Electronic – buck-boost, SEPIC IC out 3.3V and min 500mA 0.1″ packaging

boostbuckintegrated-circuitpinoutvoltage-regulator

I am building some sort of navigation device for a logisitics project in my company.
The whole thing is going to be battery (6V) powered, so I'm looking for every possible way to avoid losses to heat etc by turning off ports I don't need, stripping peripherals etc..
My lineup so far is a Rapsberry Pi A (40% less consumption than ver. B), a 128 x 64 px touch display that comes with some nice power-down features and an XBee-Pro module, that also has sleep and hibernate modes.

All these devices run on 3.3V. The 5V on the Pi are only used to power the attachable USB devices, so the input to the Pi is regulated to 5V if it is above, then fed to the USBs and again regulated to 3.3V. Both regulations happening with linear regulators afaik, which are not very efficient, aka they just "burn" the undesired amount of V.

Now if I disable the integrated regulators of the Pi and attach my own buck-boost/SEPIC ICs regulator that goes straight and efficient from Vin to my desired 3.3V I can again save a lot of energy.

My problem: I cannot seem to find a suitable chip. The main difficulty is that those I was able to find ususally come in a packaging type that is impossible for human hands to solder.
I am looking for:

  • Vin up to 7V
  • Iout at least 500mA
  • Vout 3.3V
  • buck-boost mode
  • 0.1" pin-out

Any help apprechiated!

schematic

simulate this circuit – Schematic created using CircuitLab

Best Answer

As OP has not clarified what 6V depletable source is to be used, this answer predicates a battery which has a nominal full charge voltage of 6 Volts, and is operable down to 3 Volts.

As discussed in comments, there are few if any options for an integrated buck-boost device in a 0.1 inch pin pitch DIP form factor. Further, with most manufacturers DIP is rapidly going out of production to be replaced by SMD, so it is inadvisable to use a DIP part for a new design, even if one finds such an option.

A parametric search for SEPIC / buck-boost ICs with the stated criteria, on a major vendor site such as DigiKey yields several options in SOIC packages. These are leaded packages with a 0.05 inch pin pitch, not extremely difficult to hand-solder. One DDPAK-5

Examples:

  • Linear Technology LT1572:

    1.25 Ampere monolithic switching regulator with inbuilt switching MOSFETs, in SOIC-16. Operates from 3 Volts to 30 Volts. Supports most switching topologies including SEPIC.

  • On Semiconductor CS5171:

    1.5 Ampere switching regulator with inbuilt switching MOSFETs, in SOIC-8. Operates from 2.7 Volts to 30 Volts. Similar to above, supports several topologies including SEPIC.

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