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LM555 Timer — Parsed Datasheet

Source: TI LM555 Datasheet (SNAS548D)
Manufacturer: Texas Instruments
Document: SNAS548D — Rev D, January 2015
Part Number: LM555

Description

The LM555 is a highly stable device for generating accurate time delays or oscillation. Additional terminals are provided for triggering or resetting if desired. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor. For astable operation as an oscillator, the free running frequency and duty cycle are accurately controlled with two external resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output circuit can source or sink up to 200 mA or drive TTL circuits.

Key Specifications

Parameter	Value
Supply Voltage	4.5V – 16V
Output Current	200 mA (source or sink)
Pin Count	8
Supply Current	3–15 mA
Temperature Stability	0.005%/°C
Rise / Fall Time	100 ns
ESD Rating (HBM)	±500V

Features

Direct replacement for SE555/NE555
Timing from microseconds through hours
Operates in both astable and monostable modes
Adjustable duty cycle
Output can source or sink 200 mA
Output and supply TTL compatible
Temperature stability better than 0.005% per °C
Normally on and normally off output
Available in 8-pin VSSOP package

Pin Configuration

Pin	Name	Direction	Description
1	GND	GND	Ground reference voltage (0V)
2	TRIGGER	IN	Triggers on voltage falling below 1/3 VCC. Responsible for flip-flop set-to-reset transition.
3	OUTPUT	OUT	Output driven waveform. Can source or sink up to 200 mA. TTL compatible.
4	RESET	IN	Active low reset. Connect to VCC when not used to avoid false triggering. Threshold 0.4–1V.
5	CONTROL VOLTAGE	IN	Controls threshold/trigger levels. Determines pulse width. Typically bypassed with 10nF to GND.
6	THRESHOLD	IN	Compares applied voltage with 2/3 VCC reference. Sets the internal flip-flop. Input current 0.1–0.25 µA.
7	DISCHARGE	IN	Open collector output. Discharges timing capacitor between intervals.
8	VCC	PWR	Positive supply voltage 4.5V to 16V. Bypass with 100nF ceramic.

Absolute Maximum Ratings

Parameter	Min	Max	Unit
Supply Voltage (VCC)	—	18	V
Power Dissipation — LM555CM/CN	—	1180	mW
Power Dissipation — LM555CMM (VSSOP)	—	613	mW
Storage Temperature	−65	150	°C
ESD — Human Body Model (HBM)	—	±500	V

Recommended Operating Conditions

Parameter	Min	Max	Unit
Supply Voltage	4.5	16	V
Operating Temperature (TA)	0	70	°C

Thermal Information

Package	RθJA (°C/W)
PDIP-8	106
SOIC-8	170
VSSOP-8	204

Electrical Characteristics

TA = 25°C, VCC = 5V to 15V, unless otherwise specified.

Parameter	Conditions	Min	Typ	Max	Unit
Supply Voltage	—	4.5	—	16	V
Supply Current	VCC=5V, RL=∞	—	3	6	mA
Supply Current	VCC=15V, RL=∞	—	10	15	mA
Threshold Voltage	—	—	0.667×VCC	—	V
Trigger Voltage	VCC=15V	—	5	—	V
Trigger Voltage	VCC=5V	—	1.67	—	V
Trigger Current	—	—	0.5	0.9	µA
Reset Voltage	—	—	0.5	1	V
Reset Current	—	—	0.1	0.4	mA
Threshold Current	—	—	0.1	0.25	µA
Control Voltage	VCC=15V	9	10	11	V
Control Voltage	VCC=5V	2.6	3.33	4	V
Pin 7 Leakage (High)	—	—	1	100	nA
Pin 7 Saturation	VCC=15V, I7=15mA	—	—	180	mV
Output Low (VOL)	ISINK=10mA	—	0.1	0.25	V
Output Low (VOL)	ISINK=50mA	—	0.4	0.75	V
Output Low (VOL)	ISINK=100mA	—	2	2.5	V
Output High (VOH)	ISRC=100mA, VCC=15V	12.75	—	13.3	V
Output High (VOH)	ISRC=100mA, VCC=5V	2.75	—	3.3	V
Rise Time	—	—	100	—	ns
Fall Time	—	—	100	—	ns

Timing Accuracy

Parameter	Mode	Value	Unit
Initial Accuracy	Monostable	1%	—
Drift with Temperature	Monostable	50	ppm/°C
Accuracy over Temperature	Monostable	1.5%	—
Drift with Supply	Monostable	0.1%	/V
Initial Accuracy	Astable	2.25%	—
Drift with Temperature	Astable	150	ppm/°C
Accuracy over Temperature	Astable	3%	—
Drift with Supply	Astable	0.30%	/V

Packages

Package	Body Size	RθJA
SOIC-8 (LM555CM)	4.90 × 3.91 mm	170 °C/W
PDIP-8 (LM555CN)	9.81 × 6.35 mm	106 °C/W
VSSOP-8 (LM555CMM)	3.00 × 3.00 mm	204 °C/W

Applications

Precision Timing
Pulse Generation
Sequential Timing
Time Delay Generation
Pulse Width Modulation (PWM)
Pulse Position Modulation
Linear Ramp Generator

Key Formulas

Monostable (One-Shot) — Time Delay:
t = 1.1 × RA × C

Astable — Frequency:
f = 1.44 / ((RA + 2·RB) × C)

Astable — Duty Cycle:
D = (RA + RB) / (RA + 2·RB)

Conditions: RA = 1kΩ to 100kΩ, C = 0.1µF. Maximum total RA + RB = 20MΩ for 15V operation.

Diagrams

20 figures extracted from the datasheet PDF. See attached image assets.

Circuit Diagrams

schematic-internal.png — Complete transistor-level schematic (28 transistors, 12 resistors)
circuit-monostable.png — Monostable (one-shot) application circuit
circuit-astable.png — Astable (oscillator) application circuit
circuit-monostable-example.png — Practical monostable with pushbutton + LED

Electrical Characteristics

char-supply-current-vs-voltage.png — ICC vs VCC across temperature
char-vout-high-drop-vs-isource.png — Output high voltage drop vs source current
char-vout-low-vs-isink-5v.png — Output low voltage at VCC=5V
char-vout-low-vs-isink-10v.png — Output low voltage at VCC=10V
char-vout-low-vs-isink-15v.png — Output low voltage at VCC=15V
char-min-trigger-pulse.png — Minimum trigger pulse width
char-discharge-vsat-15v.png — Pin 7 saturation voltage at VCC=15V
char-discharge-vsat-5v.png — Pin 7 saturation voltage at VCC=5V
char-prop-delay-multi-vcc.png — Propagation delay vs trigger (multi-VCC)
char-prop-delay-multi-temp.png — Propagation delay vs trigger (multi-temperature)

Waveforms

waveform-astable-3ch.png — Astable mode: output + trigger + capacitor
waveform-astable-2ch.png — Astable mode: output + capacitor sawtooth
waveform-monostable.png — Monostable mode: output + reset + capacitor
waveform-oscilloscope-color.png — Real oscilloscope capture (3-channel, color)

Design Charts

chart-monostable-time-delay.png — Capacitance vs time delay nomograph
chart-astable-frequency.png — Capacitance vs frequency nomograph

Files

🖼 char-supply-current-vs-voltage.png Image 🖼 char-vout-high-drop-vs-isource.png Image 🖼 chart-astable-frequency.png Image 🖼 chart-monostable-time-delay.png Image 🖼 circuit-astable.png Image 🖼 circuit-monostable.png Image 🌐 lm555-parsed.html Web Page 🖼 schematic-internal.png Image 🖼 waveform-astable-3ch.png Image 🖼 waveform-oscilloscope-color.png Image