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5 V Voltage Regulator

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What's a good voltage regulator for Vin of 4.8 - 6 with Vout of 5V? I've heard the 7805 really needs about 8V to work well also I'm not sure how efficient it is. I see the Digi-Key LDO #TK11650NT used in the pancam special project is no longer available.

Thanks.

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What's a good voltage regulator for Vin of 4.8 - 6 with Vout of 5V?

If the Vin is going to be lower than the output, then you'll need a DC-DC boost switcher. If your current demands are low, then perhaps something like this: http://www.dimensionengineering.com/AnyVoltMini.htm

However, if you can keep the Vin above 5.5VDC, then a typical LDO will work. Depending on your current requirements, the old LM2940T-5.0 may work out for you.

A basic VReg primer is found here: http://www.rc-cam.com/dc-dc.htm

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In that case, just find a 5V LDO with a very low dropout spec and just live with the reduced voltage when the Vin is at 4.8VDC. The TPS7250 or LP2951 would probably work fine for PanCam's PIC Vcc using a 4-cell NiCD or NIMH.

If you must ensure the Vreg voltage is perfectly 5VDC, then you need a 5-cell pack with this LDO. But, sometimes you can cheat. Especially in this case, since the PIC's current is just a couple mA's, which helps minimize the drop out impact.

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