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1.产品概述                       2.产品特点xR6嘉泰姆
3.应用范围                       4.下载产品资料PDF文档 xR6嘉泰姆
5.产品封装图                     6.电路原理图                   xR6嘉泰姆
7.功能概述                        8.相关产品xR6嘉泰姆

七,功能概述xR6嘉泰姆

Main Control LoopxR6嘉泰姆
The CXSD62144 is a constant frequency current mode switching regulator. During normal operation, the inter-xR6嘉泰姆
nal N-channel power MOSFET is turned on each cycle when the oscillator sets an internal RS latch and wouldxR6嘉泰姆
be turned off when an internal current comparator (ICMP) resets the latch. The peak inductor current at which ICMPxR6嘉泰姆
resets the RS latch is controlled by the voltage on the COMP pin, which is the output of the error amplifierxR6嘉泰姆
(EAMP). An external resistive divider connected between VOUT and ground allows the EAMP to receive an outputxR6嘉泰姆
feedback voltage VFB at FB pin. When the load current increases, it causes a slight decrease in VFB relative toxR6嘉泰姆
the 0.925V reference, which in turn causes the COMP voltage to increase until the average inductor currentxR6嘉泰姆
matches the new load current.xR6嘉泰姆
VIN Power-On-Reset (POR) and EN Under-voltage LockoutxR6嘉泰姆
The CXSD62144 keep monitoring the voltage on VIN pin to prevent wrong logic operations which may occur whenxR6嘉泰姆
VIN voltage is not high enough for the internal control circuitry to operate. The VIN POR has a rising thresholdxR6嘉泰姆
of 4.05V (typical) with 0.3V of hysteresis.xR6嘉泰姆
An external under-voltage lockout (UVLO) is sensed atthe EN pin. The EN UVLO has a rising threshold of 2.5VxR6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 ENxR6嘉泰姆
voltages exceed their respective voltage thresholds, the IC starts a start-up process and then ramps up the outputxR6嘉泰姆
voltage to the setting of output voltage.xR6嘉泰姆
Over-Temperature Protection (OTP)xR6嘉泰姆
The over-temperature circuit limits the junction tempera-ture of the CXSD62144 When the junction temperature ex-xR6嘉泰姆
ceeds TJ =+160oC, a thermal sensor turns off the power MOSFET, allowing the device to cool down. The thermalxR6嘉泰姆
sensor allows the converter to start a start-up process and regulate the output voltage again after the junctionxR6嘉泰姆
temperature cools by 50oC.xR6嘉泰姆
The OTP designed with a 50 oC hysteresis lowers the average T J during c ontinuous thermal overload conditions,xR6嘉泰姆
increasing life time of the IC.xR6嘉泰姆
Enable/ShutdownxR6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.xR6嘉泰姆
Current-Limit ProtectionxR6嘉泰姆
The CXSD62144 monitors the output current, flowing through the N-Channel power MOSFET, and limits thexR6嘉泰姆
IC from damages during overload, short-circuit and over-voltage conditions.xR6嘉泰姆
Frequency FoldbackxR6嘉泰姆
The foldback frequency is controlled by the FB voltage.When the FB pin voltage is under 0.6V, the frequency ofxR6嘉泰姆
the oscillator will be reduced to 110kHz. This lower fre-quency allows the inductor current to safely discharge,xR6嘉泰姆
thereby preventing current runaway. The oscillator’s fre-quency will switch to its designed rate when the feedbackxR6嘉泰姆
voltage on FB rises above the rising frequency foldback threshold (0.6V, typical) again.xR6嘉泰姆
Over-Voltage ProtectionxR6嘉泰姆
The over-voltage function monitors the output voltage by FB pin. When the FB voltage increase over 120% of thexR6嘉泰姆
reference voltage, the over-voltage protection compara-tor will force the high-and low-side MOSFET gate driverxR6嘉泰姆
off. As soon as the output voltage is within regulation, the OVP comparator is disengaged. The chip will restore itsxR6嘉泰姆
normal operation.xR6嘉泰姆
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