CXSD6293单相的时间恒定的同步的驱动N通道mosfet的PWM控制器满足低输出电压应用的要求

目录zsH嘉泰姆

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

一,产品概述(General Description)    zsH嘉泰姆

      The CXSD6293 is a single-phase, constant-on-time, and  synchronouszsH嘉泰姆
PWM controller, which drives N-channel MOSFETs. An internal 0.5V temperature-compensated reference voltage with high accuracy is designed to meet thezsH嘉泰姆
requirement of low output voltage applications. The CXSD6293 steps downzsH嘉泰姆
high voltage to generate low-volt-age chipset or RAM supplies in notebookzsH嘉泰姆
computers.The PWM controller operates fixed 300kHz pseudo-con-zsH嘉泰姆
stant frequency PWM with an adaptive constant-on-time control. The devicezsH嘉泰姆
provides excellent transient response and accurate DC voltage output in eitherzsH嘉泰姆
PFM or PWM Mode. In Pulse Frequency Mode (PFM), the CXSD6293 pro-zsH嘉泰姆
vides very high efficiency over light to heavy loads with loading-modulatedzsH嘉泰姆
switching frequencies. The device works in ultrasonic mode with PFM at nozsH嘉泰姆
load. The unique ultrasonic mode maintains the switching frequency abovezsH嘉泰姆
20kHz, which eliminates noise in audio applications.zsH嘉泰姆
          The CXSD6293 is equipped with accurate over-current,outputzsH嘉泰姆
under-voltage, and output over-voltage protections.A Power-On-ResetzsH嘉泰姆
function monitors the voltage on VCC to prevent wrong operation duringzsH嘉泰姆
power-on. The CXSD6293 has a 1.5ms digital soft-start to ramp up thezsH嘉泰姆
output voltage to reduce the start-up current. A soft-stop function activelyzsH嘉泰姆
discharges the output capacitors with controlled reverse inductor current.zsH嘉泰姆
The CXSD6293 is available in TDFN3x3-10 packagezsH嘉泰姆
二.产品特点(Features)zsH嘉泰姆

1.)Operates from An Input Battery Voltage Range of +3V to +25VzsH嘉泰姆
      ±0.6% 0.5V Reference Over Line, Load Regulation, andzsH嘉泰姆
      Operating Temp. zsH嘉泰姆
2.)Drive Dual Low Cost N-Channel MOSFETszsH嘉泰姆
    Adaptive Shoot-Through Protection zsH嘉泰姆
3.)Power-On-Reset Monitoring on VCC PinzsH嘉泰姆
4.)PFM Mode for Increasing Light Load EfficiencyzsH嘉泰姆
5.)Constant-On-Time Control SchemezsH嘉泰姆
     Switching Frequency Compensation for PWM OperationzsH嘉泰姆
6.)300kHz Constant Switching FrequencyzsH嘉泰姆
7.)Integrated MOSFET Drivers and Bootstrap DiodezsH嘉泰姆
8.)Internal Soft-Start and Soft-StopzsH嘉泰姆
9.)Power Good MonitoringzsH嘉泰姆
10.)70% Under-Voltage ProtectionzsH嘉泰姆
11.)125% Over-Voltage ProtectionzsH嘉泰姆
     Using Low-Side MOSFET’s RDS(ON)zsH嘉泰姆
12.)Over-Temperature ProtectionzsH嘉泰姆
13.)TDFN-10 3mmx3mm PackagezsH嘉泰姆
14.)Lead Free and Green Devices Available (RoHS Compliant)zsH嘉泰姆
三,应用范围 (Applications)zsH嘉泰姆

NotebookzsH嘉泰姆
Low Cost PCzsH嘉泰姆
Wide Input DC/DC RegulatorszsH嘉泰姆
四.下载产品资料PDF文档 zsH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！zsH嘉泰姆

 zsH嘉泰姆

五,产品封装图 (Package)zsH嘉泰姆

zsH嘉泰姆
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六.电路原理图zsH嘉泰姆

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七,功能概述zsH嘉泰姆

Constant-On-Time PWM Controller with Input Feed-For-wardzsH嘉泰姆
The constant-on-time control architecture is a pseudo-fixed frequency with input voltage feed-forward. This ar-zsH嘉泰姆
chitecture relies on the output filter capacitor’s effective series resistance (ESR) to act as a current-sense resis-zsH嘉泰姆
tor so the output ripple voltage provides the PWM ramp signal. In PFM operation, the high-side switch on-time iszsH嘉泰姆
controlled by the on-time generator is determined solely by a one-shot whose pulse width is inversely propor-zsH嘉泰姆
tional to the input voltage and directly proportional to the output voltage. In PWM operation, the high-side switchzsH嘉泰姆
on-time is determined by a switching frequency control circuit in the on-time generator block.The switchingzsH嘉泰姆
frequency control circuit senses the switch-ing frequency of the high-side switch and keeps regulat-zsH嘉泰姆
ing it at a constant frequency in PWM mode. The design improves the frequency variation and is more outstand-zsH嘉泰姆
ing than a conventional constant-on-time controller, which has large switching frequency variation over inputzsH嘉泰姆

 voltage,output current, and temperature. Both in PFM and PWM,the on-time generator, which senses input zsH嘉泰姆

voltage on PHASE pin, provides very fast on-time response to input line transients.Another one-shot sets a zsH嘉泰姆

minimum off-time (typical:300ns). The on-time one-shot is triggered if the error com-parator is high, thezsH嘉泰姆

 low-side switch current is below the current-limit threshold, and the minimum off-time one-shot has zsH嘉泰姆

timed out. zsH嘉泰姆
Pulse-Frequency Modulation (PFM)zsH嘉泰姆
In PFM mode, an automatic switchover to pulse-frequency modulation (PFM) takes place at light loads. ThiszsH嘉泰姆
switchover is affected by a comparator that truncates the low-side switch on-time at the inductor current zerozsH嘉泰姆
crossing. This mechanism causes the threshold between PFM and PWM operation to coincide with the boundaryzsH嘉泰姆
between continuous and discontinuous inductor-current operation (also known as the critical conduction point).zsH嘉泰姆
The on-time of PFM is given by:zsH嘉泰姆
Ultrasonic ModezsH嘉泰姆
The ultrasonic mode activates an unique PFM mode with a minimum switching frequency of 20kHz. The minimumzsH嘉泰姆
frequency 20kHz of ultrasonic mode eliminates audio-frequency interference in light load condition. It will transitzsH嘉泰姆
to unique PFM mode when output loading makes the frequency bigger than ultrasonic frequency.zsH嘉泰姆
In ultrasonic mode, the controller automatically transits to fixed-frequency PWM operation when the load reacheszsH嘉泰姆
the same critical conduction point (ILOAD(PFM to PWM)).When the controller detects that no switching has oc-zsH嘉泰姆
curred within about 40μs (Typical), an ultrasonic pulse will be occurred. The ultrasonic controller turns on thezsH嘉泰姆
low-side MOSFET firstly to reduce the output voltage. After feedback voltage drops below the internal referencezsH嘉泰姆
voltage, the controller turns off the low-side MOSFET and triggers a constant-on-time. When the constant-on-zsH嘉泰姆

time has expired, the controller turns on the low-side MOSFET again until the inductor current is below the zsH嘉泰姆

zero-cross-ing threshold. The behavior is the same as PFM mode. zsH嘉泰姆
Power-On-Reset (POR)zsH嘉泰姆
A Power-On-Reset (POR) function is designed to prevent wrong logic controls when the VCC voltage is low. ThezsH嘉泰姆
POR function continually monitors the bias supply volt-age on the VCC pin if at least one of the enable pins is setzsH嘉泰姆
high. When the rising VCC voltage reaches the rising POR voltage threshold (4.2V, typical), the POR signal goeszsH嘉泰姆
high and the chip initiates soft-start operations. When this voltage drops lower than 4.0V (typical), the POR dis-zsH嘉泰姆
ables the chip.zsH嘉泰姆

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