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

七,功能概述qRr嘉泰姆

Main Control LoopqRr嘉泰姆
The CXSD62144 is a constant frequency current mode switching regulator. During normal operation, the inter-qRr嘉泰姆
nal N-channel power MOSFET is turned on each cycle when the oscillator sets an internal RS latch and wouldqRr嘉泰姆
be turned off when an internal current comparator (ICMP) resets the latch. The peak inductor current at which ICMPqRr嘉泰姆
resets the RS latch is controlled by the voltage on the COMP pin, which is the output of the error amplifierqRr嘉泰姆
(EAMP). An external resistive divider connected between VOUT and ground allows the EAMP to receive an outputqRr嘉泰姆
feedback voltage VFB at FB pin. When the load current increases, it causes a slight decrease in VFB relative toqRr嘉泰姆
the 0.925V reference, which in turn causes the COMP voltage to increase until the average inductor currentqRr嘉泰姆
matches the new load current.qRr嘉泰姆
VIN Power-On-Reset (POR) and EN Under-voltage LockoutqRr嘉泰姆
The CXSD62144 keep monitoring the voltage on VIN pin to prevent wrong logic operations which may occur whenqRr嘉泰姆
VIN voltage is not high enough for the internal control circuitry to operate. The VIN POR has a rising thresholdqRr嘉泰姆
of 4.05V (typical) with 0.3V of hysteresis.qRr嘉泰姆
An external under-voltage lockout (UVLO) is sensed atthe EN pin. The EN UVLO has a rising threshold of 2.5VqRr嘉泰姆
with 0.2V of hysteresis. The EN pin should be connected a resistor divider from VIN to EN .After the VIN and ENqRr嘉泰姆
voltages exceed their respective voltage thresholds, the IC starts a start-up process and then ramps up the outputqRr嘉泰姆
voltage to the setting of output voltage.qRr嘉泰姆
Over-Temperature Protection (OTP)qRr嘉泰姆
The over-temperature circuit limits the junction tempera-ture of the CXSD62144 When the junction temperature ex-qRr嘉泰姆
ceeds TJ =+160oC, a thermal sensor turns off the power MOSFET, allowing the device to cool down. The thermalqRr嘉泰姆
sensor allows the converter to start a start-up process and regulate the output voltage again after the junctionqRr嘉泰姆
temperature cools by 50oC.qRr嘉泰姆
The OTP designed with a 50 oC hysteresis lowers the average T J during c ontinuous thermal overload conditions,qRr嘉泰姆
increasing life time of the IC.qRr嘉泰姆
Enable/ShutdownqRr嘉泰姆
Driving EN to ground places the CXSD62144 in shutdown.When in shutdown, the internal N-Channel power MOSFET turns off, all internal circuitry shuts down and the quies-cent supply current reduces to 0.3μA.qRr嘉泰姆
Current-Limit ProtectionqRr嘉泰姆
The CXSD62144 monitors the output current, flowing through the N-Channel power MOSFET, and limits theqRr嘉泰姆
IC from damages during overload, short-circuit and over-voltage conditions.qRr嘉泰姆
Frequency FoldbackqRr嘉泰姆
The foldback frequency is controlled by the FB voltage.When the FB pin voltage is under 0.6V, the frequency ofqRr嘉泰姆
the oscillator will be reduced to 110kHz. This lower fre-quency allows the inductor current to safely discharge,qRr嘉泰姆
thereby preventing current runaway. The oscillator’s fre-quency will switch to its designed rate when the feedbackqRr嘉泰姆
voltage on FB rises above the rising frequency foldback threshold (0.6V, typical) again.qRr嘉泰姆
Over-Voltage ProtectionqRr嘉泰姆
The over-voltage function monitors the output voltage by FB pin. When the FB voltage increase over 120% of theqRr嘉泰姆
reference voltage, the over-voltage protection compara-tor will force the high-and low-side MOSFET gate driverqRr嘉泰姆
off. As soon as the output voltage is within regulation, the OVP comparator is disengaged. The chip will restore itsqRr嘉泰姆
normal operation.qRr嘉泰姆
八,相关产品         更多同类产品.......qRr嘉泰姆

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