DS215GHDQG5AZZ01 PLC工控备件
双极性输出电压感测
对于负输出应用，FB引脚通常保持打开状态。双极性输出电压感测某些应用受益于感测正和负输出电压。典型应用部分中所示的“带过电压保护的双输出反激转换器”电路就是一个例子。每个输出电压电阻器分压器如上所述单独设置。当使用FB和NFB引脚时，R1 VOUT=VREF 1+R2 FB引脚VREF VOUT（）R1 R2 R1=R2–1（）VOUT 1.245 LT1370•F01 APPLICATIO S I FOR ATIO UU W U图1。正输出电阻分压器LT1370用于防止任一输出超过其设定输出电压。例如，在该应用中，如果正输出比负输出负载更重，则负输出将更大，并将调节到期望的设定点电压。正输出将略低于其设定点电压。该技术可防止任何一个输出在无负载时变为未调节的高电平。
负输出电阻分压器
R1–VOUT=VNFB+I 1+NFB（R1）R2 LT1370•F02 NFB PIN VNFR INFB–VOUT（）R1 R2 R1=+30•10–6⏐v.保证⏐– 2.48（）（）2.48 R2 OPERATION U 8 LT1370 sn1370 1370fs关机和同步设备具有双功能S/S引脚，用于关机和同步。该引脚与逻辑电平兼容，可以拉高、连接到VIN或保持浮动以正常工作。S/S引脚上的逻辑低激活关机，将部件的电源电流降至12µA。典型的同步范围是部件自然开关频率的1.05到1.8倍，但仅保证在600kHz和800kHz之间。12µs可复位停机延迟网络可确保部件在收到同步信号时不会停机。当同步频率高于700kHz时应小心，因为在较高的同步频率下，用于防止次谐波切换的内部斜率补偿的幅度会降低。这种类型的次谐波切换仅在开关的占空比高于50%时发生。
Bipolar output voltage sensing
For negative output applications, the FB pin usually remains open. Bipolar output voltage sensing Some applications benefit from sensing positive and negative output voltages. The circuit of "dual output flyback converter with overvoltage protection" shown in the typical application section is an example. Each output voltage resistor divider is set separately as described above. When FB and NFB pins are used, R1 VOUT=VREF 1+R2 FB pin VREF VOUT() R1 R2 R1=R2 – 1 () VOUT 1.245 LT1370 • F01 APPLICATIO S I FOR ATIO UU W U Fig. 1. The positive output resistance voltage divider LT1370 is used to prevent any output from exceeding its set output voltage. For example, in this application, if the positive output is heavier than the negative output load, the negative output will be larger and will be adjusted to the desired setpoint voltage. The positive output will be slightly below its set point voltage. This technology can prevent any output from becoming an unregulated high level when there is no load.
Negative output resistance voltage divider
R1–VOUT=VNFB+I 1+NFB（R1）R2 LT1370•F02 NFB PIN VNFR INFB–VOUT（）R1 R2 R1=+30•10–6⏐v. Ensure that the ⏐ - 2.48 () () 2.48 R2 OPERATION U 8 LT1370 sn1370 1370fs shutdown and synchronization device has a dual function S/S pin for shutdown and synchronization. This pin is compatible with the logic level and can be pulled up, connected to the VIN, or held floating for normal operation. The logic low on the S/S pin activates the shutdown, reducing the power current of the component to 12 µ A. The typical synchronization range is 1.05 to 1.8 times of the component's natural switching frequency, but only between 600kHz and 800kHz. The 12 µ s resettable shutdown delay network ensures that the component does not shut down when it receives a synchronization signal. Be careful when the synchronous frequency is higher than 700kHz, because the amplitude of internal slope compensation used to prevent subharmonic switching will decrease at a higher synchronous frequency. This type of subharmonic switching only occurs when the duty cycle of the switch is higher than 50%.
