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I am looking to power a 5V system at roughly 600mA from a 6V AGM lead acid battery (voltage varies from 6V-6.3V). My main concern is finding a regulator that is tolerant enough to deal with the battery at full charge down to 50% charge without too much heat being generated. A quick search on linear technology's website yielded the LT1086, but the 1.5V max dropout has given me pause since I am unsure if the the NOCO Genius G750 Charger might bring the battery voltage higher. I am mainly looking for reliability with people that don't know much about electronics, so suggestions you have on picking a regulator would be appreciated.

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  • \$\begingroup\$ I think you misunderstand the term "dropout voltage". The 1.5 V max dropout voltage of the LT1086 means that the regulator is guaranteed to provide its rated output voltage provided that the input voltage is at least 1.5 volts higher than the output voltage. It will continue to regulate correctly with input voltages several volts higher than [output + 1.5V]. If the input voltage is less than 1.5 volts above the rated output voltage, the output voltage will drop, to maintain a 1.5 volt difference bewtween input and output voltages. \$\endgroup\$ – Peter Bennett Jun 4 '15 at 0:33
  • \$\begingroup\$ LDO or "Low Dropout" regulators are what you want. MANY available that meet your spec. | For a linera regulator power loss is (Vin-Vout) x Iload - this is the same with ANY linear regulaator. | LM29xx family probably meet your need. \$\endgroup\$ – Russell McMahon Jun 4 '15 at 1:31
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You need either a buck-boost switching regulator or a low-dropout regulator. The P-type output transistor of a LDO linear regulator gives a dropout measured in hundreds of millivolts versus a much higher dropout for linear regulators that use a N-type transistor instead. They are a bit more unstable though, so be sure to read the datasheet very carefully.

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