A while ago I needed some small value resistors as current shunts and I started wondering about the feasibility of using traces as resistors.
There are many theoretical reasons as to why copper traces make bad shunt resistors, but I found surprisingly little practical data.
The traces are (from left to right):
- 20 mil wide, 1221 mil long, should be ~30mOhms
- 6 mil wide, 611 mil long, ~50mOhms
- 12 mil wide 1221 mil long, 50 mOhms
- 6 mil wide 1221 mil long, 100 mOhms
Using traces as resistors - [Link]
Here is a PDF document from Linear Technology, featuring current sense circuits for different applications, including High side, low side, level shifting, high and low voltage, fault sensing, etc: [via]
Sensing and/or controlling current flow is a fundamental requirement in many electronics systems, and the techniques to do so are as diverse as the applications them-selves. This Application Note compiles solutions to current sensing problems and organizes the solutions by general application type. These circuits have been culled from a variety of Linear Technology documents.
Current sense circuit collection - [Link]
20 Amps DC Ammeter using very low value resistance of 0.01 Ω
- Supply voltage. symmetric power (+ -12)
- Maximum current measure. 20A
- With Possibility of increasing the measurement range
- Resolution 10mA
20 Amps DC Ammeter - [Link]
The TL431 is a three-terminal adjustable shunt regulators, with specified thermal stability over applicable automotive, commercial, and military temperature ranges. The output voltage can be set to any value between Vref (approximately 2.5 V) and 36 V, with two external resistors.
- Operation from -40°C to 125°C
- Reference voltage tolerance at 25°C
- 1%: A grade
- 2%: standard grade
- Low output noise
- 0.2-Ω typical output impedance
- Sink-current capability: 1 mA to 100 mA
- Adjustable output voltage: Vref to 36 V
TL431: Cost-effective shunt regulator solution - [Link]