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The LP2951 regulator is manufactured by National Semiconductors. The choice of values is from an application note Battery Charging , written by Chester Simpson. Diode D1 can be any diode from the 1N00x series, whichever is conveniently available. It functions as a blocking diode, to prevent a back flow of current from the battery into the LP2951 when the input voltage is disconnected. Charging current is about 100+mA, which is the internally-limited maximum current of the LP2951. For those wondering, this is compatible with just about any single-cell li-ion battery since li-ion can generally accept a charging current of up to about 1c (i.e. charging current in mA equivalent to their capacity in mAh, so a 1100mAh li-ion cell can be charged at up to 1100mA and so on). Li-Ion Battery Charger Circuit Diagram A lower charging current just brings about a correspondingly longer charge time. IMHO 100mA is quite low, low enough that the circuit can be used for an overnight charger for many typ...

Li-Ion DRIVER WITH EXTERNAL PWM DIMMING ELECTRONIC DIAGRAM This boost converter is quite useful to improve conversion efficiency, reduce output ripple, and the use of small external components. In default, the LED current is set with external sensor resistor Rset, feed back voltage is regulated to 2000 miliVolts. During the operation, the current LED can be controlled using 1-wire digital interface through CTRL pin or with PWM signal that applied to the CTRL pin through the duty cycle. It determines the feedback reference voltage. The device also has a feature of integrated open LED protection that will disable the boost converter, this is to prevent the output from exceeding the absolute maximum ratings during open LED condition. L1: Murata LQH3NPN100NM0 C1: Murata GRM188R61A105K C2: Murata GRM188R61E474K D1: ONsemi MBR0540T1

Batteries often serve as the main energy source for portable electronic devices. Although they depend on batteries, portable consumer electronic products, such as GPS devices and multi-media players, often consume energy directly from an ac-dc wall adapter or accessory power adapter (or “Auto Adapter”) when the battery is low or the device is in a stationary mode. Due to their cost effectiveness over their useful life, rechargeable batteries are often used for the power source of the portable electronic device.   Attributes such as “relatively high energy density” and “maintenance free” make Lithium-Ion (Li-Ion) batteries popular in the portable consumer electronic products. Refer to the application note, AN1088, “Selecting the Right Battery System For cost Sensitive Portable Applications While maintaining Excellent Quality” (DS01088) for characteristics of Li-Ion batteries. Some examples of how to properly design with Li-Ion batteries will be discussed in this application note.