INTEGRATED CIRCUITS AN171 NE558 applications 1988 Dec Philips Semiconductors Application note NE558 applications AN171 disabled. After reset is finished, the trigger voltage must be taken high and then low to implement triggering. 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. 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 * 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 R1 C1 RESET S1 R2 5 13 3 1 6 8 TR1 10 11 TR3 15 9 14 16 TR4 2 C2 7 C3 C4 4 CIRCUIT OPERATIONS VCC 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. R4 12 RL1 LOAD SWITCH TR2 RL2 RL3 (558) S2 (559) RL4 R3 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. 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. TEST BOARD FOR 558 OUTPUT STRUCTURE 558 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. 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. 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 NE558 applications AN171 RESET V+ V+0 R1 R4 V+0 R2 R3 2.2F C1 C3 C2 C4 SI GND LOAD V + (558) RL2 GND (559) RL3 INPUTS 1 OUTPUTS 2 1 4 3 2 4 3 a. Test Board Layout b. Foil Side SL00991 Figure 2. VCC R T R RL T C R RL T C R RL T C RL C TRIGGER T 4(RC) - 2 HRS TRIGGER TR 0 TR 0 TR 0 TR 0 OUTPUT OUTPUT SL00992 Figure 3. 558 Two-Hour Timer December 1988 3 Philips Semiconductors Application note NE558 applications AN171 TRIGGER VCC R1 RL C1 R1 RL C2 R1 RL C3 R1 T T T T TR 0 TR 0 TR 0 TR 0 CV CV CV CV TRIGGER VCC OUTPUT 2 OUTPUT 1 RL C4 OUTPUT 1 OUTPUT 2 OUTPUT 4 OUTPUT 3 OUTPUT 3 ADJ UP 50: 1 RANGE OUTPUT 4 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 0 NOTE: T = RC R1 RL R2 T TR T TR C TR 0 T 0 C1 C2 OUTPUT OUTPUT a. Monostable Operation (One-Shot) b. 558 Astable Operation (Oscillator) VCC RL R1 INCREASE FREQUENCY R2 RL T T TR TR C1 CV 0 C2 CV 0 OUTPUT c. 558 Variable Frequency Oscillator with Fixed Duty Cycle SL00994 Figure 5. VCC TRIGGER R1 RL R1 RL R1 RL R1 RL OUTPUT 1 T T C1 TRIGGER TR 0 T C1 TR 0 T C1 TR 0 C2 TR 0 OUTPUT 2 OUTPUT 4 OUTPUT 3 TDELA OUTPUT 1 OUTPUT 2 OUTPUT 3 OUTPUT 4 TOUTPUT Y TDELAY 3(R.C.) TOUTPUT )R.C.) NOT USED SL00995 Figure 6. 558 Long Time Delay December 1988 4 Philips Semiconductors Application note NE558 applications AN171 VCC R1 RL 2 5 C1 7 TIME C1 10 6 8 13 R1 RL 15 C1 TIME 11 TRIG 02 TRIG 01 RESET R1 RL TIME 1 3 START R1 RL 9 14 TRIG 03 13 13 C1 TIME 16 TRIG 04 13 12 10K a. Ring Counter VCC START RESET T = RC 01 02 03 04 b. Expected Waveforms SL00996 Figure 7. 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. VCC = 15V C2 0.01F R1 12.5K RL 12.5K C1 TIME 0.1F TRIG 01 RESET R2 SL00997 Figure 8. NE558 400Hz Square Wave Oscillator December 1988 5