LM555CMX

Product Folder Sample & Buy Support & Community Tools & Software Technical Documents LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 LM555 Timer 1 Features 3 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 a stable 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. 1 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 2 Applications • • • • • • • Precision Timing Pulse Generation Sequential Timing Time Delay Generation Pulse Width Modulation Pulse Position Modulation Linear Ramp Generator Device Information(1) PART NUMBER LM555 PACKAGE BODY SIZE (NOM) SOIC (8) 4.90 mm × 3.91 mm PDIP (8) 9.81 mm × 6.35 mm VSSOP (8) 3.00 mm × 3.00 mm (1) For all available packages, see the orderable addendum at the end of the datasheet. Schematic Diagram 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 4 6.1 6.2 6.3 6.4 6.5 6.6 4 4 4 4 5 6 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information ................................................. Electrical Characteristics .......................................... Typical Characteristics .............................................. 7.3 Feature Description................................................... 8 7.4 Device Functional Modes.......................................... 9 8 Application and Implementation ........................ 12 8.1 Application Information............................................ 12 8.2 Typical Application ................................................. 12 9 Power Supply Recommendations...................... 15 10 Layout................................................................... 15 10.1 Layout Guidelines ................................................. 15 10.2 Layout Example .................................................... 15 11 Device and Documentation Support ................. 16 Detailed Description .............................................. 8 11.1 Trademarks ........................................................... 16 11.2 Electrostatic Discharge Caution ............................ 16 11.3 Glossary ................................................................ 16 7.1 Overview ................................................................... 8 7.2 Functional Block Diagram ......................................... 8 12 Mechanical, Packaging, and Orderable Information ........................................................... 16 4 Revision History Changes from Revision C (March 2013) to Revision D • Added Pin Configuration and Functions section, ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section .............................. 1 Changes from Revision B (March 2013) to Revision C • 2 Page Page Changed layout of National Data Sheet to TI format ........................................................................................................... 13 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 LM555 www.ti.com SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 5 Pin Configuration and Functions D, P, and DGK Packages 8-Pin PDIP, SOIC, and VSSOP Top View 1 GND 8 2 TRIGGER 3 OUTPUT 7 COMPARATOR R FLIP FLOP R OUTPUT STAGE R DISCHARGE COMPARATOR VREF (INT) 4 RESET +VCC 6 THRESHOLD 5 CONTROL VOLTAGE Pin Functions PIN NO. NAME 5 Control Voltage 7 Discharge I/O DESCRIPTION I Controls the threshold and trigger levels. It determines the pulse width of the output waveform. An external voltage applied to this pin can also be used to modulate the output waveform I Open collector output which discharges a capacitor between intervals (in phase with output). It toggles the output from high to low when voltage reaches 2/3 of the supply voltage 1 GND O Ground reference voltage 3 Output O Output driven waveform I Negative pulse applied to this pin to disable or reset the timer. When not used for reset purposes, it should be connected to VCC to avoid false triggering I Compares the voltage applied to the terminal with a reference voltage of 2/3 Vcc. The amplitude of voltage applied to this terminal is responsible for the set state of the flip-flop I Responsible for transition of the flip-flop from set to reset. The output of the timer depends on the amplitude of the external trigger pulse applied to this pin I Supply voltage with respect to GND 4 6 2 8 Reset Threshold Trigger V+ Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 3 LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) (2) MIN Power Dissipation (3) Soldering Information MAX UNIT LM555CM, LM555CN (4) 1180 mW LM555CMM 613 mW PDIP Package Soldering (10 Seconds) 260 °C Small Outline Packages (SOIC and VSSOP) Vapor Phase (60 Seconds) 215 °C 220 °C 150 °C Infrared (15 Seconds) Storage temperature, Tstg (1) (2) (3) (4) –65 Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. If Military/Aerospace specified devices are required, please contact the TI Sales Office/Distributors for availability and specifications. For operating at elevated temperatures the device must be derated above 25°C based on a 150°C maximum junction temperature and a thermal resistance of 106°C/W (PDIP), 170°C/W (S0IC-8), and 204°C/W (VSSOP) junction to ambient. Refer to RETS555X drawing of military LM555H and LM555J versions for specifications. 6.2 ESD Ratings V(ESD) (1) (2) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) VALUE UNIT ±500 (2) V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. The ESD information listed is for the SOIC package. 6.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) MIN Supply Voltage Temperature, TA 0 Operating junction temperature, TJ MAX UNIT 18 V 70 °C 70 °C 6.4 Thermal Information LM555 THERMAL METRIC (1) PDIP SOIC VSSOP UNIT 204 °C/W 8 PINS RθJA (1) 4 Junction-to-ambient thermal resistance 106 170 For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 LM555 www.ti.com SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 6.5 Electrical Characteristics (TA = 25°C, VCC = 5 V to 15 V, unless otherwise specified) (1) (2) PARAMETER TEST CONDITIONS Supply Voltage Supply Current MIN TYP 4.5 MAX UNIT 16 VCC = 5 V, RL = ∞ 3 6 VCC = 15 V, RL = ∞ (Low State) (3) 10 15 V mA Timing Error, Monostable Initial Accuracy Drift with Temperature 1% RA = 1 k to 100 kΩ, C = 0.1 μF, 50 ppm/°C (4) Accuracy over Temperature 1.5 % Drift with Supply 0.1 % V Timing Error, Astable Initial Accuracy Drift with Temperature 2.25 RA, RB =1 k to 100 kΩ, C = 0.1 μF, 150 Accuracy over Temperature 3.0% Drift with Supply 0.30 % Threshold Voltage 0.667 Trigger Voltage VCC = 15 V 0.4 Reset Current Control Voltage Level VCC = 5 V Pin 7 Leakage Output High Pin 7 Sat V 0.5 0.9 μA 0.5 1 V 0.1 0.4 mA 0.1 0.25 μA 9 10 11 2.6 3.33 4 1 100 (5) VCC = 15 V V 1.67 Trigger Current Reset Voltage /V x VCC 5 VCC = 5 V Threshold Current ppm/°C (4) V nA (6) Output Low VCC = 15 V, I7 = 15 mA 180 Output Low VCC = 4.5 V, I7 = 4.5 mA 80 200 mV ISINK = 10 mA 0.1 0.25 V ISINK = 50 mA Output Voltage Drop (Low) mV VCC = 15 V 0.4 0.75 V ISINK = 100 mA 2 2.5 V ISINK = 200 mA 2.5 V VCC = 5 V ISINK = 8 mA ISINK = 5 mA (1) (2) (3) (4) (5) (6) V 0.25 0.35 V All voltages are measured with respect to the ground pin, unless otherwise specified. Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Recommended Operating Conditions indicate conditions for which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which ensures specific performance limits. This assumes that the device is within the Recommended Operating Conditions. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device performance. Supply current when output high typically 1 mA less at VCC = 5 V. Tested at VCC = 5 V and VCC = 15 V. This will determine the maximum value of RA + RB for 15 V operation. The maximum total (RA + RB) is 20 MΩ. No protection against excessive pin 7 current is necessary providing the package dissipation rating will not be exceeded. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 5 LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com Electrical Characteristics (continued) (TA = 25°C, VCC = 5 V to 15 V, unless otherwise specified)(1)(2) PARAMETER Output Voltage Drop (High) TEST CONDITIONS MIN ISOURCE = 200 mA, VCC = 15 V TYP MAX UNIT 12.5 V 12.75 13.3 V 2.75 3.3 V Rise Time of Output 100 ns Fall Time of Output 100 ns ISOURCE = 100 mA, VCC = 15 V VCC = 5 V 6.6 Typical Characteristics 6 Figure 1. Minimum Pulse Width Required For Triggering Figure 2. Supply Current vs. Supply Voltage Figure 3. High Output Voltage vs. Output Source Current Figure 4. Low Output Voltage vs. Output Sink Current Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 LM555 www.ti.com SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 Typical Characteristics (continued) Figure 5. Low Output Voltage vs. Output Sink Current Figure 6. Low Output Voltage vs. Output Sink Current Figure 7. Output Propagation Delay vs. Voltage Level of Trigger Pulse Figure 8. Output Propagation Delay vs. Voltage Level of Trigger Pulse Figure 9. Discharge Transistor (Pin 7) Voltage vs. Sink Current Figure 10. Discharge Transistor (Pin 7) Voltage vs. Sink Current Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 7 LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com 7 Detailed Description 7.1 Overview 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 200mA or driver TTL circuits. The LM555 are available in 8-pin PDIP, SOIC, and VSSOP packages and is a direct replacement for SE555/NE555. 7.2 Functional Block Diagram CONTROL THRESHOLD VOLTAGE +Vcc COMPARATOR RESET Vref (int) TRIGGER FLIP FLOP DISCHARGE COMPARATOR OUTPUT STAGE OUTPUT 7.3 Feature Description 7.3.1 Direct Replacement for SE555/NE555 The LM555 timer is a direct replacement for SE555 and NE555. It is pin-to-pin compatible so that no schematic or layout changes are necessary. The LM555 come in an 8-pin PDIP, SOIC, and VSSOP package. 7.3.2 Timing From Microseconds Through Hours The LM555 has the ability to have timing parameters from the microseconds range to hours. The time delay of the system can be determined by the time constant of the R and C value used for either the monostable or astable configuration. A nomograph is available for easy determination of R and C values for various time delays. 7.3.3 Operates in Both Astable and Monostable Mode The LM555 can operate in both astable and monostable mode depending on the application requirements. • Monostable mode: The LM555 timer acts as a “one-shot” pulse generator. The pulse beings when the LM555 timer receives a signal at the trigger input that falls below a 1/3 of the voltage supply. The width of the output pulse is determined by the time constant of an RC network. The output pulse ends when the voltage on the 8 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 LM555 www.ti.com SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 Feature Description (continued) • capacitor equals 2/3 of the supply voltage. The output pulse width can be extended or shortened depending on the application by adjusting the R and C values. Astable (free-running) mode: The LM555 timer can operate as an oscillator and puts out a continuous stream of rectangular pulses having a specified frequency. The frequency of the pulse stream depends on the values of RA, RB, and C. 7.4 Device Functional Modes 7.4.1 Monostable Operation In this mode of operation, the timer functions as a one-shot (Figure 11). The external capacitor is initially held discharged by a transistor inside the timer. Upon application of a negative trigger pulse of less than 1/3 VCC to pin 2, the flip-flop is set which both releases the short circuit across the capacitor and drives the output high. Figure 11. Monostable The voltage across the capacitor then increases exponentially for a period of t = 1.1 RA C, at the end of which time the voltage equals 2/3 VCC. The comparator then resets the flip-flop which in turn discharges the capacitor and drives the output to its low state. Figure 12 shows the waveforms generated in this mode of operation. Since the charge and the threshold level of the comparator are both directly proportional to supply voltage, the timing interval is independent of supply. VCC = 5 V TIME = 0.1 ms/DIV. RA = 9.1 kΩ C = 0.01 μF Top Trace: Input 5V/Div. Middle Trace: Output 5V/Div. Bottom Trace: Capacitor Voltage 2V/Div. Figure 12. Monostable Waveforms During the timing cycle when the output is high, the further application of a trigger pulse will not effect the circuit so long as the trigger input is returned high at least 10 μs before the end of the timing interval. However the circuit can be reset during this time by the application of a negative pulse to the reset terminal (pin 4). The output will then remain in the low state until a trigger pulse is again applied. When the reset function is not in use, TI recommends connecting the Reset pin to VCC to avoid any possibility of false triggering. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 9 LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com Device Functional Modes (continued) Figure 13 is a nomograph for easy determination of R, C values for various time delays. Figure 13. Time Delay 7.4.2 Astable Operation If the circuit is connected as shown in Figure 14 (pins 2 and 6 connected) it will trigger itself and free run as a multivibrator. The external capacitor charges through RA + RB and discharges through RB. Thus the duty cycle may be precisely set by the ratio of these two resistors. Figure 14. Astable In this mode of operation, the capacitor charges and discharges between 1/3 VCC and 2/3 VCC. As in the triggered mode, the charge and discharge times, and therefore the frequency are independent of the supply voltage. Figure 15 shows the waveforms generated in this mode of operation. 10 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 LM555 www.ti.com SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 Device Functional Modes (continued) VCC = 5 V TIME = 20μs/DIV. RA = 3.9 kΩ RB = 3 kΩ C = 0.01 μF Top Trace: Output 5V/Div. Bottom Trace: Capacitor Voltage 1V/Div. Figure 15. Astable Waveforms The charge time (output high) is given by: t1 = 0.693 (RA + RB) C (1) And the discharge time (output low) by: t2 = 0.693 (RB) C (2) Thus the total period is: T = t1 + t2 = 0.693 (RA +2RB) C (3) The frequency of oscillation is: (4) Figure 16 may be used for quick determination of these RC values. The duty cycle is: (5) Figure 16. Free Running Frequency Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 11 LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information The LM555 timer can be used a various configurations, but the most commonly used configuration is in monostable mode. A typical application for the LM555 timer in monostable mode is to turn on an LED for a specific time duration. A pushbutton is used as the trigger to output a high pulse when trigger pin is pulsed low. This simple application can be modified to fit any application requirement. 8.2 Typical Application Figure 17 shows the schematic of the LM555 that flashes an LED in monostable mode. Figure 17. Schematic of Monostable Mode to Flash an LED 8.2.1 Design Requirements The main design requirement for this application requires calculating the duration of time for which the output stays high. The duration of time is dependent on the R and C values (as shown in Figure 17) and can be calculated by: t = 1.1 × R × C seconds (6) 8.2.2 Detailed Design Procedure To allow the LED to flash on for a noticeable amount of time, a 5 second time delay was chosen for this application. By using Equation 6, RC equals 4.545. If R is selected as 100 kΩ, C = 45.4 µF. The values of R = 100 kΩ and C = 47 µF was selected based on standard values of resistors and capacitors. A momentary push button switch connected to ground is connected to the trigger input with a 10-K current limiting resistor pullup to the supply voltage. When the push button is pressed, the trigger pin goes to GND. An LED is connected to the output pin with a current limiting resistor in series from the output of the LM555 to GND. The reset pin is not used and was connected to the supply voltage. 8.2.2.1 Frequency Divider The monostable circuit of Figure 11 can be used as a frequency divider by adjusting the length of the timing cycle. Figure 18 shows the waveforms generated in a divide by three circuit. 12 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 LM555 www.ti.com SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 Typical Application (continued) VCC = 5 V Top Trace: Input 4 V/Div. TIME = 20 μs/DIV. Middle Trace: Output 2V/Div. RA = 9.1 kΩ Bottom Trace: Capa citor 2V/Div. C = 0.01 μF Figure 18. Frequency Divider 8.2.2.2 Additional Information Lower comparator storage time can be as long as 10 μs when pin 2 is driven fully to ground for triggering. This limits the monostable pulse width to 10 μs minimum. Delay time reset to output is 0.47 μs typical. Minimum reset pulse width must be 0.3 μs, typical. Pin 7 current switches within 30 ns of the output (pin 3) voltage. 8.2.3 Application Curves The data shown below was collected with the circuit used in the typical applications section. The LM555 was configured in the monostable mode with a time delay of 5.17 s. The waveforms correspond to: • Top Waveform (Yellow) – Capacitor voltage • Middle Waveform (Green) – Trigger • Bottom Waveform (Purple) – Output As the trigger pin pulses low, the capacitor voltage starts charging and the output goes high. The output goes low as soon as the capacitor voltage reaches 2/3 of the supply voltage, which is the time delay set by the R and C value. For this example, the time delay is 5.17 s. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 13 LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com Typical Application (continued) Figure 19. Trigger, Capacitor Voltage, and Output Waveforms in Monostable Mode 14 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 LM555 www.ti.com SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 9 Power Supply Recommendations The LM555 requires a voltage supply within 4.5 V to 16 V. Adequate power supply bypassing is necessary to protect associated circuitry. The minimum recommended capacitor value is 0.1 μF in parallel with a 1-μF electrolytic capacitor. Place the bypass capacitors as close as possible to the LM555 and minimize the trace length. 10 Layout 10.1 Layout Guidelines Standard PCB rules apply to routing the LM555. The 0.1-µF capacitor in parallel with a 1-µF electrolytic capacitor should be as close as possible to the LM555. The capacitor used for the time delay should also be placed as close to the discharge pin. A ground plane on the bottom layer can be used to provide better noise immunity and signal integrity. Figure 20 is the basic layout for various applications. • C1 – based on time delay calculations • C2 – 0.01-µF bypass capacitor for control voltage pin • C3 – 0.1-µF bypass ceramic capacitor • C4 – 1-µF electrolytic bypass capacitor • R1 – based on time delay calculations • U1 – LMC555 10.2 Layout Example Figure 20. Layout Example Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 15 LM555 SNAS548D – FEBRUARY 2000 – REVISED JANUARY 2015 www.ti.com 11 Device and Documentation Support 11.1 Trademarks All trademarks are the property of their respective owners. 11.2 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 11.3 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 16 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: LM555 PACKAGE OPTION ADDENDUM www.ti.com 27-May-2022 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (°C) Device Marking (3) Samples (4/5) (6) LM555CM NRND SOIC D 8 95 Non-RoHS & Green Call TI Level-1-235C-UNLIM 0 to 70 LM 555CM LM555CM/NOPB ACTIVE SOIC D 8 95 RoHS & Green SN Level-1-260C-UNLIM 0 to 70 LM 555CM LM555CMM NRND VSSOP DGK 8 1000 Non-RoHS & Green Call TI Level-1-260C-UNLIM 0 to 70 Z55 LM555CMM/NOPB ACTIVE VSSOP DGK 8 1000 RoHS & Green SN Level-1-260C-UNLIM 0 to 70 Z55 Samples LM555CMMX/NOPB ACTIVE VSSOP DGK 8 3500 RoHS & Green SN Level-1-260C-UNLIM 0 to 70 Z55 Samples LM555CMX NRND SOIC D 8 2500 Non-RoHS & Green Call TI Level-1-235C-UNLIM 0 to 70 LM 555CM LM555CMX/NOPB ACTIVE SOIC D 8 2500 RoHS & Green SN Level-1-260C-UNLIM 0 to 70 LM 555CM Samples LM555CN/NOPB ACTIVE PDIP P 8 40 RoHS & Green NIPDAU Level-1-NA-UNLIM 0 to 70 LM 555CN Samples (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of