Load Switch
A load-switch IC controls power to a downstream circuit. Integrated drive circuitry operates its switching transistor, often with controlled turn-on to limit inrush. Quick output discharge, current limiting, reverse-current blocking and diagnostics are selection features, not guarantees carried by the family name.
An enable or control input commands the internal power path. Where supported, a controlled output rise slows the charging of downstream capacitance and reduces inrush. Some parts provide adjustable timing, output discharge or fault protection; their implementation and conditions come from the exact data sheet. A load switch does not inherently regulate the output to a new voltage.
In plain terms
Think of a controllable doorway for electrical power. Some doorways open gently, some can detect an overload, and some drain the room's stored charge when closed. You must check which extras your particular switch actually has.
Why designers use it
- Turn a subsystem's power rail on or off.
- Manage startup inrush with a suitable controlled-rise device.
- Sequence rails or select additional fault protection when the chosen IC provides it.
Best for
- Subsystem power gating
- Controlled rail startup
- Compatible power sequencing
Key specifications
- Power path: Voltage, load current and on-resistance (Check thermal and startup conditions as well as steady operation.)
- Control: Enable levels and rise-time behavior (Timing may be fixed or adjustable, depending on the part.)
- Optional functions: Discharge, reverse blocking and fault protection (Confirm both feature presence and the conditions in which it operates.)
When not to use it
- When the required protection is absent or works only in operating states unsuitable for the application.
- When input voltage, current, thermal loss or startup conditions exceed the chosen device's limits.
Common mistakes
- Assuming every load switch blocks reverse current or discharges its output.
- Choosing by continuous current alone while ignoring inrush and thermal behavior.
- Expecting a load switch to behave like a voltage regulator.
- Ignoring the specific conditions under which a protection feature operates.
Where you will find it
- TI's portfolio page lists TPS22996 as a dual-channel device with adjustable rise time and TPS2001E as a USB power switch with output discharge and reverse blocking. These are named feature examples, not universal load-switch behavior.
- TI's TIDA-01584 reference design demonstrates power sequencing with load switches and independently adjustable rail timing. It is a published design example, not a claim about the hidden components inside a commercial computer.
A short history
Integrated load switches combine a controlled power path with device-specific management functions. TI's overview separates power sequencing, power loss and optional protection use cases. This guide uses those documented functions rather than attributing an unsupported origin date or a specific phone's internal power tree.
Good to know
- Controlled rise time and current limiting are related to startup behavior but are not identical features.
- Low on-resistance reduces the switch's conduction loss; it does not remove the need to check temperature rise.