Need a little help here. I am looking for a LDO DC/DC Converter. I have 7.5V input, looking for 5V output. Total current output needs to be upwards of 1A. Power consumption is critical and must be as low as possible since the 7.5V is from batteries. For this reason I have had a hard time finding an appropriate part. Any ideas?
Cheers, Mike
If power consumption is critical, you need a step-down (buck) switching regulator. Don't look for "low dropout" parts because that concept only makes sense for linear regulators.
There are scores of ICs that can do what you want. Linear Technology's is a website you might want to start at.
robert
Right. Under "dropout" conditions the switch in an ideal buck regulator simply stays on all the time. Assuming it's a MOSFET, the value of Rds(on) for the gate-drive condition at the input dropout voltage will determine the input-output voltage drop. You can select a larger MOSFET to reduce the drop if you wish.
If the pass-switch is a BJT, its saturation voltage at the load current will determine the dropout voltage. Some regulators use up a small additional drop for a current-sensing function.
As well as all the other usual suspects.
Take a look at the National Semiconductor LM2575 (1-Amp) or the LM2576 (3-Amp)
I've used the 2575. (9-pin TO-220 package) It requires an inductor, a Shottkey diode, and input/output caps. So you're looking at a 5-component solution if you go that route.
My guess is the 2576 requires a pass transistor, but I don't know that for certain.
Good luck.
-mpm
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