One of the many challenges for silicon manufacturers, specifically in the industrial and medical applications market segment, is to address the designers’ need for interfacing resistive transducers to a signal conditioner over a variety of input configurations. Manufacturers must be able to do this with minimal requirements for external circuitry, while providing multiples options for digital and analog outputs.
Resistive transducers can provide weight, temperature, pressure, flow and level measurements; these transducers, converting a physical quantity into an electrical signal, function the best when supplied with the proper voltage or current source. The transducer supply driver must also enable configuration flexibility to provide the application designer with an optimal range of choices in the product development phase.
In addition to accommodating various sensing element types, sensor signal conditioners are required to provide the processed input signal in a variety of output options: either digital or analog and either voltage or current.
Renesas developed the ZSSC3240 sensor signal conditioner based on decades of experience helping sensor module designers meet these challenges.
The following diagrams each illustrate a specific, but typical input configuration, highlighting the analog front end (AFE) flexibility. The external temperature sensor connections are shown on the left side of the pictures, with the main sensor connections on the right.
Tracks in blue identify sensors supply lines, and tracks in red indicate the signal inputs to the analog conditioning chain.
This shows a separate diode / PTC resistor as a temperature sensor supplied by a programmable current source, and main sensor element (bridge) supplied through a ratiometric voltage source.
A bridge is used as a temperature sensor when supplied by a programmable current source with an internal programmable resistor (Rt).
The ZSSC3240 analog front end is also equipped with sensor diagnostic features to ensure trusted system operation in the presence of faults. These diagnostic checks can also be included in the cyclic measurement stream offered by the configurable scheduler integrated in the signal conditioner.
The ZSSC3240 output can be either digital (SPI, I2C, OWI) or analog (0-1V, 0-5V, VDD ratiometric). A 4-20mA current output and One Wire Interface (OWI) over current loop further expand the options for connectivity provided to the system designer.
Voltage output, digital (SPI or I2C) and analog (absolute voltage 0-1V or 0-5V)
Current loop 4-20mA with OWI over current loop
Additional versatility is enabled by the ZSSC3240 SSCs’ capability to control an external FET, allowing the supply to be as high as 48V and to operate directly from the voltage level provided by a current loop.
The ZSSC3240 provides a wide range of options for the configuration of the input transducer interface to the analog signal conditioning chain; also, the multiple choices for the selection of the SSC output type are addressing a variety of needs for interfacing the signal conditioner with the next stage of information processing.
With the above features, the ZSSC3240 offers the designer a wealth of flexible tools to overcome next product generation design challenges.