TI AUTOMOTIVE · power
12V/48V automotive power: operating input, transients and absolute maximum ratings
Use TI LDO, boost and wide-input buck examples to distinguish nominal bus voltage from pin stress. Check cold crank, load dump, reverse connection and thermals without treating survival limits as operating points.
Sources reviewed 2026-11-06 · NuAxi technical editorial · source facts and engineering interpretation distinguished
Key answer
12V or48V describes a nominal system bus, not the full voltage envelope at a device pin. Establish steady-state and transient conditions, then choose protection and conversion. Absolute maximum ratings concern damage avoidance, not guaranteed regulation.
Define four input states first
This is an engineering review framework, not a universal OEM pulse specification. Obtain amplitudes, durations, source impedances and repetitions from the applicable project requirements. A TVS nominal clamp value is not a fixed pin voltage at arbitrary energy.
Scroll wide tables horizontally; column headers remain visible within the table.
| State | Check | Common mistake |
|---|---|---|
| Steady supply | Recommended range, regulation and thermal budget | Checking nominal12V/48V only |
| Cold-crank dip | Start/run thresholds, UVLO, dropout and hold-up | Equating minimum run voltage with startup |
| Positive transient | Pin peak/duration, clamping and survival conditions | Treating transient survival as continuous VIN |
| Reverse/negative stress | Negative pin limits, return paths and protection | Assuming Q1 implies reverse protection |
Separate three kinds of voltage figures
TPS7B69-Q1 specifies4–40V operating input; its absolute-maximum footnote limits45V transients to200ms. This is a stress-survival limit, not a regulation guarantee. It is not a direct LDO for a nominal48V bus. LM5143-Q1's3.5–65V range is a candidate for protected48V architectures, but project transients still require analysis and testing.
TPS55288-Q1 has a36V maximum input range; an automotive-power category does not permit direct48V connection. Navigation categories are not electrical ratings. Keep continuous/transient, start/run and TA/TJ conditions attached to every number.
Startup and continued operation are different
LM5155-Q1 can continue boost operation from1.5V input only when BIAS is at least3.5V; tying BIAS to VCC has a separate range. The system may need auxiliary bias or a different startup path. A1.5V label alone does not guarantee cold start.
Test minimum input, peak load, input capacitance, startup slope and reset thresholds together. Continued communication during a dip does not prove processor sequencing or analog accuracy on every rail.
Tie protection, conversion and validation together
Record worst-case conditions at device pins, not just the connector. The following NuAxi checklist is engineering guidance, not a claim that TI has qualified your ECU.
- Steady limits and pulse amplitude/duration/source impedance have project evidence.
- Post-protection/pre-IC pin voltages stay within limits including tolerance and parasitics.
- Review recommended conditions, absolute maximums, transient survival and power-device SOA separately.
- Validate startup, reset, current limiting and recovery at hot/cold temperatures and peak loads.
- Keep AEC grade separate from junction temperature, with datasheet revision and test conditions.
Frequently asked questions
Can a TVS make a36V-input device run on48V?
A transient clamp is not a solution for continuous input above the operating range. Use a suitable preregulator or rated device, with protection-energy and steady-loss analysis.
Does AEC-Q100 Grade1 guarantee all automotive pulse tests?
No. Device reliability qualification and ECU transient/EMC/input testing are distinct tasks. Validate project conditions and the protection network.
Related parts and complete OPNs
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NuAxi is independent of TI. This guide organizes official evidence and engineering checks; it is not substitution approval, system certification, procurement assurance or completed design validation. Review the exact OPN, datasheet revision and project requirements.