NE555/SA555/NA555 PRECISION TIMERS Description Pin Assignments These devices are precision timing circuits capable of (Top View) producing accurate time delays or oscillation. In the time- delay or monostable mode of operation, the timed interval is GND V controlled by a single external resistor and capacitor network. CC In the astable mode of operation, the frequency and duty TRIG DISCH cycle can be controlled independently with two external resistors and a single external capacitor. OUT THRES The threshold and trigger levels normally are two-thirds and RESET CONT one-third, respectively, of V . These levels can be altered CC by use of the control-voltage terminal. When the trigger input SO-8 falls below the trigger level, the flip-flop is set, and the output goes high. If the trigger input is above the trigger level and the threshold input is above the threshold level, the flip-flop is reset and the output is low. The reset (RESET) input can override all other inputs and can be used to initiate a new timing cycle. When RESET goes low, the flip-flop is reset, and the output goes low. When the output is low, a low- impedance path is provided between discharge (DISCH) and ground. The output circuit is capable of sinking or sourcing current up to 200mA. Operation is specified for supplies of 5V to 15V. With a 5-V supply, output levels are compatible with TTL inputs. Features Timing from microseconds to hours Astable or monostable operation Adjustable duty cycle TTL compatible output can source or sink up to 200mA Green Molding Compound (No Br, Sb) Lead Free Finish/ RoHS Compliant (Note 1) Notes: 1. EU Directive 2002/95/EC (RoHS). All applicable RoHS exemptions applied. Please visit our website at NE555/SA555/NA555 PRECISION TIMERS Pin Descriptions Pin Name Pin Number Description GND 1 Ground TRIG 2 Trigger set 1/3V CC OUT 3 Timer output RESET 4 Reset active low CONT 5 External adjustment of internal threshold and trigger voltages Threshold set to 2/3 V THRES 6 CC DISCH 7 Low impedance discharge path V 8 Chip supply voltage CC Functional Block Diagram RESET can override TRIG, which can override THRESH Functional Table Nominal Trigger Threshold Discharge Pin Name Output Voltage Voltage Switch GND Irrelevant Irrelevant Low On TRIG <1/3V Irrelevant High Off CC OUT <1/3V <2/3V Low On CC CC RESET <1/3V <2/3V As previously established CC CC 2 of 14 February 2012 NE555/SA555/NA555 Diodes Incorporated www.diodes.com Document number: DS35112 Rev. 4 - 2 NEW PRODUCT