Switches: Analog MUX ICs & Load-Switch/eFuse ICs Selection Guide

A practical hub for two families of “switch” ICs: signal-path (analog switches & multiplexers) and power-path (load switches & eFuses). Structured for Know → Compare → Select/Do → Problem → Brand → Compliance, with calculators and BOM-oriented CTAs.

1) Definition & Use Cases

Analog switches / MUX ICs route small-signal paths (sensor → ADC, audio, test matrices, high-voltage measurement). Load switches / eFuses gate and protect power rails (soft-start, current limit, reverse blocking, OVP/UVLO, thermal).

Overview diagram showing signal-path MUX feeding an ADC and power-path load switch with eFuse protecting a downstream rail. — Fig. A — Signal-path vs power-path roles at a glance.

2) Types

Analog Switch / MUX

SPST/SPDT, 4:1 / 8:1 / 16:1, rail-to-rail, break-before-make, low R_ON, low leakage, low charge injection, audio/precision/HV variants.

Load Switch

High-side MOSFET with soft-start (dV/dt), low R_ON, enable logic, reverse blocking, quick-output-discharge (QOD), sequencing.

eFuse / Hot-Swap

Programmable current-limit, OVP/UVLO, short-circuit response, thermal foldback, fault reporting, ideal-diode ORing, surge robustness.

3) Selection — Signal Path (Analog Switch / MUX)

Core tradeoffs: R_ON & flatness, leakage, bandwidth/THD, charge injection, t_ON/t_OFF, logic levels and ESD. For ADC front-ends, ensure settling within the sampling window (R_SRC + R_ON with C_S/H).

Analog MUX into ADC sample-and-hold showing RC time constant from source resistance plus switch on-resistance into sampling capacitor. — Fig. B — MUX→ADC settling window and RC drivers.

Use Case	Key Specs	Quick Rules
Sensor→ADC MUX	Low R_ON/flatness, low charge injection, leakage < signal level, rail-to-rail	t_settle ≥ 7×(R_SRC+R_ON)·C_S/H; break-before-make
Audio switching	THD, bandwidth, click-pop control	Choose audio-grade switch; manage biasing
HV measurement	High off-isolation, leakage, HV rating	Prefer dedicated HV analog switches

4) Selection — Power Path (Load Switch / eFuse)

Size for inrush (C_load, dV/dt), current-limit window, R_ON loss, reverse blocking, and fault handling. Consider sequencing, QOD, telemetry, and thermal foldback for reliability.

Inrush current versus dV/dt with a load capacitor and a programmable soft-start ramp in an eFuse or load switch. — Fig. C — dV/dt programming tames inrush on rail start-up.

Rail	Design Inputs	Quick Rules
FPGA/SoC core	C_load, I_peak, sequencing, QOD	I_LIM ≥ 1.5× I_peak; add reverse blocking
USB/SSD	Hot-plug, surge/ESD, UVLO/OVP	Use eFuse with surge rating & reporting
Automotive 12 V	ISO 7637-2, load dump, reverse battery	AEC-Q100 eFuse + ideal diode/ORing

5) Calculators — Downloads

ADC-MUX Settling Mini-Worksheet (Excel)

Filename: adc-mux-settling-worksheet.xlsx

Fields: R_SRC, R_ON, C_S/H, t_sample, N-bit, V_FS, target-settling (ppm), recommended t_acq, max sampling rate.

Download (placeholder)

Inrush / Soft-Start Calculator (PDF)

Filename: inrush-softstart-calculator.pdf

Fields: V_IN, C_load, dV/dt, I_inrush=C·dV/dt, R_ON, I_LIM, P_diss, thermal rise estimate, pass/fail flags.

Download (placeholder)

6) Problems & Fixes

ADC code jump after MUX switch

Increase t_acq, buffer the source, choose lower R_ON/charge injection, ensure break-before-make.

Hot-plug brownout

Program dV/dt; check I_peak vs I_LIM; add QOD; verify reverse blocking & surge path.

Audio click/pop

Use audio-grade switch, manage bias, ramp enable, add small RC to tame steps.

7) Brand Matrix — TI / ST / NXP / Renesas / onsemi / Microchip / Melexis

Texas Instruments

Analog switches/MUX: TMUX, TS3A/TS5A, HD3SS (HS lines). Power: TPS229xx (load), TPS259x/TPS266x (eFuse/hot-swap, industrial/auto).

STMicroelectronics

Switch/MUX: STG/HC families. Power: STMPS / STEF series for load-switch & protection.

NXP

Switch/MUX: NX3L4051/CBT* families; interface-centric switch parts. (Power protection often via interface/USB power parts.)

Renesas (Intersil)

eFuse/USB power: ISL618x/ISL8xxx; analog switch coverage by selected parts.

onsemi

Protection/eFuse/Hot-swap: NCP38x/NCP36x/NIS502x lines for industrial/auto rails.

Microchip

Load switches/USB power: MIC20xx/MIC254xx; selected analog switch families.

Melexis

Automotive domain focus; switch/protection often integrated at subsystem level; consider as alternatives in vehicle power distribution.

8) Compliance & Application Standards

Interfaces: USB/HDMI hot-plug behavior, eye-diagram integrity, EMI; IEC 61000-4-2 (ESD), -4-5 (surge).
Safety: IEC 62368-1 creepage/clearance where applicable.
Automotive: ISO 7637-2 transients, ISO 16750 environmental; load dump, reverse battery, AEC-Q100.

Frequently Asked Questions

What is the difference between an analog switch and a multiplexer?

A switch connects/disconnects one path; a MUX selects one of many to a common node. For ADC front-ends, prefer rail-to-rail devices with low charge injection and break-before-make timing.

Load switch vs eFuse — when to use each?

Use load switches for simple on/off and soft-start; use eFuses when you need programmable current-limit, surge handling, OVP/UVLO and fault reporting or hot-swap behavior.

Why do ADC readings jump after channel switching?

Insufficient settling into the S/H cap or charge injection. Increase acquisition time, reduce R_ON, buffer the source, and ensure break-before-make.

How to size eFuse current-limit for motors or FPGAs?

Estimate I_peak and inrush; set I_LIM with margin (≈1.5×). Program dV/dt to tame inrush; verify thermal foldback and fault-response timing.

Do I need AEC-Q100 parts for in-vehicle rails?

For production vehicles, yes—seek AEC-Q100 grades and ISO 7637-2/load-dump robustness. For prototypes or infotainment off-critical rails, evaluate risk and protections carefully.

Resources & RFQ — Downloads & Request-for-Quote

Downloads (placeholders)

ADC-MUX Settling Mini-Worksheet (Excel)
Inrush / Soft-Start Calculator (PDF)
Switches Quick-Ref Cheatsheet (PDF) — Filename: switches-cheatsheet.pdf

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