Fluid ejection device with feedback circuit

A fluid ejection assembly comprising:

• a plurality of drop ejecting elements arranged in a plurality of zones, with each zone having at least one drop ejecting element, wherein the drop ejecting elements of each zone are configured to conduct electrical current between a corresponding supply voltage and a corresponding reference voltage, and wherein up to all drop ejecting elements of a group of the plurality of drop ejecting elements are enabled to conduct at a given time, with each conducting drop ejecting element of the enabled group having a corresponding drop ejecting voltage;
• a zone controller configured to provide a corresponding desired supply voltage for each zone based on a temperature level of the drop ejecting elements of the corresponding zone;
• and
• an energy controller configured to couple across each conducting drop ejecting element of the enabled group and configured to regulate the supply voltage for each zone based on selected corresponding drop ejecting voltages and on each zone's corresponding desired supply voltage,
• wherein the enabled group is successively shifted through each zone according to a selected enabling pattern in response to a start signal and a clock,
• wherein each zone includes a supply path at the corresponding supply voltage and a return path at the corresponding reference voltage with each drop ejecting element of a zone coupled between the zone's supply path and return path, and wherein each drop ejecting element of a zone is individually selectable to conduct electrical current from the supply path to the return path to cause the drop ejecting element to eject a fluid droplet, wherein the zone controller comprises:
• a zone computer configured to calculate a corresponding setpoint supply voltage for each zone based on the temperature level of the drop ejecting elements of the corresponding zone and an enable signal representative of a number of drop ejecting elements in the enabled group;
• a plurality of memories, each memory corresponding to and storing the calculated setpoint supply voltage for a corresponding one of the zones;
• and
• a plurality of digital-to-analog converters each corresponding to a different one of the memories and configured to convert the setpoint supply voltage stored therein to a corresponding desired supply voltage.

A method of operating a fluid ejection assembly having a plurality of drop ejecting elements, comprising:

• arranging the plurality of drop ejecting elements into a plurality of zones with each zone having at least one drop ejecting element, wherein the drop ejecting elements of each zone are configured to conduct electrical current between a corresponding supply voltage and a corresponding reference voltage;
• enabling a group of the plurality of drop ejecting elements to conduct electrical current for an ejection operation;
• conducting an electrical current through up to all drop ejecting elements of the enabled group, each conducting drop ejecting element having a corresponding drop ejecting voltage;
• providing a corresponding desired supply voltage for each zone based on a temperature level of the drop ejecting elements of the corresponding zone;
• and
• regulating the supply voltage for each zone based on selected corresponding drop ejecting voltages and each zone's corresponding desired supply voltage, wherein providing the corresponding desired supply voltage further comprises:
• calculating a setpoint supply voltage for each zone based on the temperature level of the drop ejecting elements of the corresponding zone and on an enable signal representative of a number of drop ejecting elements in the enabled group of drop ejecting elements;
• storing the calculated setpoint supply voltage for each zone in a corresponding one of a plurality of memories;
• and
• converting the setpoint supply voltage for each zone to the corresponding desired supply voltage.