A Dialysis Machine is an artificial kidney that treats the blood or persons with inadequate kidney function. Dialysis Machines are processor based pieces of equipment incorporating electromechanically controlled extracorporeal blood paths that leverage pumps and semi permeable dialyzer membranes to filter the patient’s blood. From an operational perspective, dialysis equipment need to meet specific safety criteria, one of which is single-fault tolerance. This means that no single point of failure in the pumps, motors, tubes, or electronics will endanger the patient or expose them to a hazardous condition. This means that there will be several redundant components and circuits, as well as "watchdog" managed disengage mechanisms in the system. These devices may include both active and passive components such as Control devices, sensors, motors, heaters, pumps, and valve drivers. Often a "Safe Mode" of operation would mean disabling the Arterial blood pump and clamping the venous line to prevent unsafe blood from flowing to the patient.
Typical Electronic Circuits in the Dialysis Machine could be:
- Sensor Control Board: Contains Analog to Digital Converters, precision references, Clocks and VCOs as well as instrumentation or operation amplifiers. Although these circuits need to respond quickly, the devices included here are often geared more towards precision than what is considered high speed today. Part of that is also driven by the need to verify a measurement or alarm signal and coordinating the response across the entire system, versus just reacting to random stimuli. The A/Ds used here would provide high reliability, good noise immunity (note that there are motors and pumps in the system), and good precision.
- Arterial And Venous Control Card: These portions of a system may include functions like; Arterial and Venous Pressure Sensors, Blood Pumps, Line Clamps, Level Sensors, blood detection Sensors, and various other monitoring and control features. Since TI's C2xxx DSPs are targeted at Motor drive and Industrial Sensor applications, they are ideally suited as the microcontroller for these blocks. Providing not only the drive and diagnostic capabilities, but also allowing the implementation of RPM, and motor coil current sensing, as well as reading the pressure transducers. There can also support the redundancy required in the system at a minimal cost impact.
- Motor/Pump Drivers: There are a number of motors, pumps, valves and heaters in a Dialysis machine. Each may need a specific drive circuit, where as some may be able to be driven directly for a C2xxx controller. Selecting the right D/A converter and drive amplifier is important to the control of the motor/pump, as well as to the life expectancy of the motor/pump. Driving any of the values or motors to hard, with signals that are to noisy can cause them to run hot and degrade quickly, as well as impact the overall comfort of the patient connected to the machine.
From TI's C2xxx family of high performance 32-Bit Controllers, through its Precisions Analog offering of Amplifiers and Data Converters, to a broad range of power management solutions, the right components with the right support are available from TI.
Application notes & user guides
Application Notes (4)