This paper describes a mixed signal integrated circuit for
current measurement. Fabricated on a 1 pm CMOS process,
the IC employs a delta sigma analog to digital converter to
generate a pulse-width modulated (PWM) output
proportional to current. A metal loop stamped into the lead
frame acts as a current sense resistor, providing a 5mV full
scale signal at 1 amp sense current. The IC measures the
sense voltage, corrects for the temperature coefficient in the
metal loop, and creates a 9 bit accurate PWM output. This
circuit consumes less than 120pA in operating mode and
less than 3pA in sleep mode.