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Electronics projects

Last update: 31/07/2015

Sometimes we need to power an electronic project (using picmicro, for instance) powering it with a voltage of 3.3 or 5V but we have a source of 1.2-2.4 V give by one or two batteries. There are two solution to this problem: increase the number of the batteries or use a particular switching IC to increase the value of the voltage.

 

On the market there are hundreds od step-up ICs but one of them, quite cheap, very simple to implement, using a limited external circuitery, easily available is the Linear Technology LT1300.

This IC works with a minimal input voltage of 1.8V and provides more than 200mA at 5V (while the LT1301 provides 12V with an input voltage of 3.3 or 5V). Pratically it is perfect to power a microcontrolled device.

Schematic is really simple: The image (from the LT1300 appl.note)

LT1300 

When the Shutdown pin is taken high the device is disabled and the power consuption reach only 10uA (only 140uA during the use).

The select pin high set the voltage of the output at 5V, 3.3 if grounded.

The I-lim pin grounded limits the max current to 400ma

As we can see, the circuit uses a very small inductor of 10uH, a schottky diode and a couple of capacitors, nothing more.

necessaria al funzionamentoe' limitata ad un induttore (molto piccolo, peraltro), un paio di condensatori ed un diodo schottky.

 

Another very interesting (but surface mount) component is made by Texas Instruments: the TPS61220 (or 1-2 final). 

TPS61220

The circuitry in this case is even simpler. It provides an output of 200ma at 5V starting from a cell or two (nicd, nimh or alkaline). A couple of small capacitors (10uf, ceramic) and a small inductor (4.7mH) will complete the circuit.


Such a circuit (very popular for remote control) are absolutely necessary when we need to power an electronic device using a very limited power supply given by a single or a double cell. They work very precisely and the stand-by current is always very limited. All catalogs of ic houses have a lot of such integrated circuits in theyr catalogue with different characteristics and power. 

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