UC3843- PWM Controller IC (8-Pin)

2 July 2018 - 0 Comments

UC3843 PWM控制器IC

UC3843 PINOUT

Note:This IC also comes in 14-Pin, 16-Pin and 20-Pin packages. This article covers only on the 8-Pin version of the IC.

引脚配置

Pin Number	Pin Name	描述
1	comp（比较器）	它是一个输出接脚输出低的小鬼ance 1MHz single based in the difference between he set and current voltage. It is normally connected to the voltage feedback pin of the IC through resistor and capacitor.
2	VFB (Voltage Feedback)	它是IC内部的错误放大器的输入。电压水平的差异提供给此PIN
3	Current Sense	A shunt resistor is used to monitor the current through the circuit and the voltage across it is provided as a feedback to the current sense pin
4	RT/ CT（正时电阻/正时电容器）	IC具有内部振荡器，可以使用连接到该引脚的外部电阻和电容器来设置该振荡器。
5	地面	Connected to the ground of the circuit
6	Output	This pin outputs the PWM signal based on the feedback provided and we can use this to switch the power electronic device.
7	VCC	Supply voltage for the IC (Nominal 11V)
8	VREF	基于产生PWM信号的参考电压。

UC3843Specifications

电流模式PWM控制器
Operating Voltage: 7.0V to 8.2V
Output pin current: 1A
模拟输入范围：-0.3至6.3V
振荡频率：52通常
Gain: 3V
Maximum source current: 22mA
Low Output Voltage: 0.08V
高输出电压：13.5V

UC3843Equivalent/Substitute

UC3842

Alternatives PWM controller ICs

UC2842, UC3842, UC3844, SG2524

Where to use the UC3843 PWM Controller IC

TheUC3843 ICis a当前模式PWM控制器, meaning it can be used to provide a constant current by varying the output voltage to the load. While building Switch mode supplies with feedback there are two modes of control that is commonly used, one is voltage mode control where the output voltage will kept constant irrespective of the current (CV mode) and the other is current mode control where the output current will be constant (C mode) irrespective of the voltage.

TheUC3843can be used to调节或限制电流在应用中SMPS.,rps.,DC-DC Converters,线电压调节器等等。因此，如果您正在寻找一个IC来产生PWM信号，以根据电路流过电流来控制电源开关，那么此IC可能是您的正确选择。

How o use UC3843 IC

Although the IC performs a sophisticated job, using it in a circuit is fairly simple and can be done with minimum number if external components which make this IC to be a preferable choice among designers. A sample application circuit of this IC is shown below.

UC3843PWM控制器Circuit

The IC has an under voltage protection, so care should be taken to make sure that it has an operating voltage between 7V to 8.2V. The output pin of the IC is connected to the gate driver circuit of the Power switch which is to be switched. The output pin can source upto 1A ad hence a current limiting resistor will be required. The VFB (Voltage feedback) pin acts as a feedback based on which the PWM signal is controlled. A shunt resistor is used to monitor the change in current in the circuit and then this difference voltage across the shunt is provided to the feedback pin.

The IC also has an internal oscillator which can be configured using by connecting the right value of capacitor and resistor to the pin Rt/Ct. The Datasheet recommends a value of between 470pf to 4.7nf and for the resistor a value between 5k to 100k. Refer the datasheet at the end of the page to know more about this IC. Also check out the Layout diagram at the bottom of the datasheet for a quick start. A more detailed application circuit is shown below.

UC3843Application Circuit Diagram