Abstract: A V.35 compliant driver is disclosed. The driver has three operational modes: OFF, low power (approximately 1/3 full power), and full power. The driver is placed in an appropriate mode based on conditions sensed at driver outputs. More particularly, the driver turns OFF upon sensing a short circuit condition, and reverts back to a normal operating condition following cessation of the short circuit condition by transitioning through a low power mode. Innovative approaches for satisfying V.35 source impedance measurement requirements and driver termination are also disclosed. All of the components associated with the driver reside on a single integrated circuit.

Abstract: A programmable charge pump produces a selected one of a plurality of bipolar output voltages in response to a pump select input signal. Transistor switches in the charge pump are controlled by logic circuitry so as to provide the selected bipolar output voltages. The charge pump may include a power management circuit to optimize power consumption by varying the clock frequency based on the current being drawn by the load. The charge pump may be fabricated as an integrated circuit which supports a plurality of interface standards requiring different bipolar supply voltages.

Abstract: A voltage tripler which uses a charge pump with a single charge transfer capacitor to produce the required voltage is disclosed. The voltage tripler in conjunction with an inverter is useful for producing voltages with negative polarities. The voltage tripler when used in conjunction with a variable frequency oscillator circuit is useful in optimizing the power consumption by the charge pump of the voltage tripler when the tripler is not operating under load conditions. The tripler is useful in supplying power to a combination RS232 and RS422 or RS232 and RS485 interface, as well as other monolithic interface products.

Abstract: Charge pump circuitry is implemented using a voltage shifting technique to generate a symmetrical bipolar voltage. The symmetrical bipolar voltage charge pump power supply can be fabricated as an integrated circuit on a single substrate, and can be integrated with various interface circuits to provide symmetrical bipolar voltage thereto. The charge pump includes voltage shifting circuitry which generates an increased output voltage of a negative polarity and an increased output voltage of a positive polarity. The shifting circuitry is responsive to an internal oscillator which triggers charge accumulation and voltage shifting. Neither output voltage is generated from the other output voltage. Rather, the negative and positive supply voltages are each generated, in substantially the same manner, by charge transfer effected by the voltage shifting circuitry in response to triggering by the internal oscillator.