# BQ25792 Charger

A **buck-boost battery charger** board built around the Texas Instruments **BQ25792**, a
switch-mode 1S to 4S charger with integrated USB-C input, I2C control, on-chip ADC and a fully
integrated power path. This page carries an **interactive 3D model** of the assembled board plus
schematic and layout views, so you can inspect the real design without opening Fusion.

Designed by **Adonis** in Autodesk Fusion 360 Electronics (Main project). The board integrates
**14 Adom machine pins** (`MP1` to `MP14`) so it presses into the Adom modular stack, mating with
machine contacts on adjacent boards.

## The 3D model above

The interactive viewer shows the fully-placed board: green soldermask, gold plating, the BQ25792
charger IC and power stage, passives, connectors, and the **Adom machine pins standing vertical**
around the board edges. Drag to orbit, scroll to zoom. Colors are the real Fusion materials,
preserved through the STEP to GLB pipeline.



## Exploded stackup view (current 3D model)

The 3D viewer above currently shows the board EXPLODED by layer (2 mm per slot) so you can see
every layer of the stackup in correct order, top to bottom:

components -> top silkscreen -> top soldermask -> top copper (layer 1) -> inner copper layer 2 ->
FR4 core -> inner copper layer 15 -> bottom copper (layer 16) -> bottom soldermask -> bottom silkscreen

The outer copper, masks, FR4 and components are the real exported 3D bodies, shifted apart. The
INNER copper layers (2, 15) and the silkscreens do not exist as 3D bodies in a Fusion export, so
they are the actual gerber layers rendered to copper/white images, registered to the board outline.
The assembled (non-exploded) model is `bq25792-charger-assembled.glb` in Files.

## Board stackup (exact physical fabrication stack)

Layer set from the EAGLE design rules: `layerSetup (1+2*15+16)` = 4 copper layers, `mtCopper` 0.035 mm
each. A 4-layer board is fabricated as **copper / prepreg / copper / core / copper / prepreg / copper** -
a thin core carries the two inner copper layers, then prepreg is bonded top and bottom with the outer
copper. The FR4 is NOT one slab: it is prepreg + core + prepreg. Dielectric split fitted to the
measured board (1.516 mm total dielectric): outer prepregs 0.200 each, core 1.046. Exact z, mm:

| # | Layer | z bottom | z top | thickness |
|---|---|---|---|---|
| 1 | Components (seated on top mask) | 1.582 | varies | per part |
| 2 | Top silkscreen | 1.582 | 1.582 | ink |
| 3 | Top soldermask | 1.516 | 1.582 | 0.066 |
| 4 | Copper L1 (top, traces) | 1.516 | 1.551 | 0.035 |
| 5 | Top prepreg (FR4) | 1.316 | 1.516 | 0.200 |
| 6 | Copper L2 (inner) | 1.281 | 1.316 | 0.035 |
| 7 | Core (FR4) | 0.235 | 1.281 | 1.046 |
| 8 | Copper L15 (inner) | 0.200 | 0.235 | 0.035 |
| 9 | Bottom prepreg (FR4) | 0.000 | 0.200 | 0.200 |
| 10 | Copper L16 (bottom) | -0.035 | 0.000 | 0.035 |
| 11 | Bottom soldermask | -0.065 | 0.000 | 0.065 |
| 12 | Bottom silkscreen | -0.065 | -0.065 | ink |

Copper L1 and L16 are the real exported 3D bodies (routing as geometry). Inner copper L2 and L15 are
the real gerber layers (`copper_l2.G1`, `copper_l3.G2`) - Fusion does not export inner layers as
bodies. Outer prepreg/core split is symmetric to the measured board; the exact fab dielectric ratio
comes from `mtIsolate` when the fab sets it explicitly.

### Exploded view placement (physical, 6.000 mm per slot, real thicknesses)

Each layer is its own slab at its EXACT thickness, separated by 6 mm. The FR4 appears as its three
real sublayers (top prepreg, core, bottom prepreg) with the four copper layers between them:

| Element | slot | z-center in exploded model (mm) | thickness (mm) |
|---|---|---|---|
| Components | +7.5 | 45 (pins hang 7.8 below seats; clears silk at 30) | per part |
| Top silkscreen | +5 | 30 | ink |
| Top soldermask | +4 | 24 | 0.066 |
| Copper L1 (top) | +3 | 18 | 0.035 |
| Top prepreg (FR4) | +2 | 12 | 0.200 |
| Copper L2 (inner) | +1 | 6 | 0.035 |
| Core (FR4) | 0 | 0 | 1.046 |
| Copper L15 (inner) | -1 | -6 | 0.035 |
| Bottom prepreg (FR4) | -2 | -12 | 0.200 |
| Copper L16 (bottom) | -3 | -18 | 0.035 |
| Bottom soldermask | -4 | -24 | 0.065 |
| Bottom silkscreen | -5 | -30 | ink |

## What the BQ25792 does

| Feature | Detail |
|---|---|
| Type | I2C-controlled buck-boost battery charger |
| Cell count | 1 to 4 cells in series (1S to 4S) |
| Charge current | Up to 5 A |
| Input | USB-C and generic DC, wide input range with input current optimizer |
| Power path | Integrated, so the system runs while charging |
| Telemetry | On-chip 16-bit ADC (voltage, current, temperature) |
| Extras | Dual-input selection, MPPT for solar, integrated FETs |

## Board (Fusion, v222)

| Property | Value |
|---|---|
| Outline (FR4) | 50.40 x 26.40 mm |
| Components | 109 (108 top, 1 bottom) |
| Signals | 50 nets (3 airwires still to route) |
| Pads | 304 |
| Vias | 88 |
| Holes | 176 |
| Adom machine pins | 14 (MP1 to MP14) |

## Adom machine pins

The board uses the Adom **press-fit machine pin** system for board-to-board stacking. Each pin
presses into a plated through-hole and mates with a machine contact on a stacked board. See the
pin components:

- [Machine Pin Medium Standard](https://wiki.adom.inc/adom/machinepinmediumstandard)
- [Adom Machine Pins, Fusion Library](https://wiki.adom.inc/adom/adom-machine-pins-fusion-lbr)

## Files (everything exportable is here - this page is for sharing)

| File | What |
|---|---|
| `bq25792-charger.f3d` | Fusion 360 archive (native) |
| `bq25792-charger.step` | STEP 3D (full board) |
| `bq25792-charger.usdz` | USDZ 3D (PBR) |
| `bq25792-charger.brd` / `.sch` | EAGLE board + schematic source |
| `bq25792-charger.fbrd` / `.fsch` | Fusion-native board + schematic |
| `bq25792-charger-gerbers.zip` | Fabrication gerbers + drill (13 files) |
| `bq25792-charger-bom.csv` | Bill of materials |
| `bq25792-charger-cpl.csv` | Pick-and-place (component placement) |
| `bq25792-charger-exploded.glb` | Exploded stackup 3D (current viewer model) |
| `bq25792-charger-assembled.glb` | Assembled 3D (real copper traces, translucent mask) |
| `bq25792-3d-iso.png` / `-3d-top.png` / `bq25792-schematic.png` | Renders |

## Provenance

Source of truth is the live Fusion 360 design (Main project, document version 222). This page is a
snapshot for browsing and reuse. To edit the board, open the project in Fusion.