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Battery Switch With Low-Dropout Regulator(LT1579)

2015-09-19 01:39  
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This article briefly describes Battery Switch With Low-Dropout Regulator (LT1579). This principle is easy to understand, but also very practical. Depth understanding of circuit elements, you can better grasp this principle. In this circuit, you can learn about and purchase these components: LT1579.

In the form of the LT1579 Linear Technology (http://www.linear-tech.com) has produced a practical battery switch with an integrated low-dropout regulator. In contrast to previous devices no diodes are required. The circuit is available in a 3.3 V version (LT1579CS8-3.3) and in a 5 V version (LT1579CS8-5), both in SO8SMDpackages. There is also an adjustable version and versions in an SO16 package which offer a greater range of control and drive signals. The main battery, whose terminal voltage must be at least 0.4 V higher than the desired output voltage, is connected to pin IN1. The backup battery is connected to pin IN2. The regulated outputOUTcan deliver a current of up to 300 mA. TheLDOregulator part of the IC includes a pass transistor for the main input voltage IN1 and another for the backup battery on IN2.


Figure 1 

The IC will switch over to the backup battery when it detects that the pass transistor for the main voltage input is in danger of no longer being able to maintain the required output voltage. The device then smoothly switches over to the backup battery. The open-drain status outputBACKUPgoes low to indicate when this has occurred. When neither battery is able to maintain the output voltage at the desired level the open-drain outputDROPOUTgoes low. The LT1579 can operate with input voltages of up to 20 V from the batteries. The regulator outputOUTis short-circuit proof. The shutdown input switches off the output; if this feature is not required, the input can simply be left open.



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