电流源使线性稳压器提供更低的输出电压
传统上,由于体系结构对参考电压的依赖性,线性稳压器的输出电压仅限于参考电压。因此,由于旧一代架构采用1.2 V作为参考,这些稳压器的最小输出电压限制在1.2 V,系统板上的集成电路需要更低的电压来操作。因此,这些线性稳压器不能为需要小于1.2 V和更高电流的集成电路供电。
然而,一种新的线性稳压器结构克服了这种低输出电压限制。通过取代传统的电压参考电流源,新一代线性稳压器可以提供输出电压远低于1 V,事实上,它有能力去低至零伏特,根据制造商。此外,这种新的线性稳压器架构也可以配置为电流源。此外,不像旧一代线性稳压器,它可以并联,以提供更高的输出电流,如果需要的话。
Adjustable regulator
Linear Technology’s LT3081 and LT3082 incorporate the new architecture to deliver new levels of performance with adjustable output voltage that can be programmed down to 0 V at high current. While LT3081 is rated for 1.5 A output current capability, the LT3082 is a 200 mA low-dropout linear regulator.
As shown in Figure 1, a precision 50 μA reference current source connects to the non-inverting input of a power operational amplifier. The power operational amplifier provides a low-impedance buffered output to the voltage on the non-inverting input. A single resistor from the non-inverting input to ground sets the output voltage. If this resistor is set to 0 Ω, zero output voltage results. Therefore, any output voltage can be obtained between zero and the maximum defined by the input, which in the case of LT3081, is 40 V maximum. The Table lists many common output voltages that can be generated using the closest standard 1% resistor values for RSET.
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