NE555_12 STMICROELECTRONICS | Alldatasheet

Document overview

  • Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
  • PDF pages: 20

Technical content

Features

■ Low turn-off time ■ Maximum operating frequency greater than 500 kHz ■ Timing from microseconds to hours ■ Operates in both astable and monostable modes ■ Output can source or sink up to 200 mA ■ Adjustable duty cycle ■ TTL compatible ■ Temperature stability of 0.005% per °C

Description

The NE555, SA555, and SE555 monolithic timing circuits are highly stable controllers capable of producing accurate time delays or oscillation. 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 the duty cycle are both accurately controlled with two external resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output structure can source or sink up to 200 mA. 4 5 N DIP8 (Plastic package) D SO8 (Plastic micropackage) 1 - GND 2 - Trigger 3 - Output 4 - Reset 5 - Control voltage 6 - Threshold 7 - Discharge 8 - V CC Pin connections (top view)

1 Schematic diagrams

Figure 1. Block diagram Figure 2. Schematic diagram

2 Absolute maximum ratings and operating conditions

Table 1. Absolute maximum ratings

  1. Short-circuits can c ause excessive heating. These values are typical.
  2. Human body model: a 100 pF capacit or is charged to the specified voltage, then discharged through a

while the other pins are floating.

  1. Machine model: a 200 pF capacitor is charged to the specified voltage, then discharged directly between

connected pin combinations while the other pins are floating.

  1. Charged device model: all pins and the package are charged together to the specified voltage and then

discharged directly to the ground through only one pin. This is done for all pins. Table 2. Operating conditions

3 Electrical characteristics

Table 3. T amb = +25° C, VCC = +5 V to +15 V (unless otherwise specified)

  1. Tested at V CC = +5 V and VCC = +15 V.
  2. This will determine th e maximum value of RA + RB for 15 V operation. The maximum total (RA + RB) is 20 MΩ for +15 V

operation and 3.5 MΩ for +5 V operation.

  1. Specified with trigger input high.
  2. No protection against excessive pin 7 current is necessary, providing the package dissipation rating is not exceeded.
  3. Time measured from a positive pulse (from 0 V to 0.8 x V CC) on the threshold pin to the transition from high to low on the

output pin. Trigger is tied to threshold. Table 3. T amb = +25° C, VCC = +5 V to +15 V (unless otherwise specified) (continued)

4 Application information

4.1 Monostable operation

external capacitor is initially held discharged by a transistor inside the timer. Figure 12. Typical schematics in monostable operation is easily determined by Figure 14. during the timing cycle discharges the external capacitor and causes the cycle to start over. pulse is applied, the output is driven to its LOW state. capacitor rapidly and drives the output to its LOW state. Figure 13 shows the actual waveforms generated in this mode of operation.

Figure 13. Waveforms in monostable operation Figure 14. Pulse duration versus R1C1

4.2 Astable operation

ratio of these two resistors. In the astable mode of operation, C1 charges and discharges between 1/3 VCC and 2/3 VCC. independent of the supply voltage.

4.3 Pulse width modulator

Figure 18. Pulse width modulator

4.4 Linear ramp

Figure 19. Linear ramp

Figure 21. 50% duty cycle oscillator and RB cannot bring pin 2 down to 1/3 VCC and trigger the lower comparator.

4.6 Additional information

minimum recommended is 0.1 µF in parallel with 1 µF electrolytic.

5 Package information

In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK® specifications, grade definitions and product status are available at: www.st.com. ECOPACK® is an ST trademark.

5.1 DIP8 package information

Figure 22. DIP8 package mechanical drawing Table 4. DIP8 package mechanical data

5.2 SO-8 package information

Figure 23. SO-8 package mechanical drawing Table 5. SO-8 package mechanical data

6 Ordering information

Table 6. Order codes

  1. Not recommended for new design. Contact local ST sales office for availability.

7 Revision history

Table 7. Document revision history 01-Jun-2003 1 Initial release. 15-Mar-2007 4 Expanded order code table. Table 2: Operating conditions. Table 1: Absolute maximum ratings. Modified duty cycle equation in Section 4.2: Astable operation. Updated ECOPACK® text in Section 5: Package information. tubes is not recommended for new design.