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Too much current when duty cycling

Question asked by Yanodamano on Feb 9, 2015
Latest reply on Feb 9, 2015 by Achim

We have an ultra low current battery (3V) powered design that has a full bridge strain gauge (10K). We use an AD8237 configured with a gain of 500 and some offset. In order to save power we duty cycle the whole circuit (amp and bridge power) at 20% using a high sided FET 5ms with 1000us (we hope to reduce this with a lower gain) on time for settling. The strange thing is the current consumption when on is not much different to the current when duty cycled? Does anyone know if I can duty cycle this part? Could the switch on current of the AD8237 be so high it negates the theoretical 80% saving of the duty cycle? Could it be the high side switching transients or the switching on of the bridge power (sudden signal change) that is drawing the extra current? Would the AD8235 with its shutdown be a better choice or would it do just the same? Thanks 

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