| 摘要 |
An analog subsystem is disclosed which can be included in a single monolithic, integrated circuit chip and which is for use with a digital subsystem to form a dual ramp analog-to-digital converter. A current steering network included in the analog subsystem is connected to a reference current source and to an input voltage-to-current converter. An integrator is connected to the output of the current steering network, and a comparator is connected to the output of the integrator. The current steering network selectively conducts the current from the converter to charge the integrator for a predetermined period of time, which is terminated by the application of a signal to the current steering network by the digital subsystem. The network then conducts the current from the constant reference current source to discharge the integrator which ultimately triggers the comparator. A comparator output signal then terminates the count of a counter in the digital subsystem to provide a reading proportional to the magnitude of the analog voltage being measured. The analog subsystem further includes a ramp offset current source which increases system noise immunity and improves the linearity of the current steering network. Temperature compensating, tracking, and limiting techniques are utilized to decrease the effect of temperature on the analog subsystem and to increase speed of operation.
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