2 layers75 × 106.5 mm
2 layers15 × 18 mm
Inverting buck boost
flaviut/5v-inverting-buckDesign for an inverting 5V buck-boost regulator based on the MT2499A, with performance data
- Size
- 15 × 18 mm
- Copper layers
- 2
- Thickness
- 0.57 mm
- Parts
- 12
- Nets
- 8
- Pads
- 43
- Tracks, vias
- 41, 31
- Pours
- 6
- Routed
- Yes
- KiCad
- KiCad 6 (file 20211014)
- Created
- 6 Feb 2023
- Updated
- 6 Feb 2023
Overview
Inverting buck boost is an open-source printed circuit board by flaviut, from the flaviut/5v-inverting-buck repository on GitHub. It is a 2-layer board of 15 × 18 mm with 12 parts on 8 nets, routed with 41 tracks and 31 vias.
It is built around the MT2499A. Its parts include 7 capacitors, 2 resistors, 1 IC, 1 connector and 1 inductor. It belongs with the power boards of this library.
Main components
1README
README.mdInverting buck-boost controller
Using the documentation in TI's SLVA458B, "Creating an Inverting Power Supply Using a Synchronous Step-Down Regulator", I've designed an inverting buck-boost regulator using the super-cheap Aerosemi MT2499A, and characterized its performance somewhat.
Testing
There's a massive amount of 7kHz ripple, up to 500mV before stopping testing at 300mA.
This seems to be related to very poor regulator stability. Placing 33pF in C5 improves ripple to 30mV between 0-220mA out, but the ripple is back to 500mV at 230mA.
| Cff | Imax |
|---|---|
| 32pF | 225mA |
| 54pF | 285mA |
Linear interpolation indicates 133pF would be needed for stability at 500mA, but I'm not sure if linear interpolation is valid here.
I also suspect that it is not possible to create a perfectly compensated regulator here, since the MT2499A is internally compensated, and the procedure that SLVA458B describes to compensate the regulator is just not possible.
Parts
12| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 22u | Capacitor_SMD:C_1210_3225Metric | C1, C2, C7, C8 |
| 2 | 100n | Capacitor_SMD:C_0603_1608Metric | C3, C4 |
| 1 | 200k | Resistor_SMD:R_0603_1608Metric | R1 |
| 1 | 47k | Resistor_SMD:R_0603_1608Metric | R2 |
| 1 | 47u | Inductor_SMD:L_Taiyo-Yuden_NR-50xx | L1 |
| 1 | Conn_01x03 | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical | J1 |
| 1 | DNP | Capacitor_SMD:C_0603_1608Metric | C5 |
| 1 | MT2499A | Package_SO:SOIC-8-1EP_3.9x4.9mm_P1.27mm_EP2.62x3.51mm_ThermalVias | U1 |
Questions
How big is the Inverting buck boost PCB?
It measures 15 × 18 mm and has 2 copper layers, 0.57 mm thick.
What parts does the Inverting buck boost use?
12 parts, built around the MT2499A. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Inverting buck boost KiCad files?
From the flaviut/5v-inverting-buck repository on GitHub, at the commit this page was made from: the board is inverting-buck-boost.kicad_pcb and its schematic inverting-buck-boost.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Inverting buck boost design in my own project?
Its repository states no licence, so its author keeps all rights: ask flaviut before reusing the design.
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