App note: TPS6122x low input voltage, 0.7V boost converter with 5.5μA quiescent current


An application note from TI, TPS6122x low input voltage, 0.7V boost converter with 5.5μA quiescent current (PDF!):

The TPS6122x family devices provide a power-supply solution for products powered by either a single-cell, two-cell, or three-cell alkaline, NiCd or NiMH, or one-cell Li-Ion or Li-polymer battery. Possible output currents depend on the input-to-output voltage ratio. The boost converter is based on a hysteretic controller topology using synchronous rectification to obtain maximum efficiency at minimal quiescent currents. The output voltage of the adjustable version can be programmed by an external resistor divider, or is set internally to a fixed output voltage. The converter can be switched off by a featured enable pin. While being switched off, battery drain is minimized. The device is offered in a 6-pin SC-70 package (DCK) measuring 2 mm x 2 mm to enable small circuit layout size.

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  1. TI makes some great stuff, but knowing this part, I would buy some MCP1640 or equivalent instead.
    Notice they did not have a feature line item on its current delivery ability. :-p
    The usual efficiency graph? In the PDF I have, they put it on page 6. Ahem.
    It runs out of gas at 50mA. Well, enough for a 2x5mm LED white torch, but still…
    Given a selection of parts for hobby projects, I would still prefer a bit better current capability.
    The problem (for hobbyists) with this class of ICs (low-Vin-start switchers) is their FET, the resistance is pretty high given the design targets, none I saw will give you say 500mA load capability, although say a Li-ion is capable of high loads. So hobbyists should watch out lest they end up with brownouts when switching on heavier loads in their projects.

  2. These parts have been around for at least 5 years and are well characterized. There are nice low power and shutdown features for sipping on the battery when in shutdown. Efficiency isn’t bad in the sweet spot, which is pretty broad. A big plus for some is that TI provides a working PSpice model to download. On the downside: You are lucky to push output current to 80mA, plus keep a close eye on your output ripple. This is a fun little part to toss into a simple one cell one led flash light project as you pull it from the back of an envelope, through SPICE sim, and onto a breadboard.

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