Asynchronous reset and its timing implications
The CD4040BPW resets asynchronously — the counter clears to zero the instant the reset pin goes high, regardless of the clock state. This means the reset is not synchronized to the clock edge, so in a system where the counter must be cleared at a precise clock phase, an external synchronizer is required to avoid metastability at the reset release. The count advances on the negative (falling) edge of the clock input. If the driving signal is positive-edge-aligned, consider inverting the clock before feeding it to this device.
Housed in a 16-lead TSSOP (4.40 mm body width), the CD4040BPW requires a surface-mount footprint with 0.65 mm pitch. The narrow pitch limits manual rework; a hot-air station or reflow oven is recommended for soldering. Supplied in tube packaging — not tape-and-reel — so it is suited for low-to-medium volume assembly where pick-and-place feeders expect cut-tape or tube loading.