This application note explains about various contributors to battery capacity consumption in a battery backed application, and how to predict battery lifetime in a system. The issues about how to predict the battery lifetime is eplained in detail in Sample Lifetime Calculations section. This application note is divided into 7 section: Why Battery Backup?, IC Current Demands, Battery Construction/Attributes, Battery Testing/Screening, Sample Lifetime Calculations, Integrated Battery Controllers, Battery Module Products, and Conclusion.

Why battery backup? section talks about the reason why need battery backup, Battery-backed SRAMs, and disadvantage of battery-backed SRAM. The explaination about the IC (SRAM or RTC) current demand, battery-backed products, and battery capacities are described in the section IC Current Demands. The section Battery construction/Attributes explains about primary lithium coin-cell batteries, construction of the battery, voltage Distributions and  indication of an abnormal IC or battery.

The description about Battery Testing, battery Screening, visual sampling of the batteries, and internal leakage of the battery are explained in detail in section Battery Testing/Screening. Battery Reliability Model section talks about balanced construction, The key components, The reliability model and Calculating the lifetime of the battery. The example of how to predict lifetime is talked in Sample Lifetime Calculations section. The issues about battery controller, standalone battery controllers, and lithium battery construction are described in Integrated Battery Controllers section. The Battery Module Products and conclusion section talks about module product that contains the battery controller and battery,  “Sleep Mode” function and the conclusion of this application note.

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This application note talks about reducing PCB costs from schematic capture to PCB layout. The issues about how to reduce the cost of PCB designs is explained in detail in this note. This application note is divided into 5 section: The basics, Schematic libraries, PCB libraries, The netlist file, and  Save time and avoid errors.

The section the basics tells about schematic capture packages, PCB layout packages, and design rules. The symbol libraries, schematic library, footprint attribute, user library and schematic capture tool are described in section schematic libraries. The section PCB libraries explains about PCB libraries, the footprints designated by industry standard, surface-mount through-hole devices, decal, pads, and electrical pin number. The explaination about netlist file, schematic databases, PCB databases, error in processing netlist file, rubber band information, and PCB routing are described in detail in section the netlist file. The save time and avoid errors section talks about how to avoid the erors, the back-annotation, and verification of the schematic and board files.

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This is a circuit for 12V – 4A Power Supply. This circuit uses BD705 and L200. To regulate the output voltage this circuit use the 3.3 k resistor and the 1K potentiometer, PT1. Here is the circuit :

From the second figure, we can see the current limitation of this circuit. The trimmer PT2 works on strech AB of characteristic. The current from 3 to 4 A can be limited by using the given values (R=3k, PT2=1k, PT3=470 ohm). connecting one terminal of PT to the power transistor’s base or increase the Rsc’s values will increase the field of variation. But, the stable limitation will decrease. The section BC will be move, if section AB is moved.

The PT3 can be used to vary the slope BC. The zener diode’s voltage is used to fix the voltage level at point B. Together with capacitor in parallel connection, it will ensure correct switch-on with full load.

The last figure shows the addition protection for the external power transistor. The prevention of the Tj of the power transistor from reaching its maximum value is done by the PTC resistor that should be fixed to the dissipator near the power transistor. Selecting PTC will affect dimensioning of RB and RA. [STMicroelectronics Application Note]

This  Analog Applications Journal talks about Noise in an LDO, the type of noise, and power supply ripple rejection (PSRR). The issues about noise in analog circuits is explained in detail in this note. The description LDO application is also described in this note. This analog applications journal also talks about the simplified block diagram, the closed-loop gain of an LDO and equivalent series resistance (ESR). The note presents the explaination of primary noise sources in an LDO, thermal noise, and noise reduction in LDO application.

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