
To avoid switching regulator frequency interference
A switching regulator periodically switches the current ON/OFF to convert the output to a desired output voltage. This provides higher efficiency than a linear regulator which loses some power as heat when converting the output voltage, but also has the disadvantage of switching-generated noise. In particular, interference with AM radio frequencies is a problem.
To avoid this frequency interference, switching regulators that allow changing of the switching frequency have been developed. These regulators let you set a switching frequency that avoids frequency bands where there is a concern of interference, such as AM radio.
Torex's "XC9252 series" and "XC9270/XC9271 series" of high withstand voltage DC/DC converters are synchronized to an external clock, and this enables the switching frequency to be varied within a range of ±25%. On the "XC9252 series", an external resistance can be used to set any frequency.
The XC9252 series is a 30V operation step-down DC/DC controller IC. The external P-ch driver transistor is used to achieve a stable operation under low input voltage. Low ESR capacitors such as ceramic capacitors can be used for the load capacitor (CL).
A 0.8V reference voltage source is incorporated, and the output voltage can be set freely from 1.0V using external resistors (RFB1, RFB2).
300kHz to 600kHz can be selected for the switching frequency by connecting an external resistor to the ROSC pin. The generation of unneeded noise can be reduced by this synchronization with an external CLK within ±25% of the internal clock using the MODE/SYNC pin. In automatic PWM/PFM control, the IC operates by PFM control when the load is light to achieve high efficiency over the full load range from light to heavy.
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