Analog Devices,inc.

Michael G Curtin

Michael Byrne

Donal P Geraghty

An integrated-circuit (IC) chip formed with a D-to-A converter (DAC) and an amplifier to receive the DAC output and to produce a corresponding signal for an output terminal. The chip includes control circuitry to prevent harmful instability in the signal at the output terminal during times that one or more power supply voltages are changing. The control circuitry includes a voltage-monitoring device which produces a RESET signal when a monitored supply voltage is beyond its nominal operating range. The RESET signal de-activates the amplifier input and output circuits, and following a short time delay after the start of RESET, disables the amplifier by killing the amplifier bias currents. The chip is arranged to receive a RESET signal from external devices, and to produce a RESET signal for any other devices in the system.

D/A converter with improved means to prevent output signal instability

A D/A converter of the type provided with an amplifier to produce the analog output signal and formed as an IC chip. The chip includes a power voltage monitor to sense when the applied DC voltage is above a preset lower level and below a preset upper level. When that condition is sensed, the monitor activates a control circuit which in turn opens a transmission gate between the amplifier output circuit and the converter output terminal, and closes a transmission gate between the output terminal and ground. When the DC voltage goes above the preset upper level, and a valid digital word is loaded into the converter register and presented for conversion, the condition of the transmission gates is reversed to provide for normal operation of the converter.

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Limerick, Ireland

Michael G Curtin