Motorola Corporation

Tim W Henry

Walter R Davis

A dual ramp analog to digital converter which employs a single supply voltage and internal logic circuitry for automatically generating automatic zero and full scale calibration voltages and a virtual second supply voltage of opposite polarity to the single supply voltage for automatically accommodating unknown opposite polarity input voltages to be measured.

Auto-polarity dual ramp analog to digital converter

A four bit binary coded decimal (BCD) up/down counter includes a four bit adder and associated logic circuitry configured to feed therethrough the incoming BCD code words as the actual output for the up count and for the down count, add binary 5 to the incoming BCD code word for 1 through 9 and invert each bit of the resulting code words, and feeding the BCD code word for zero directly to the output.

Plus five and invert algorithm

A series current steering high speed analog-to-digital converter. The converter includes means for providing n number of weighted current sources and drains of having 1/2, 1/4, 1/8, - - - 1/2.sup.n of a reference current, I.sub.r, wherein n represents an integer number, n diodes bridge circuits connected in series, n comparators coupled to corresponding bridging arms of the bridge circuits. The current sources and drains, the bridge circuits and the comparators are operatively coupled to form n sections in series to steer the currents therethrough so that the first section compares the amplitude of the input current with 1/2 of the reference current and generates the most significant bit, the second section compares the absolute valve of the difference between the input current and the 1/2 to 1/4 of the reference current for generating the second most significant bit, and so on, till the n bit digital word output is formed from the input current. Advantageously, the present series current steering analog-to-digital converter eliminates the need for sample and hold circuitry and increases the speed of the conversion by an order of magnitude compared to conventional steering circuit and can be rendered in a monolithic analog-to-digital converter structure.

Series current analog to digital converter

A current limit circuit is disclosed for sensing the current drain of a load connected in series therewith. Under normal operating conditions the circuit presents a relatively low impedance in series with the load. Circuit overload protection is provided if the current increases above a predetermined value by a current limiting circuit provided for limiting the current conducted therethrough. In response to the current limiting condition, thermal shutdown of the circuit occurs to reduce the current that is supplied to the load to a predetermined minimum value i.e., the current limit circuit presents an impedance to the load which is relatively much greater than the impedance of the current limit circuit during normal operating conditions. After a predetermined time, the current limit circuit is again rendered operative and if the circuit overload condition is still present the aforedescribed cycle is repeated until the fault condition is corrected.

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Tempe, AZ, United States of America

Tim W Henry