Answer: NE555P is TI’s bipolar 555 timer in an 8-pin PDIP, rated 0 to 70 °C and 4.5 to 16 V (Active, tube of 50, marking NE555P). Pinout: 1 GND, 2 TRIG, 3 OUT, 4 RESET, 5 CONT, 6 THRES, 7 DISCH, 8 VCC. Monostable pulse ≈ 1.1 × RA × C; astable tH ≈ 0.693 × (RA + RB) × C, tL ≈ 0.693 × RB × C. (TI SLFS022K pp.3, 4, 11, 12, 21.)
Key specifications
| Parameter | Value | Condition | Source |
|---|---|---|---|
| Supply voltage VCC | 4.5 to 16 V (recommended); 18 V absolute max | NE555 | p.4 §5.1, §5.3 |
| Operating temperature TA | 0 to 70 °C | NE555 (SA555: −40 to 85 °C) | p.4 §5.3; Addendum p.21 |
| Output current IO | ±200 mA recommended; ±225 mA absolute max | — | p.4 §5.1, §5.3 |
| THRES voltage level | 8.8 / 10 / 11.2 V (VCC 15 V); 2.4 / 3.3 / 4.2 V (VCC 5 V) | TA = 25 °C | p.5 §5.5 |
| TRIG voltage level | 4.5 / 5 / 5.6 V (VCC 15 V); 1.1 / 1.67 / 2.2 V (VCC 5 V) | TA = 25 °C | p.5 §5.5 |
| THRES current | 30 typ / 250 max nA | Sets max RA + RB ≈ 3.4 MΩ at 5 V, ≈ 10 MΩ at 15 V | p.5 §5.5, p.6 note 1 |
| RESET voltage level / current at 0 V | 0.3 / 0.7 / 1 V; −0.4 typ / −1.5 max mA | — | p.5 §5.5 |
| Low-level output voltage | 0.1/0.25 V @10 mA; 0.4/0.75 V @50 mA; 2/2.5 V @100 mA (VCC 15 V) | typ / max | p.6 §5.5 |
| High-level output voltage | 12.75 min / 13.3 typ V (VCC 15 V); 2.75 min / 3.3 typ V (VCC 5 V) | IOH = −100 mA | p.6 §5.5 |
| Supply current, no load | 10 typ / 15 max mA (out low, 15 V); 3 / 6 mA (out low, 5 V) | — | p.6 §5.5 |
| Timing drift | 50 ppm/°C typ (monostable), 150 ppm/°C (astable); 0.1 / 0.5 %/V supply sensitivity (monostable) | Not production tested | p.7 §5.6 |
| Output rise / fall time | 100 typ / 300 max ns | CL = 15 pF, 25 °C | p.7 §5.6 |
| Thermal resistance RθJA | 98.5 °C/W (P, PDIP-8) | — | p.5 §5.4 |
| ESD | HBM ±500 V; CDM ±1500 V | — | p.4 §5.2 |
Pinout (PDIP-8, top view)
| Pin | Name | Function (TI Table 4-1) |
|---|---|---|
| 1 | GND | Ground |
| 2 | TRIG | Start of timing: TRIG < ½ CONT sets the output high and the discharge open |
| 3 | OUT | Timer output |
| 4 | RESET | Active-low reset: forces the output and discharge low |
| 5 | CONT | Comparator threshold, nominally 2/3 VCC; bypass capacitor connection |
| 6 | THRES | End of timing: THRES > CONT sets the output and discharge low |
| 7 | DISCH | Open-collector discharge for the timing capacitor |
| 8 | VCC | Supply, 4.5–16 V |
(p.3.) Priority, per the note to Figure 6-1 (p.10): RESET overrides TRIG, which overrides THRES.
Ordering
| Orderable | Package | Status | Pack | Temperature | Marking |
|---|---|---|---|---|---|
| NE555P (also NE555P.A, NE555PE4) | PDIP (P), 8 pins | Active | Tube, 50 | 0 to 70 °C | NE555P |
(Addendum p.21.) The SO (PS) and TSSOP (PWR) versions are marked N555. NE555PW (TSSOP, tube) is listed as Obsolete.
Timing formulas and worked examples
- Monostable (Figure 6-2, p.11): tw ≈ 1.1 × RA × C. With RA = 100 kΩ and C = 10 µF, tw ≈ 1.1 s. The minimum pulse is about 10 µs, and TRIG must return high at least 10 µs before the interval ends.
- Astable (Figure 6-5, Equations 1–3, p.12): tH ≈ 0.693 × (RA + RB) × C, tL ≈ 0.693 × RB × C. TI’s own example (RA 5 kΩ, RB 3 kΩ, C 0.15 µF) gives tH 0.83 ms and tL 0.31 ms, so T ≈ 1.14 ms (about 875 Hz) with the output high 73 % of the time.
- The basic astable circuit therefore always runs above 50 % high time, because C charges through RA + RB but discharges through RB only (p.12).
- TI recommends 100 kHz or below in astable mode and points to the CMOS TLC555 for higher frequencies (p.12).
- The THRES input current limits RA + RB to about 3.4 MΩ at 5 V and about 10 MΩ at 15 V (p.6, note 1).
Output stage at 5 V vs 15 V
The output is a bipolar totem pole, and its drop grows with current:
- At VCC 15 V and 100 mA sink, the low level is 2 V typ / 2.5 V max (p.6).
- At VCC 5 V and 100 mA source, the high level is only 2.75 V min (p.6).
A 5 V NE555P driving a relay or LED string at 100 mA will not swing rail to rail; check the load against these numbers.
Supply and decoupling
- Fit a 0.1 µF ceramic from VCC to GND (§7.3, p.18).
- TI’s astable figure also shows 0.01 µF from CONT to GND (Figure 6-5, Note A, p.12).
- Supply current is 10 mA typ / 15 mA max at 15 V with the output low and no load (p.6). That is 150–225 mW before any load current.
Pitfalls specific to the NE555P
- Running from 3.3 V. VCC minimum is 4.5 V (p.4).
- Leaving RESET floating. TI says to tie RESET to VCC when unused to prevent false triggering (p.11).
- Expecting a 50 % square wave from the basic astable. The high time is always longer than the low time (Equations 1–2, p.12).
- Using −40 °C outdoors. The NE555 is 0 to 70 °C only; the SA555 covers −40 to 85 °C (p.4).
- Huge timing resistors. Above about 3.4 MΩ (at 5 V) the THRES current dominates (p.6).
- Rough handling. HBM ESD is only ±500 V (p.4).
Related pages
- Power calculator for the supply-current and output-stage dissipation
- AMS1117-5.0 as a 5 V supply rail for the NE555P
- LM317 in TO-220 for an adjustable 5–15 V rail
FAQ
- What is the NE555P pinout? 1 GND, 2 TRIG, 3 OUT, 4 RESET, 5 CONT, 6 THRES, 7 DISCH, 8 VCC (TI SLFS022K p.3).
- What voltage does the NE555P need? 4.5 to 16 V recommended, 18 V absolute maximum. It does not run from 3.3 V.
- What is the NE555P temperature range? 0 to 70 °C. For −40 °C use an SA555 (−40 to 85 °C).
- How do I calculate a 555 pulse width? Monostable: tw ≈ 1.1 × RA × C, e.g. 100 kΩ and 10 µF give about 1.1 s.
- Why is my 555 astable duty cycle above 50 %? C charges through RA + RB but discharges through RB only, so tH > tL in the basic circuit.
- What should I do with the RESET pin? Tie it to VCC when unused; a floating RESET can cause false triggering.
Related (internal links)
Sources (retrieved 2026-10-26)
- Texas Instruments, xx555 Precision Timers (NA555, NE555, SA555, SE555), SLFS022K (revised March 2026): https://www.ti.com/lit/ds/symlink/ne555.pdf
Disclaimer
Values are copied from TI SLFS022K (revised March 2026) and its Package Option Addendum, read on 26 Oct 2026. Timing-drift figures are characterised, not production tested (p.7). Other makers’ NE555 parts have their own datasheets.
Reviewed by: Jasper · Updated: 2026-10-26