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1.产品概述                       2.产品特点Zo1嘉泰姆
3.应用范围                       4.下载产品资料PDF文档 Zo1嘉泰姆
5.产品封装图                     6.电路原理图                   Zo1嘉泰姆
7.功能概述                        8.相关产品Zo1嘉泰姆

七,功能概述Zo1嘉泰姆

Main Control LoopZo1嘉泰姆
The CXSD62144 is a constant frequency current mode switching regulator. During normal operation, the inter-Zo1嘉泰姆
nal N-channel power MOSFET is turned on each cycle when the oscillator sets an internal RS latch and wouldZo1嘉泰姆
be turned off when an internal current comparator (ICMP) resets the latch. The peak inductor current at which ICMPZo1嘉泰姆
resets the RS latch is controlled by the voltage on the COMP pin, which is the output of the error amplifierZo1嘉泰姆
(EAMP). An external resistive divider connected between VOUT and ground allows the EAMP to receive an outputZo1嘉泰姆
feedback voltage VFB at FB pin. When the load current increases, it causes a slight decrease in VFB relative toZo1嘉泰姆
the 0.925V reference, which in turn causes the COMP voltage to increase until the average inductor currentZo1嘉泰姆
matches the new load current.Zo1嘉泰姆
VIN Power-On-Reset (POR) and EN Under-voltage LockoutZo1嘉泰姆
The CXSD62144 keep monitoring the voltage on VIN pin to prevent wrong logic operations which may occur whenZo1嘉泰姆
VIN voltage is not high enough for the internal control circuitry to operate. The VIN POR has a rising thresholdZo1嘉泰姆
of 4.05V (typical) with 0.3V of hysteresis.Zo1嘉泰姆
An external under-voltage lockout (UVLO) is sensed atthe EN pin. The EN UVLO has a rising threshold of 2.5VZo1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 ENZo1嘉泰姆
voltages exceed their respective voltage thresholds, the IC starts a start-up process and then ramps up the outputZo1嘉泰姆
voltage to the setting of output voltage.Zo1嘉泰姆
Over-Temperature Protection (OTP)Zo1嘉泰姆
The over-temperature circuit limits the junction tempera-ture of the CXSD62144 When the junction temperature ex-Zo1嘉泰姆
ceeds TJ =+160oC, a thermal sensor turns off the power MOSFET, allowing the device to cool down. The thermalZo1嘉泰姆
sensor allows the converter to start a start-up process and regulate the output voltage again after the junctionZo1嘉泰姆
temperature cools by 50oC.Zo1嘉泰姆
The OTP designed with a 50 oC hysteresis lowers the average T J during c ontinuous thermal overload conditions,Zo1嘉泰姆
increasing life time of the IC.Zo1嘉泰姆
Enable/ShutdownZo1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.Zo1嘉泰姆
Current-Limit ProtectionZo1嘉泰姆
The CXSD62144 monitors the output current, flowing through the N-Channel power MOSFET, and limits theZo1嘉泰姆
IC from damages during overload, short-circuit and over-voltage conditions.Zo1嘉泰姆
Frequency FoldbackZo1嘉泰姆
The foldback frequency is controlled by the FB voltage.When the FB pin voltage is under 0.6V, the frequency ofZo1嘉泰姆
the oscillator will be reduced to 110kHz. This lower fre-quency allows the inductor current to safely discharge,Zo1嘉泰姆
thereby preventing current runaway. The oscillator’s fre-quency will switch to its designed rate when the feedbackZo1嘉泰姆
voltage on FB rises above the rising frequency foldback threshold (0.6V, typical) again.Zo1嘉泰姆
Over-Voltage ProtectionZo1嘉泰姆
The over-voltage function monitors the output voltage by FB pin. When the FB voltage increase over 120% of theZo1嘉泰姆
reference voltage, the over-voltage protection compara-tor will force the high-and low-side MOSFET gate driverZo1嘉泰姆
off. As soon as the output voltage is within regulation, the OVP comparator is disengaged. The chip will restore itsZo1嘉泰姆
normal operation.Zo1嘉泰姆
八,相关产品         更多同类产品.......Zo1嘉泰姆

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