APPLICATION SPECIFIC INTEGRATED CIRCUIT FOR PHYSIOLOGICAL MONITORING

An application specific integrated circuit (ASIC) for physiological monitoring that has multiple inputs and outputs for flexible system architecture in which multiple ASICs are easily coupled together to expand the number of channels being monitored. Each ASIC has multiple inputs that may be coupled to the patient and analog expansion inputs to accept signals from other ASICs. A buffered version of the patient inputs allows signals to be transferred to other ASICs. A lead summing network, under control of lead select and system configuration lines, sums the patient inputs, the expansion inputs, or both, to produce various signal leads. Multiple ASICs are easily coupled together to produce any number of signal lead combinations. In one embodiment, the ASIC is used for ECG monitoring and has inputs coupled to patient electrodes and buffered versions of each patient input. The ASIC also has expansion inputs to accept signals from other ASICs. A single ASIC can operate in a standard mode for three-lead or five-lead operation or in the Holter monitor mode. The ASIC also has pacer detection circuitry to detect standard pacer pulses and bioimpedance pulses even in the presence of respiration monitoring signals. The system can be expanded using two ASICs for twelve-lead ECG monitoring or three ASICs for fifteen-lead monitoring. The ASIC also includes circuitry for lead drive and lead fault detection, pacer delay, blanking, trace recovery circuit, programmable bandpass filters, programmable gain amplifiers, an analog multiplexor and sample/hold circuit to allow easy interface to an external analog to digital convertor.