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| INTEGRATED CIRCUITS www..com AN171 NE558 applications 1988 Dec Philips Semiconductors Philips Semiconductors Application note www..com NE558 applications AN171 INTRODUCTION The 558 is a monolithic Quad Timer designed to be used in the timing range from a few microseconds to a few hours. Four entirely independent timing functions can be achieved using a timing resistor and capacitor for each section. Two sections of the quad may be interconnected for astable operation. All four sections may be used together, in tandem, for sequential timing applications up to several hours. No coupling capacitors are required when connecting the output of one timer section to the input of the next. disabled. After reset is finished, the trigger voltage must be taken high and then low to implement triggering. The reset voltage must be brought below 0.8V to insure reset. THE CONTROL VOLTAGE The control voltage is also made available on the 558 timer. This allows the threshold VCC FEATURES RESET S1 * 100mA output current per section * Edge-triggered (no coupling capacitor) * Output independent of trigger conditions * Wide supply voltage range 4.5V to 16V * Timer intervals from microseconds to hours * Time period equals RC CIRCUIT OPERATIONS In the one-shot mode of operation, it is necessary to supply a minimum of two external components (the resistor and capacitor) for timing. The time period is equal to the product of R and C. An output load must be present to complete the circuit due to the output structure of the 558. For astable operation, it is desirable to cross-couple two devices from the 558 Quad. The outputs are direct-coupled to the opposite trigger input. The duty cycle can be set by the ratio of R1C1 to R2C2, from close to zero to almost 100%. An astable circuit using one timer is shown in Figure 5b. VCC R1 C1 C2 R2 2 7 5 13 3 1 6 8 TR1 TR2 RL2 TR3 TR4 RL4 RL3 S2 RL1 LOAD SWITCH (558) (559) C3 10 C4 15 4 R4 R3 12 11 9 14 16 SL00990 Figure 1. 558 Test Circuit voltage to be modulated, therefore controlling the output pulse width and duty cycle with an external control voltage. The range of this control voltage is from about 0.5V to VCC minus 1V. This will give a cycle time variation of about 50:1. In a sequential timer with voltage-controlled cycle time, the timing periods remain proportional over the adjustment range. TEST BOARD FOR 558 OUTPUT STRUCTURE 558 The 558 structure is open-collector which requires a pull-up resistor to VCC and is capable of sinking 100mA per unit, but not to exceed the power dissipation and junction temperature rating of the die and package. The output is normally low and is switched high when triggered. The circuit layout can be used to test and characterize the 558 timer. S2 is used to connect the loads to either VCC or ground. The main precaution, in layout of the 558 circuit, is the path of the discharge current from the timing capacitor to ground (Pin 12). The path must be direct to Pin 12 and not on the ground bus. This is to prevent voltage spikes on the ground bus return due to current switching transient. It is also wise to use good power supply bypassing when large currents are being switched. RESET A reset function has been made available to reset all sections simultaneously to an output low state. During reset the trigger is December 1988 2 Philips Semiconductors Application note www..com NE558 applications AN171 RESET V+0 V+ R1 V+0 R2 R4 C1 C3 SI GND R3 2.2F C2 RL2 C4 LOAD V + (558) GND (559) RL3 INPUTS 1 OUTPUTS 1 2 2 3 3 4 4 a. Test Board Layout b. Foil Side Figure 2. VCC R T C RL T R C RL T R C RL T R C TRIGGER T 4(RC) - 2 HRS TRIGGER TR 0 TR 0 TR 0 TR 0 OUTPUT RL SL00991 OUTPUT SL00992 Figure 3. 558 Two-Hour Timer December 1988 3 Philips Semiconductors Application note www..com NE558 applications AN171 TRIGGER VCC R1 TRIGGER VCC T TR 0 CV OUTPUT 1 C1 RL R1 T TR 0 CV OUTPUT 2 C2 RL R1 T TR 0 CV OUTPUT 3 C3 RL R1 T TR 0 CV OUTPUT 3 ADJ UP 50: 1 RANGE OUTPUT 4 OUTPUT 4 OUTPUT 2 C4 RL OUTPUT 1 OUTPUT NOTE: t1, t2, t3, t4 remain proportional over entire adj. range. SL00993 Figure 4. 558 Sequential Timer With Voltage-Controlled Cycle Time (50:1 Range) VCC VCC R RL TRIGGER TR 0 T C TR 0 T C1 TR 0 C2 T R1 RL R2 NOTE: T = RC OUTPUT OUTPUT a. Monostable Operation (One-Shot) VCC b. 558 Astable Operation (Oscillator) RL T TR CV 0 R1 RL T R2 INCREASE FREQUENCY C1 TR CV 0 C2 OUTPUT c. 558 Variable Frequency Oscillator with Fixed Duty Cycle SL00994 Figure 5. VCC R1 T C1 RL T C1 R1 RL T C1 R1 RL T C2 R1 RL TRIGGER OUTPUT 1 OUTPUT 2 TRIGGER TR 0 TR 0 TR 0 TR 0 OUTPUT 4 OUTPUT 3 TDELA TOUTPUT OUTPUT 1 OUTPUT 2 NOT USED OUTPUT 3 OUTPUT 4 Y TDELAY 3(R.C.) TOUTPUT )R.C.) SL00995 Figure 6. 558 Long Time Delay December 1988 4 Philips Semiconductors Application note www..com NE558 applications AN171 VCC R1 RL 2 5 3 TRIG 01 13 TIME 1 6 TRIG 02 13 10K C1 7 TIME 8 11 TRIG 03 13 13 R1 RL C1 10 TIME 9 14 TRIG 04 12 R1 RL C1 15 TIME 16 R1 RL C1 START RESET a. Ring Counter VCC START RESET 01 T = RC 02 03 04 b. Expected Waveforms Figure 7. SL00996 VCC = 15V C2 0.01F R1 12.5K C1 TIME RL 12.5K A single section of the quad time may be used as a non-precision oscillator. The values given are for oscillation at about 400Hz. T1 R1C1 and T2 2.25 R2C2 for VCC of 15V. The frequency of oscillation is subject to the changes in VCC. 0.1F TRIG 01 RESET R2 SL00997 Figure 8. NE558 400Hz Square Wave Oscillator December 1988 5 |
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