Linear Technology Corporation

Other

Robert Essaff

Carl T Nelson

Robert C Dobkin

A drive circuit for a high-speed integrated circuit, bipolar switching regulator is disclosed. The circuit runs at megahertz frequencies, yet is efficient as previously available bipolar integrated circuit switching regulators operating at much lower frequencies. The circuitry provides three switch drive currents: a first (nominal) current that is provided while the switch is off in order to conserve power; a second (boosted) current, provided while the switch is transitioning from off to on in order to increase the speed at which the switching element switches on; and a third (drive) current, provided after the switch has turned on for maintaining the switch at a desired point in saturation. The drive current, additionally, varies as a function of the load on the switch in order, again, to conserve power. Additional circuitry increases the speed at which the switch turns off, by momentarily boosting base discharge current during the on-to-off transition period of the switch. The circuitry also increases speed by enabling the drive current prior to switch turn on. The circuitry can regulate both positive and negative outputs using a common error amplifier, as well as providing a multifunction node for shutdown and synchronization. Additionally, the circuitry provides improved recovery from output overshoot conditions. An improved clamp, to prevent the switch from spending too much time in a high power state (which would slow the switch down), increases the stability of the switch as compared with previously known designs.

High-speed switching regulator drive circuit

Synchronization and shutdown circuits and methods in high-speed

Circuits and methods are provided for increasing the turn-off switching speed of a high-speed integrated circuit, bipolar switching regulator. The regulator The circuit runs at megahertz frequencies, yet is efficient as previously available bipolar integrated circuit switching regulators operating at much lower frequencies. The increased speed switch turn-off circuitry prevents the switch from spending too much time in a high power state (which would slow the switch down), increases the stability of the switch as compared with previously known designs. In a preferred embodiment, the circuitry includes a PNP transistor and a diode-connected transistor with their base-emitter circuits coupled to form a loop with the base-emitter circuit of a NPN transistor and the base-collector circuit of the switch to limit the on state voltage of the switch and control its depth of saturation. A capacitor is connected across the diode-connected transistor to reduce instabilities due to ringing caused by delays in the feedback loop.

Circuits and methods for increasing switch turn-off speed in high-speed

Circuits and methods are provide for improving the turn-off switching speed of a high-speed integrated circuit, bipolar switching regulator. The regulator runs at megahertz frequencies, yet is efficient as previously available bipolar integrated circuit switching regulators operating at much lower frequencies. The turn-off circuitry increases the speed at which the switch turns off by momentarily providing additional current to boost the base discharge current during the on-to-off transition period of the switch. In a preferred embodiment, the circuitry includes a capacitor for storing a charge, a resistor for limiting the amount of additional current provided, and a diode for delivering the additional current to the base of an NPN transistor, the collector of which is coupled to the switch's base, for boosting that transistors collector current and the switch's base discharge current. The diode then blocks current during the off-to-on transition period of the switch. Thus, the turn-off circuitry operates on an AC basis and only when the switch is turning off.

Turn-off circuitry for a high-speed switching regulator drive circuit

A dual polarity voltage regulator circuit that is capable of regulating either positive or negative voltages is disclosed. The regulator circuitry of the present invention provides dual polarity regulation while requiring only one additional pin over a single polarity regulator. The present invention utilizes a single error amplifier, a negative feedback network, and an overshoot recovery circuit in providing dual polarity regulation. One advantage of the negative feedback network of the present invention is that the regulator circuit uses the same error amplifier (i.e., only one error amplifier) to regulate both positive and negative input voltages. The negative feedback network actively affects signals input into the error amplifier during negative regulation, but is essentially disabled during positive regulation. Thus, positive and negative voltage regulation are provided using a single error amplifier that retains its multiple functions (for example, oscillator frequency shifting, overshoot improvement and loop frequency compensation).

Dual polarity voltage regulator circuits and methods for providing

A Schottky diode structure is provided with a current collector ring surrounding the diode structure thereby collecting current injected from the diode structure which otherwise would flow into the substrate.

Schottky diode having injected current collector

A charge pump circuit is integrated form utilizes a dual emitter transistor switch having low saturation voltage. The low saturation voltage for the transistor is provided by deriving a base bias voltage from the doubled voltage (2V.sub.cc) and a collector voltage from the voltage supply (V.sub.cc). Current-limiting for the transistor is provided by connecting one emitter to the base bias circuitry whereby the second emitter acts as a collector when the transistor saturates, thereby limiting the base drive and causing current-limiting.

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Fremont, CA, United States of America

Robert Essaff