U.S. Philips Corporation

Othmar Pfarrkircher

Robert Meyer

A circuit arrangement for monitoring an output load (,) of a digital-to-analog current converter (,). The digital-to-analog converter supplies an analog output current dependent on a digital comparison data word to a first resistor (,) and, if present, to the output load (,) arranged in parallel with the first resistor. In order to provide a continuous monitoring of the output load, a digital first comparator (,) compares the data words applied to the digital-to-analog current converter (,) with at least one comparison data word. An analog second comparator (,) compares the voltage drop across the first resistor with at least one reference voltage and applies its output signal to a flip-flop (,). A comparison circuit (,) monitors the magnitude and/or the presence of the output load dependent on the output signals of the first comparator and the flip-flop.

Circuit arrangement for monitoring an output load

A circuit checks the value and the existence of an external load of a digital-to-analog current converter. A first comparator compares a digital word to be converted, with a comparison data word. The output signal of the first converter indicates during which periods the digital data word is greater and during which periods it is smaller than the comparison data word. A second comparator compares the voltage at the output of the converter with a reference voltage. The output signal of the second converter indicates during which periods the output voltage is greater and during which periods it is smaller than the reference voltage. A comparison circuit checks the existence and the value of the output load by comparing the time periods indicated by the output signals of the two converters. Thus, a conclusion about the existence and the value of the output load is possible at any time.

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Hamburg, Germany

Othmar Pfarrkircher