XC6237 Series ■OPERATIONAL EXPLANATION <Output Voltage Control> The voltage divided by resistors R1 & R2 is compared with the internal voltage reference by the error amplifier. The P- channel MOSFET, which is connected to the VOUT pin, is then driven by the subsequent output signal. The output voltage at the V OUT pin is controlled and stabilized by a system of negative feedback. The GO function monitors the output current and switches IC’s consumption current according to the level of output current. V IN - Error Amp + Voltage Green Current Reference V Operation Limit O UT R1 R2 RDCHG ON/OFF each CE Control circuit CE VSS ※Diodes inside the circuits are ESD protection diodes and parasitic diodes. <Green Operation Function > The GO enables the IC to switch automatically the supply current to the high speed (HS) mode or the power save (PS) mode according to the level of output current. While having both high-speed operation and low supply current state, the series can acquire high efficiency. The switching point of the HS mode and the PS mode is being fixed inside the IC. When the output current becomes IGOR 0.5mA (MIN.) or below, the mode changes automatically to the PS mode and it can reduce supply current in light load. Also when the output current becomes IGO 10mA (MAX.) or more, the mode changes automatically to the HS mode and the IC becomes high speed operation. When the input voltage is lower than the nominal output voltage or the input / output voltage difference is small, it may operate in the HS mode regardless of the output current. <CE Function> The IC's internal circuitry can be shutdown via the signal from the CE pin with the XC6237 series A/B type. In shutdown mode, output at the VOUT pin will be pulled down to the VSS level via R1 & R2. However the XC6237 series A type has the CL auto- discharge function is able to discharge the electric charge at the CL via the internal auto-discharge resistance, when IC is shutdown mode and power is supplied to the VIN pin, as a result the VOUT pin quickly returns to the VSS level. The output voltage becomes unstable, when the CE pin is open. Please input a certain voltage within an electrical characteristic into CE pin. If this IC is used with the correct output voltage for the CE pin, the logic is fixed and the IC will operate normally. However, supply current may increase as a result of through current in the IC's internal circuitry when medium voltage is input. < Current Limit, Short-Circuit Protection> The XC6237 series limit output current by current fold-back circuit. When the output current reaches the current limit level (TYP. 250mA), the current fold-back circuit operates and the output current also drops as the output voltage drops. The output voltage drops further and output current decreases. When the output pin is shorted, the output current is I SHORT (TYP> 25mA) and can be used safely by short-circuit. 10/27 Document Outline XC6237 (2) XC6237_ETR03100-001 XC6237 XC6237_ETR03100-001