XL551

XD551 DIP8 XL551 SOP8 D D D D D D D Very Low Power Consumption 1 mW Typ at VDD = 5 V functional block diagram Capable of Operation in Astable Mode VDD 8 CMOS Output Capable of Swinging Rail to Rail THRES High Output-Current Capability Sink 100 mA Typ Source 10 mA Typ 6 CONT 5 R RESET 4 R1 R 3 1 OUT S R Output Fully Compatible With CMOS, TTL, and MOS TRIG 2 R Low Supply Current Reduces Spikes During Output Transitions 7 DISCH 1 GND Single-Supply Operation From 1 V to 15 V RESET can override TRIG, which can override THRES. GND TRIG OUT RESET 1 8 2 7 3 6 4 5 VDD DISCH THRES CONT description The XDXL551 is a monolithic timing circuit fabricated using LinCMOS process. The timer is fully compatible with CMOS, TTL, and MOS logic and operates at frequencies up to 2 MHz. Compared to the XL555 timer, this device uses smaller timing capacitors because of its high input impedance. As a result, more accurate time delays and oscillations are possible. Power consumption is low across the full range of power supply voltage. Like the XL555, the XDXL551 has a trigger level equal to approximately one-third of the supply voltage and athreshold level equal to approximately two-thirds of the supply voltage. These levels can be altered by use ofthe control voltage terminal (CONT). When the trigger input (TRIG) falls below the trigger level, the flip-flop isset and the output goes high. If TRIG is above the trigger level and the threshold input (THRES) is above thethreshold level, the flip-flop is reset and the output is low. The reset input (RESET) can override all other inputsand can be used to initiate a new timing cycle. If RESET is low, the flip-flop is reset and the output is low.Whenever the output is low, a low-impedance path is provided between DISCH and GND. All unused inputsshould be tied to an appropriate logic level to prevent false triggering. While the CMOS output is capable of sinking over 100 mA and sourcing over 10 mA, the XDXL551 exhibits greatlyreduced supply-current spikes during output transitions. This minimizes the need for the large decouplingcapacitors required by the XL555. The XDXL551C is characterized for operation from 0 °C to 70°C. 1 XD551 DIP8 XL551 SOP8 FUNCTION TABLE RESET VOLTAGE † TRIGGER VOLTAGE † THRESHOLD VOLTAGE † OUTPUT DISCHARGE SWITCH MAX MAX >MAX >MAX Low On >MAX >MAX