TI AUTOMOTIVE · power
Automotive power selection: LDO, DC/DC, PMIC and supervisor roles
Select TI automotive power devices by input envelope, load rails, thermal budget and sequencing. Separate converters, controllers, PMICs and supervisors without combining unrelated maximum ratings.
Sources reviewed 2026-11-06 · NuAxi technical editorial · source facts and engineering interpretation distinguished
Key answer
Draw the power tree first. An LDO serves rails whose dissipation is acceptable; DC/DC performs efficient conversion; a PMIC coordinates multiple rails and sequencing; a supervisor detects faults and resets the load. These roles often coexist.
Choose a role, not a part-number prefix
The TPS prefix spans very different functions: TPS7B81 is an LDO, TPS55288 a buck-boost converter, TPS6594 a multirail PMIC and TPS3840 a supervisor. The category defines the system role, but the device still needs input, load and fault-policy review.
Scroll wide tables horizontally; column headers remain visible within the table.
| Role / example | Responsibility | Do not infer |
|---|---|---|
| LDO · TPS7B81-Q1 | Linear regulation with low light-load IQ | A 40V limit does not support a nominal 48V input |
| Buck · LMR33630-Q1 | Synchronous step-down with integrated switches | Not boost; 3A remains thermally constrained |
| Controller · LM5143-Q1 | Controls external stages for dual or multiphase rails | Not an integrated high-current power module |
| PMIC · TPS6594-Q1 / LP8764-Q1 | Multirail power, configuration and sequencing | Similar use does not imply identical NVM, pins or LDO count |
| Supervisor · TPS3840-Q1 | Undervoltage detection, reset and delay | Neither a regulator nor a watchdog |
Separate quiescent current from load dissipation
TPS7B81-Q1 has a typical light-load IQ of 2.7µA, but that is not the rail's total power loss. As an arithmetic example, 12V to3.3V at100mA dissipates approximately (12−3.3)×0.1=0.87W before quiescent loss. This is not a recommended operating point.
Estimate junction temperature from the actual PCB, ambient temperature and heat path. One datasheet test-board thermal metric is not universal. A preregulator plus LDO may help when loss is excessive, but noise, dropout and startup timing still need validation.
Converter versus controller: current evidence differs
LMR33630-Q1 integrates power switches and lists 3A output capability; LM5143-Q1 relies on external MOSFETs, inductors, sensing and cooling. A controller selector-table entry such as40A is not a board-level guarantee at arbitrary conditions.
TPS55288-Q1's16A figure concerns inductor/switch capability; load current also depends on boost ratio, efficiency and limit settings. Record minimum input, maximum output power, peak current and sustained temperature rise instead of ranking headline amperes.
Steady rails do not prove startup or fault recovery
Multicore processors require rail order, dependencies, reset release and fault-response checks. TPS6594-Q1 and LP8764-Q1 provide configuration and monitoring resources, but the actual NVM and safety material must match the processor platform.
TPS3840-Q1 handles undervoltage/manual reset, not software liveness. Use a watchdog or a supervisor with that function, and review its window and startup behavior.
- List each rail's input envelope, output tolerance, sustained/peak current and allowed noise.
- Calculate loss/temperature and verify frequency, output, threshold and temperature definitions by exact OPN.
- Test startup, shutdown, undervoltage recovery, communication failure and reset polarity, not just steady load.
- Record AEC-Q100, functional-safety documents, EMC tests and system safety targets separately.
Frequently asked questions
Can a PMIC remove the preregulator?
It depends on input conditions. TPS6594-Q1/LP8764-Q1 are low-voltage-input PMICs, not direct12V/48V front ends; bring the input within their operating range.
Does lower IQ always mean lower system power?
No. Light-load residence time, voltage-drop loss, conversion efficiency, external resistors and wake policy determine system energy. Compare the actual duty cycle.
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.