Thermal mass flow transducer including PWM-type heater current driver

A thermal mass flow transducer includes first and second constant current sources, a first temperature sensitive element, a second temperature sensitive element, a heater element, and a control circuit. The control circuit is coupled to the heater element and is further coupled to receive temperature signals from the first and second temperature sensitive element. The control circuit is responsive to the temperature signals to determine a temperature difference between the first and second temperature sensitive elements, to generate a pulse width modulation (PWM) current based on the determined temperature difference, and to supply the current to the heater element at a current magnitude sufficient to maintain the temperature difference at a predetermined value.