Video summary

The Great Search: 3.3V Buck-Boost Converter #TheGreatSearch #digikey #Adafruit @DigiKey @adafruit

Main summary

Key takeaways

Product Review

Product Being Reviewed

A 3.3V buck-boost voltage regulator intended to run from either:

  • 2× AA batteries, or
  • USB 5V

The goal is powering electronics such as an ESP32, especially when Wi‑Fi/audio loads require around ~500mA.

What It Does / Main Application

The regulator:

  • Accepts input from either source:
    • ~1.8–3.0V from 2× AA batteries (down to ~0.9V per cell)
    • ~5V from USB (noted as up to ~5.5V max)
  • Produces a fixed ~3.3V output using a buck-boost topology, allowing operation whether the input voltage is above or below the target output.

Key Features Emphasized (Selection Criteria)

The reviewer is looking for an “all-in-one” regulator that meets these preferences:

  • Synchronous rectification
    • No external catch diode
    • Better efficiency and “true power disconnection” is mentioned
  • Single-output, positive-only regulation
    • No inversion
  • A regulated part
    • Not a controller that requires extra external transistor/diode circuitry
  • Input capability:
    • Minimum around ~1.8V
    • Maximum around ~5.5V
  • Package preference:
    • Avoids BGA packages

They also emphasize:

  • Low quiescent current, because the converter will be mostly always on even when the audio load is inactive.

Models / Components Mentioned and Comparisons

TPS61023 (previous/reference approach)

Used as a reference point. The described approach:

  1. Boost the battery input up to ~3.8V
  2. Use an OR-diode power selector between battery and USB
  3. Generate clean 3.3V with an LDO

The reviewer calls this approach somewhat “un-kosher,” implying it is more complex than necessary.

Buck-boost vs separate boost/buck (general discussion)

  • If input is above the target output: buck-leaning designs can make sense
  • If input is below the target output: boosting becomes necessary The reviewer discusses this as general reasoning for topology choice.

DigiKey filtering results

  • Filtered to low-voltage buck-boost regulators in stock
  • Then narrowed to fixed 3.3V output
  • Mention of sorting by price (around ~$1), leaving roughly ~10 options after further narrowing

TPS63xxx family (context)

  • Buck-boost line referenced
  • Example mentioned: TPS63060
    • 5V buck-boost from 3–12V
    • roughly ~500mA–1A
    • used as evidence of familiarity with the family

Other candidates (not selected)

  • Mentions search set includes parts from Richtek and Renesas, but none were selected
  • TPS61030 is called out as a strong candidate due to price/in-stock availability and matching specs

Final Recommendation / Pick

Selected part: TPS61030

Why it’s chosen:

  • Price: ~$1 (in the stated quantity)
  • Availability: “lots in stock”
  • Key quoted specifications:
    • Input range: 1.8V to 5.5V
    • Output current: up to ~1.2A output
    • Capable of stepping down from ~2.4V to ~500mA
    • Can handle around ~500mA from ~1.8V (per mentioned datasheet-style figures)

Reviewer emphasis points:

  • Low quiescent current
  • Simple/easy schematic
  • No diode needed because it is synchronous
  • No feedback divider needed because output is fixed at 3.3V

Load / Current Reasoning (Engineering Considerations)

The target application uses about ~500mA output, such as:

  • driving a speaker
  • running an ESP32 in Wi‑Fi mode

Important clarification made by the reviewer:

  • ~500mA output is not the same as switch current on a buck-boost.
  • At the low end of input (~1.8V), the required switch peak current may be roughly “doubling.”
    • Hence their estimate that you may need ~1A+ switch current.

They warn that options rated near 800–900mA switch current may be borderline, especially:

  • as batteries age/droop
  • with inefficiency headroom added (around ~20–25%)

Pros / Cons Mentioned

Pros

  • Works from both low-voltage AA batteries and USB 5V
  • Fixed 3.3V output (simpler than adjustable regulators)
  • Synchronous rectification → better efficiency and simpler circuitry (no external diode)
  • Low quiescent current suitable for “always on” with burst activity
  • Simple schematic (few external components)
  • Strong availability and cost: ~$1 and “lots in stock”
  • Reviewer has prior familiarity/trust in the TI family

Cons / Limitations (Implied)

  • Must confirm the part can supply sufficient switch current at low battery voltage
  • Borderline switch-current ratings may fail under real-world conditions without sufficient headroom

Verdict / Overall Recommendation

The conclusion is that a TI TPS61030 best matches the requirements:

  • A synchronous buck-boost regulator
  • Produces fixed 3.3V from ~1.8V AA batteries or ~5V USB
  • Offers low quiescent current, simple design, and sufficient current capability for a ~500mA-class load
  • Provided that current/switch-current headroom is properly accounted for

Core assumption: proper current budgeting (including ~20–25% inefficiency headroom) is required for reliable performance.

Unique Points Mentioned (Complete List)

  • Buck-boost used to support either low (battery) or high (USB) input while keeping a 3.3V output
  • Prior approach: TPS61023
    • boost battery to ~3.8V
    • OR-diode selector
    • LDO to 3.3V
    • considered more complex than necessary
  • Search conducted on DigiKey with “Great Search”
  • Criteria: filter for a regulator, not a controller
  • Preference for single fixed positive output (no inversion)
  • Preference for synchronous rectification (efficiency + avoids external diode)
  • Input constraints:
    • minimum ~1.8V (from 2× AA down to ~0.9V/cell)
    • maximum ~5.5V
  • Excludes BGA packages
  • Filters to fixed 3.3V, then evaluates the reduced option set
  • Price target noted around ~$1
  • Current reasoning rule-of-thumb:
    • load ≈ ~500mA output
    • need enough switch current peak at low input (≈ double estimate)
    • recommends ~20–25% headroom
  • Final selection: TPS61030
    • 1.8–5.5V input, up to ~1.2A output
    • supports ~500mA from ~1.8V
    • low quiescent current
    • simple external design: no diode, no feedback divider (fixed output)
    • good availability (“lots in stock”)
  • Mention of TPS63xxx family, including example TPS63060, as prior reference/familiarity

Speaker Views / Contributions

  • Main reviewer speaker:
    • drives the overall design intent
    • searches DigiKey using constraints
    • explains electrical reasoning (especially switch current vs output current)
    • selects TPS61030 as the best fit

Original video