Timers & RTCs
Timer ICs and real-time clocks: supply behavior, decoupling, and timing accuracy.
Written and verified by John Merton · verified 2026-07-10
Timer ICs generate precise time intervals with an RC network or an external clock. The NE555 is the category's archetype — arguably the most-produced IC in history — and its page covers the three classic modes (monostable, astable, bistable) plus the CMOS variants (LMC555, TLC555) that fix the original bipolar part's supply glitch and output drive quirks.
How to choose
The axes below are the criteria you actually weigh when selecting a part in this category.
- Bipolar vs CMOS timer variants
- The original NE555 draws a supply glitch on every output transition. CMOS variants like the LMC555 and TLC555 eliminate it but have lower output drive. Pick based on your supply noise budget.
- See:NE555
- Timing accuracy: RC tolerance and capacitor type
- An RC timer is only as accurate as its components. Electrolytic capacitors drift with age and temperature; film or NP0/C0G ceramics hold timing over temperature and years of operation.
- See:NE555
- Supply voltage range and output drive
- The NE555 runs from 4.5–16 V and can source/sink 200 mA. CMOS variants run from 2–15 V but drive less current. Match the output current to what you are actually switching.
- See:NE555
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Parts in this guide verified against manufacturer datasheets; latest 2026-07-10.
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