IC CD4538BC
The CD4538BC is a dual, precision monostable multivibrator with independent trigger and reset controls. The device is retriggerable and resettable, and the control inputs are internally latched. Two trigger inputs are provided to allow either rising or falling edge triggering.
The reset inputs are active LOW and prevent triggering while active. Precise
control of output pulse-width has been achieved using linear CMOS techniques. The pulse duration and accuracy are determined by external components RX and CX.
The device does not allow the timing capacitor to discharge through the timing pin on power-down condition. For this reason, no external protection resistor is required in series with the timing pin. Input protection from static discharge is provided on all pins.
The CD4538BC is retriggered if a valid trigger occurs followed by another valid trigger(4) before the Q output has returned to the quiescent (zero) state. Any retrigger, after the timing node voltage at pin 2 or 14 has begun to rise from VREF1, but has not yet reached VREF2, will cause an increase in output pulse width T. When a valid retrigger is initiated(4), the voltage at T2 will again drop to VREF1 before progressing along the RC charging curve toward VDD. The Q output will remain high until time T, after the last valid
retrigger.