POWER SUPPLY THRESHOLD ACTIVATION CIRCUIT

• Main Authors: HOUK, WILLIAM R, RAO, HAYAGRIVA V
• Format: Patent
• Language: English; French
• Published: 11.03.1986
• Edition: 4
• Subjects: BASIC ELECTRONIC CIRCUITRY; CALCULATING; COMPUTING; COUNTING; ELECTRIC DIGITAL DATA PROCESSING; ELECTRICITY; PHYSICS; PULSE TECHNIQUE

Title of the Invention POWER SUPPLY THERESHOLD ACTIVATION CIRCUIT An improved tristate enable circuit is described for activating a tristate enable gate to maintain the high impedance third state of a common bus tristate output device during "power down" and "power up" transitions of the common power supply Vcc. The enable gate circuit element tends to turn off at a voltage level Vcc2 generally greater than the voltage level Vcc3 at which the tristate output device circuit elements turn off. As a result the high impedance state may be lost during "power down". A threshold activation circuit is coupled to the enable gate for activating the enable gate when the threshold activation circuit senses a higher common power supply voltage level Vcc1. The threshold activation circuit operatively activates the enable gate over a voltage range from Vcc1 to a lesser common power supply voltage level Vcc4. Component values are selected for relating the voltage levels so that Vcc1 > Vcc2 and Vcc3 > Vcc4. As a result the turn off or circuit elements is sequenced by the threshold activation circuit.