Lg. Fasoli et al., A GENERAL CIRCUIT FOR RESISTIVE BRIDGE SENSORS WITH BITSTREAM OUTPUT, IEEE transactions on instrumentation and measurement, 46(4), 1997, pp. 954-960
A low-offset integrated circuit useful for the readout of the signal c
oming from various types of integrated resistive bridge sensors has be
en developed in standard bipolar technology, The circuit, using a firs
t order Sigma-Delta A/D converter, pro,ides a clock-synchronous pulse
rate output which is highly suitable for the communication with a micr
oprocessor and for a bus environment. An almost perfect offset cancell
ation is achieved by chopping the bridge voltage supply, The simplicit
y of the circuit makes it ideal for the integration with the sensors i
tself, while the digital interference rejection allows the integration
of the digital control circuits for the bus on the same chip, The exp
erimental results show that with a clock frequency of 200 kHz a resolu
tion of 12 bits is obtained with a conversion time of 20 ms, The remai
ning offset is +/-5 mu V. The bridge imbalance can be up to 18 mV/V. D
epending on the chosen resolution the input signal bandwidth could be
from about 25 Hz (12 bits) up to 400 Hz (8 bits).