BETARecommended supply4.5–16 V
Dual bipolar timer
NE556 Specifications
Review NE556 electrical specifications, operating conditions and package details.
Package view
Key specifications
Choose a separate RC network for each timer. Reset can stop either channel while the other continues.
Independent timers2 Separate timing networks
Ambient range0–70 °C · NE grade
Physical contacts14 PDIP / SOIC
Package details
NE556N · PDIP-14
| Property | Details |
|---|---|
| Manufacturer | Texas Instruments |
| Part number | NE556N |
| Package | PDIP-14 |
| Connections | 14 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | dip |
| Thermal reference | Board and package dependent; see manufacturer data |
Operating conditions
NE556 grade
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Supply | 4.5–16 V | Recommended operating range |
| Ambient temperature | 0 to +70°C | NE556N / NE556DR |
| Output loading | Up to ±200 mA specified | Check output drop and package dissipation; not a promise of rail-to-rail swing |
| Example supply | 5 V | Common to both channels |
| Local decoupling | 100 nF | Directly across pins 14 and 7 |
No specifications match. Try a parameter name or a unit.
Recommended operation is distinct from absolute stress limits.
Thresholds and output levels
25°C · stated test conditions
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Trigger at 5 V | 1.67 V typical; 1.1–2.2 V limits | Each channel |
| Threshold at 5 V | 3.3 V typical; 2.4–4.2 V limits | Each channel |
| LOW output | 0.1 V typical; 0.25 V maximum | 5 V supply; sinking 5 mA |
| HIGH output | 3.3 V typical; 2.75 V minimum | 5 V supply; sourcing 100 mA |
| Supply current | 6 mA typical; 12 mA maximum | 5 V; outputs LOW; no external load |
No specifications match. Try a parameter name or a unit.
These test points must not be extrapolated to every load or temperature.
Timing equations
Nominal RC relationships
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Astable HIGH | ln(2) × (RA + RB) × C | Capacitor charges through both resistors |
| Astable LOW | ln(2) × RB × C | Capacitor discharges through RB |
| Frequency | 1 / [ln(2) × (RA + 2RB) × C] | Use Ω, F and seconds |
| HIGH duty cycle | (RA + RB) / (RA + 2RB) | Above 50% in the ordinary two-resistor circuit |
| Monostable pulse | Approximately 1.1 × R × C | Trigger must return HIGH before the timing interval ends |
No specifications match. Try a parameter name or a unit.
Ideal ratios assume unmodulated CONT. The initial power-on interval differs from steady-state cycles.
Two-clock circuit
5 V · independent outputs
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| RA1 / RA2 | 10 kΩ | VCC to respective DISCH pin |
| RB1 / RB2 | 100 kΩ | DISCH to respective timing node |
| C1 | 10 µF | Timing node 1 to GND; positive terminal to timing node |
| C2 | 1 µF | Timing node 2 to GND; positive terminal to timing node |
| Nominal f1 / f2 | 0.687 Hz / 6.87 Hz | Ideal values; component tolerances omitted |
| HIGH duty cycle | 52.38% | Both channels |
| Control bypass | 10 nF per channel | Pins 3 and 11 to GND |
| Reset | Pins 4 and 10 to +5 V | Neither input floats |
No specifications match. Try a parameter name or a unit.
The illustrated scope is a high-impedance load. Use a series resistor for any LED.
Control behavior
Applied independently to each timer
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| RESET LOW | OUT LOW; DISCH conducting | Overrides other inputs |
| TRIG below lower reference | OUT HIGH; DISCH open | When RESET is inactive |
| THRES above upper reference | OUT LOW; DISCH conducting | When trigger is above its reference |
| Both timing inputs between references | Retain latch state | Hysteresis prevents chatter in a clean RC cycle |
| Unused channel | Hold RESET LOW and define its inputs | Do not assume floating pins are harmless |
No specifications match. Try a parameter name or a unit.
Input priority follows RESET, then trigger, then threshold.
Package and pin reference
NE556N · PDIP-14
Manufacturer specifications 5 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Pitch | 2.54 mm | Through-hole |
| Timer 1 | DISCH 1; THRES 2; CONT 3 | RESET 4; OUT 5; TRIG 6 |
| Timer 2 | TRIG 8; OUT 9; RESET 10 | CONT 11; THRES 12; DISCH 13 |
| Shared power | GND 7; VCC 14 | Never reuse the eight-pin NE555 numbering |
| Orientation | Top view | Pin-one mark and notch identify the numbering |
No specifications match. Try a parameter name or a unit.
Match the exact mechanical package before manufacturing a PCB.
Connections by function
Select a pin for its function, connection guidance and electrical notes.