AN841 Datasheet, PDF (1/4 Pages) Silicon Laboratories – THE MICROCC—A MICROAMP-RANGE CONSTANT-CURRENT SOURCE

AN841
THE MICROCC—A MICROAMP-RANGE CONSTANT-CURRENT SOURCE
1. Introduction
The MicroCC uses the TSM6025 voltage reference, a drop-in replacement for the MAX6025, with better than
15ppm/ºC stability. This is an ideal part to use both as the reference voltage and regulator for the TS1001IJ5
(previously covered here) powered by a single CR2032 coin cell. A 20- or 25-turn 10k trimmer pot serves as the
adjustment. Using 0.1% resistors at the load allows confident current measurements in the micro amp range to be
taken with any volt meter capable of 1mV resolution. A printed circuit board layout of the MicroCC is illustrated in
Figure 1.
Figure 1. MicroCC PCB Layout
As shown in Figure 2, the MicroCC uses the TS1001IJ5 in a modified voltage follower mode where the feedback is
taken from the emitter side of transistor T1 instead of the output of the op-amp, easily translating voltage regulation
to current regulation. This is by no means a new type of circuit; however, it demonstrates that a simple circuit is
capable of operating in ranges usually reserved for more complex and more expensive circuits.
Rev. 1.0 1/15
Copyright © 2015 by Silicon Laboratories
AN841