600毫安输出电流宽输入电压从4.5V到40V开机复位检测CXSD62225低ESR电容稳定低电磁干扰转换器软启动

1.产品概述                       2.产品特点
3.应用范围                       4.下载产品资料PDF文档 
5.产品封装图                     6.电路原理图                   
7.功能概述                        8.相关产品

七,功能概述

Main Control Loop
The CXSD62225 is a constant frequency, synchronous rectifier and current-mode switching regulator. In normal
operation,the internal upper power MOSFET is turned on each cycle.The peak inductor current at which ICMP
turn off the upper MOSFET is controlled by the voltage on the COMP node,which is the output of the error amplifier(EAMP). An external resistive divider connected between Vout and ground allows the EAMP to receive an outputfeedback voltage VFB at FB pin. When the load current increases, it causes a slightly decrease in VFB relative to the 0.8V reference, which in turn causes the COMP voltage to increase until the average inductor current matches the new load current.
VIN Power-On-Reset (POR)
The CXSD62225 keep monitoring the voltage on VIN pin to prevent wrong logic operations which may occur when VIN voltage is not high enough for the internal control circuitry to operate. The VIN POR has a rising threshold of 3.9V (typical) with 0.6V of hysteresis.After the VIN voltages exceed its respective POR thresholds,the IC starts a start-up process and then ramps up the output voltage to the setting of output voltage. Connect a RC network from EN to GND to set a turn-on delay that can be used to sequence the output voltages of multiple devices.
Enable/ShuJTMTown
Driving EN to ground places the CXSD62225 in shuJTMTown. When in shuJTMTown, the internal power MOSFETes turn off, all internal circuitry shuts down and the quiescent supply current of VlN reduces to<10μA, the EN under- voltage-lockout (UVLO) has a rising threshold of 1.4V(typical) with 0.2V of hysteresis.
Soft-Start
The CXSD62225 provides built-in soft-start function to limit the inrush current. The soft-start time is 1ms。
Bootstrap Capacitor
The CXSD62225 is a N-channel MOSFET step down converter.The MOSFET requires a gate voltage that is higher than input voltage, thus a boost capacitor should be connected between SW and BST pins to drive the gate of the N-channel MOSFET. Typical boostrap capacitor value is from 10nF to 100nF. 
Over-Current-Protection and Hiccup
The CXSD62225 has a cycle-by-cycle over-current limit when the inductor current peak value exceeds the set current limit threshold. Meanwhile, the output voltage drops until FB is below the Under-Voltage (UV) threshold below the reference. Once UV is triggered, the CXSD62225 enters hiccup mode to periodically restart the part. This protection mode is especially useful when the output is dead-shorted to ground. The average short circuit current is greatly reduced to alleviate thermal issues and to protect the regulator. The CXSD62225 exits the hiccup mode once the over-current condition is removed.
Over-Temperature Protection (OTP)
exceeds 150oC, a thermal sensor turns off the N-channel power MOSFET, allowing the device to cool down. The
thermal sensor allows the converter to start a start-up process and regulate the output voltage again after the
junction temperature cools by 30oC. The OTP designed with a 30oC hysteresis lowers the average TJ during continuous thermal overload conditions, increasing life time of the CXSD62225.
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