Supply original CD74AC646M, Logic - Buffers, Drivers, Receivers, Transceivers, by Texas Instruments

The CD4541BC Programmable Timer is designed with a 16-stage binary counter, an integrated oscillator for use with an external capacitor and two resistors, output control logic, and a special power-on reset circuit.
The special fea tures of the power-on reset circuit are first, no additional static power consumption and second, the part functions across the full voltage range (3V–15V) whether power-on reset is enabled or disabled.Timing and the counter are initialized by turning on power, if the power-on reset is enabled. When the power is already on, an external reset pulse will also initialize the timing and counter. After either reset is accomplished, the oscillator frequency is determined by the external RC net work.
The 16-stage counter divides the oscillator frequency by any of 4 digitally controlled division ratios.
Features
• Available division ratios 28, 210, 213, or 216
• Increments on positive edge clock transitions
• Built-in low power RC oscillator (±2% accuracy over temperature range and ±10% supply and ±3% over pro cessing @ < 10 kHz)
• Oscillator frequency range ≈ DC to 100 kHz
• Oscillator may be bypassed if external clock is available (apply external clock to pin 3)
• Automatic reset initializes all counters when power turns on
• External master reset totally independent of automatic reset operation
• Operates at 2n frequency divider or single transition timer
• Q/Q select provides output logic level flexibility
• Reset (auto or master) disables oscillator during reset ting to provide no active power dissipation
• Clock conditioning circuit permits operation with very slow clock rise and fall times
• Wide supply voltage range—3.0V to 15V
• High noise immunity—0.45 VDD (typ.)
• 5V–10V–15V parameter ratings
• Symmetrical output characteristics
• Maximum input leakage 1 µA at 15V over full tempera ture range
• High output drive (pin 8) min. one TTL load