Design Log DEC 005 tps25980 efuse replaces tps259474l - thepinkmile/Enigma-NG GitHub Wiki
DEC-005 - TPS25980 eFuse Replaces TPS259474L
- Status: Decided
- Date: 2025
- Category: Electrical
- Area: Power Module eFuse (U1)
Decision
The input eFuse uses a TPS25980 (7A ILIM, silicon-fixed 16.9V OVLO) rather than the originally considered TPS259474L (5.5A ILIM).
Rationale
- TPS259474L 5.5A limit is insufficient for worst-case USB-C 15V path at 75W: 75W / 15V = 5.0A + 10% derating = 5.5A - already at the device limit with no headroom.
- TPS25980 (TPS259804ONRGER) provides 7A ILIM (programmed via R3 = 210 Ω) and silicon-fixed 16.9V OVLO, which neatly caps the battery charge voltage window.
OVLO Constraint
- eFuse OVLO is 16.9V silicon-fixed (TPS259804ONRGER - no external programming resistor).
- BMS must be configured for 4.1V/cell maximum charge (16.4V for 4S) to maintain a ≥0.5V margin.
- BMS configurations using 4.2V/cell (16.8V) are not compatible with this eFuse and must not be used.
⚠️ Variant Lock - Do NOT change this MPN
The TPS25980 family uses a digit after TPS25980 to select the OVLO behaviour:
| Variant | OVLO | Status |
|---|---|---|
| TPS259804ONRGER | 16.9V silicon-fixed | ✔ CORRECT - use this |
| TPS259807 | No OVLO feature | ❌ WRONG - do not use |
| TPS259803 | No OVLO feature | ❌ WRONG - do not use |
This variant has been erroneously swapped to TPS259807 in previous review rounds.
The 04 digit must not be changed without explicit documented justification.