Power-Up Restore Circuit
Original Publication Date: 1988-May-01
Included in the Prior Art Database: 2005-Feb-15
The circuit shown in the drawing is a monostable circuit generating a pulse when the machine is starting. This allows a restore/initialization of any initial device at power on. The circuit comprises three parts: - a ramp generator (transistors 1-3)) - an inverter (transistors 4-5) - Norgate/Buffer (transistors 6-9) All nodes rise slowly following VH ramping. Node NN rises more slowly than node N1 (transistor T2 narrower and longer than T1). Thus, N1 reaches VH while NN is still ramping up. N1 high drives N2 low (T4/T5) and pulls PUP output to GND (T7) when NN is high enough to allow T3 to overdrive T2; N1 is pulled down to gnd, enabling PUP to rise. N2 is then pulled up to VH but with a sufficient delay to allow a pulse at the output.