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目录3Zl嘉泰姆

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

一,产品概述(General Description)      3Zl嘉泰姆

                The CXSD6279B is a voltage mode and synchronous PWM controller3Zl嘉泰姆
which drives dual N-Channel MOSFETs. It inte-grates the control, monitoring,3Zl嘉泰姆
and protection functions into a single package, provides one controlled power3Zl嘉泰姆
outputs with under-voltage and over-current protection.CXSD6279B provides3Zl嘉泰姆
excellent regulation for output load variation. An internal 0.8V temperature-3Zl嘉泰姆
compensated reference voltage is designed to meet the requirement of3Zl嘉泰姆
low output voltage applications. It includes a 200kHz free-running3Zl嘉泰姆
triangle-wave oscillator that is adjustable from 70kHz to 800kHz.3Zl嘉泰姆
        The power-on-reset (POR) circuit monitors the VCC, EN,and OCSET3Zl嘉泰姆
input voltage to start-up or shutdown the IC.The over-current protection (OCP)3Zl嘉泰姆
monitors the output current by using the voltage drop across the upper3Zl嘉泰姆
MOSFET’s RDS(ON), eliminating the need for a current sens-ing resistor.3Zl嘉泰姆
The under-voltage protection (UVP) moni-tors the voltage of the FB pin for3Zl嘉泰姆
short-circuit protection.The over-current protection trip cycle the soft-start3Zl嘉泰姆
func-tion until the fault events be removed. Under-voltage pro-tection will3Zl嘉泰姆
shutdown the IC directly.3Zl嘉泰姆
二.产品特点(Features)3Zl嘉泰姆

1.)Simple Single-Loop Control Design3Zl嘉泰姆
   Voltage-Mode PWM Control3Zl嘉泰姆
2.)Fast Transient Response3Zl嘉泰姆
    Full 0–100% Duty Ratio3Zl嘉泰姆
3.)Excellent Output Voltage Regulation3Zl嘉泰姆
   0.8V Internal Reference3Zl嘉泰姆
    ± 1% Over Line Voltage and Temperature3Zl嘉泰姆
4.)Over Current Fault Monitor3Zl嘉泰姆
   Uses Upper MOSFETs RDS (ON)3Zl嘉泰姆
5.)Converter Can Source and Sink Current3Zl嘉泰姆
6.)Small Converter Size3Zl嘉泰姆
    200kHz Free-Running Oscillator3Zl嘉泰姆
   Programmable from 70kHz to 800kHz3Zl嘉泰姆
7.)14-Lead SOIC Package3Zl嘉泰姆
8.)Lead Free and Green Devices Available (RoHS Compliant)3Zl嘉泰姆
三,应用范围 (Applications)3Zl嘉泰姆

Graphic Cards3Zl嘉泰姆
DDR Memory Power Supply3Zl嘉泰姆
DDR Memory Termination Voltage3Zl嘉泰姆
Low-Voltage Distributed Power Supplies3Zl嘉泰姆
四.下载产品资料PDF文档 3Zl嘉泰姆

需要详细的PDF规格书请扫一扫微信联系我们，还可以获得免费样品以及技术支持！3Zl嘉泰姆

 3Zl嘉泰姆

五,产品封装图 (Package)3Zl嘉泰姆

3Zl嘉泰姆
RT (Pin1)3Zl嘉泰姆
This pin can adjust the switching frequency. Connect a resistor from the RT to the GND for increasing the switch-3Zl嘉泰姆
OCSET (Pin2)3Zl嘉泰姆
This pin serves two functions: a shutdown control and the setting of over current-limit threshold. Pulling this pin3Zl嘉泰姆
below 1.27V will shutdown the controller, forcing the UGATE and LGATE signals to be at 0V.3Zl嘉泰姆
A resistor (Rocset) connected between this pin and the drain of the high side MOSFET will determine the over 3Zl嘉泰姆

current limit. An internal 200μA current source will flow through this resistor, creating a voltage drop, which 3Zl嘉泰姆

will be com-pared with the voltage across the high side MOSFET.3Zl嘉泰姆
SS (Pin3)3Zl嘉泰姆
Connect a capacitor from the pin to the GND to set the soft-start interval of the converter. An internal 10μA 3Zl嘉泰姆

current source charges this capacitor to 5.8V. The SS voltage clamps the error amplifier output, and Figure13Zl嘉泰姆

 shows the soft-start interval. At t1, the SS voltage reaches the valley of the oscillator’s triangle wave. The3Zl嘉泰姆

PWM comparator starts to generate a PWM signal to control logic, and the3Zl嘉泰姆
COMP (Pin4)3Zl嘉泰姆
This pin is the output of the error amplifier. Add an exter-nal resistor and capacitor network to provide the3Zl嘉泰姆

 loop com- pensation for the PW M converter (see Application Information).3Zl嘉泰姆
FB (Pin5)3Zl嘉泰姆
FB pin is the inverter input of the error amplifier and it receives the feedback voltage from an external 3Zl嘉泰姆

resis-tive divider across the output (V OUT). The output voltage is determined by:3Zl嘉泰姆
EN (Pin6)3Zl嘉泰姆
Pull the pin higher than 2V to enable the device, and pull the pin lower than 0.8V to shutdown the 3Zl嘉泰姆

device. In shutdown, the SS is discharged and the UGATE and LGATE pins are held low. The EN pin 3Zl嘉泰姆

is the open-collector, and it will not be floating. 3Zl嘉泰姆
GND (Pin7)3Zl嘉泰姆
Signal ground for the IC. 3Zl嘉泰姆
PHASE (Pin8)3Zl嘉泰姆
This pin is connected to the source of the high-side MOSFET and is used to monitor the voltage drop3Zl嘉泰姆

 across the high-side MOSFET for over-current protection. 3Zl嘉泰姆
UGATE (Pin9)3Zl嘉泰姆
Connect the pin to external MOSFET, and provides the gate drive for the upper MOSFET.3Zl嘉泰姆

BOOT (Pin 10)3Zl嘉泰姆
This pin provides the supply voltage to the high side MOSFET driver. For driving logic level N-channel 3Zl嘉泰姆

MOSEFT,a bootstrap circuit can be used to create a suitable driver’s supply. 3Zl嘉泰姆
PGND (Pin11)3Zl嘉泰姆
Power ground for the gate diver. Connect the lower MOSFET source to this pin. 3Zl嘉泰姆
LGATE (Pin 12)3Zl嘉泰姆

Connect the pin to the external MOSFET, and provides the gate drive signal for the lower MOSFET.3Zl嘉泰姆
PVCC (Pin13)3Zl嘉泰姆
This pin provides a supply voltage for the lower gate drive, connect it to the VCC pin in common use. 3Zl嘉泰姆
VCC (Pin14)3Zl嘉泰姆
This pin provides a supply voltage for the device. When the VCC is above the rising threshold 10.4V, 3Zl嘉泰姆

the device is turned on; conversely, when the VCC is below the falling threshold, the device is turned off.3Zl嘉泰姆
六.电路原理图3Zl嘉泰姆

3Zl嘉泰姆
七,功能概述3Zl嘉泰姆

Output Capacitor Selection3Zl嘉泰姆
The selection of COUT is determined by the required effec-tive series resistance (ESR) and voltage rating3Zl嘉泰姆

 rather than the actual capacitance requirement. Therefore, select highperformance low ESR capacitors 3Zl嘉泰姆

that are intended for switching regulator applications. In some applications,multiple capacitors have to3Zl嘉泰姆

 be paralled to achieve the desired ESR value. If tantalum capacitors are used, makesure they are surge3Zl嘉泰姆

 tested by the manufactures. If in doubt,consult the capacitors manufacturer.3Zl嘉泰姆
 Input Capacitor Selection3Zl嘉泰姆
The input capacitor is chosen based on the voltage rating and the RMS current rating. For reliable 3Zl嘉泰姆

operation, select the capacitor voltage rating to be at least 1.3 times higher than the maximum input3Zl嘉泰姆

 voltage. The maximum RMS current rating requirement is approximately IOUT/2 , where IOUT is the 3Zl嘉泰姆

load current. During power up, the input capaci-tors have to handle large amount of surge current.3Zl嘉泰姆

 If tanta-lum capacitors are used, make sure they are surge tested by the manufactures. If in doubt, 3Zl嘉泰姆

consult the capacitors manufacturer.For high frequency decoupling, a ceramic capacitor be-tween3Zl嘉泰姆

 0.1μF to 1μF can be connected between the VCC and the ground pin.3Zl嘉泰姆
Inductor Selection3Zl嘉泰姆
The inductance of the inductor is determined by the out-put voltage requirement. The larger the 3Zl嘉泰姆

inductance, the lower the inductor’s current ripple. This will translate into lower output ripple voltage.3Zl嘉泰姆

 The ripple current and ripple voltage can be approximated by:3Zl嘉泰姆
where Fs is the switching frequency of the regulator.There is a tradeoff exists between the inductor’s3Zl嘉泰姆

 ripple current and the regulator load transient response time. A smaller inductor will give the regulator 3Zl嘉泰姆

a faster load tran-sient response at the expense of higher ripple current and vice versa. The maximum3Zl嘉泰姆

 ripple current occurs at the maximum input voltage. A good starting point is to choose the ripple 3Zl嘉泰姆

current to be approximately 30% of the maxi-mum output current.Once the inductance value has 3Zl嘉泰姆

been chosen, select an inductor that is capable of carrying the required peak cur-rent without going 3Zl嘉泰姆

into saturation. In some types of inductors, especially core that is make of ferrite, the ripple3Zl嘉泰姆
current will increase abruptly when it saturates. This will result in a larger output ripple voltage.3Zl嘉泰姆
Compensation3Zl嘉泰姆
The output LC filter introduces a double pole, which con-tributes with –40dB/decade gain slope and 3Zl嘉泰姆

180 degrees phase shift in the control loop. A compensation network between the COMP pin and the 3Zl嘉泰姆

ground should be added. The simplest loop compensation network is shown in3Zl嘉泰姆
Figure 5.3Zl嘉泰姆
The output LC filter consists of the output inductor and output capacitors. The transfer function of3Zl嘉泰姆

 the LC filter is given by:3Zl嘉泰姆
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