SLFS023H April   1978  – December 2024 NA556 , NE556 , SA556 , SE556

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Switching Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Monostable Operation
      2. 6.3.2 Astable Operation
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Pulse-Width Modulation
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
        3. 7.2.1.3 Application Curve
      2. 7.2.2 Pulse-Position Modulation
        1. 7.2.2.1 Design Requirements
        2. 7.2.2.2 Detailed Design Procedure
        3. 7.2.2.3 Application Curves
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|14
  • DB|14
  • N|14
  • NS|14
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6.3.2 Astable Operation

As shown in Figure 6-3, adding a second resistor, RB, to the circuit of Figure 6-2 and connecting the trigger input to the threshold input causes the timer to self-trigger and run as a multivibrator. The capacitor CT charges through RA and RB and then discharges through RB only. Therefore, the duty cycle is controlled by the values of RA and RB.

This astable connection results in capacitor CT charging and discharging between the threshold-voltage level
(≅ 0.67 × VCC) and the trigger-voltage level (≅ 0.33 × VCC). As in the monostable circuit, charge and discharge times (and, therefore, the frequency and duty cycle) are independent of the supply voltage. To reduce distortion, use at maximum frequency of 100kHz or below. If higher-frequency operation is required, consider using the TLC556 LinCMOS™ Timer instead.

NA556 NE556 SA556 SE556 Circuit for Astable Operation
Decouple CONT voltage to ground with a capacitor to improve operation. Reevaluate for individual applications.
Figure 6-3 Circuit for Astable Operation
Equation 1. t H ≅ 0.693 × R A + R B × C T
Equation 2. t L ≅ 0.693 × R B × C T

Other useful relationships for period, frequency, and driver-referred and waveform-referred duty cycle are shown as follows:

Equation 3. T = t H + t L ≅ 0.693 × R A + 2 R B × C T
Equation 4. f = 1 T ≅ 1.44 R A + 2 R B × C T
Equation 5. O u t p u t   d r i v e r   d u t y   c y c l e = t L T ≅ R B R A + 2 R B
Equation 6. O u t p u t   w a v e f o r m   d u t y   c y c l e = t H T ≅ 1 - R B R A + 2 R B = R A + R B R A + 2 R B