How to measure power consumption

Current can be measured with the help of filters TI160808U601 and TI201209U121, which are present in all important power rails and have an internal resistance of approximately 0.3 and 0.1 Ohms respectively. The accuracy of measurements may not be as high as with resistors, but is sufficient for a rough estimate.

The filters can be replaced with 1% resistors for higher accuracy and/or dynamic values.

Power consumption measurements

=== UmTRX v2 ===

=== UmTRX v1 (for reference) ===

• Prototype 1, 03.01.2012: Powered from 8v and it takes ~ 0.5 A of static current (no fw loaded).
• Prototype 1, 14.01.2012: With FPGA bistream loaded (SRAM and Ethernet are enabled) in idle mode is approximately 6W: * Current at 6.5V was 0.89A (5.785W) * Current at 12V was 0.51A (6.12W)
• Prototype 1, 15.01.2012: Measurements : {{{
  L10-1 1.2 mv 0.3R LMS1 1.8v Analog
  L7-1 4.2 mv 0.3R LMS1 3.3v
  L9-1 1.3 mv 0.3R LMS1 1.8v Digital
  L8-1 1.8 mv 0.3R LMS1 2.5v
  L10-1 1.2 mv 0.3R LMS1 1.8v Analog
  L7-1 4.1 mv 0.3R LMS1 3.3v
  L9-1 1.3 mv 0.3R LMS1 1.8v Digital
  L8-1 1.9 mv 0.3R LMS1 2.5v
  L1 10.2 mv 0.3R 5V2 rail
  L2 2.8 mv 0.3R GPS
  L34 10.2 mv 0.08R 6.5v
  L40 0.4 mv 0.08R 3.3v FPGA
  L41 1.0 mv 0.08R 2.5v (FPGA+Clock+RF)
  L42 1.0 mv 0.08R 2.5v ETH
  L43 0.3 mv 0.08R 2.5v RAM
  L3 5.7 mv 0.3R 2.5v clock
  L47 13.2 mv 0.3R 5v RF
  L48 0.1 mv 0.3R 2.5v RF

Total: 917mW (doesn't include 1.2V FPGA core).
This is the power consumption of the system without the power conveters loss.
}}}
So you can see that from the main rails, the 6.5V one (which is the main smps rail for all subsequent linear supply) is the biggest current hog. And all that power goes mainly to the LMS and to the RF LNA. And in a smaller part to the GPS and oscillator (this is from a dummy firmware that just blinks leds, so FPGA loaded, but not doing much).

My multimeter is "only" 10.000 count and isn't good enough to measure the exact series resistance of each of these filters to get absolute values. You'd need a proper LCR to measure them I guess, but I don't have any.

• Prototype 1, 18.01.2012: measurements for idle mode ([http://code.google.com/p/umtrx/downloads/detail?name=Power_consumption_idle_18.01.2012.xls&can=2&q= xls attached here]) * Total consumption, measured at DC supply is 3.8W @ 8V. * Each LMS consumes about 1 W in idle mode. * For approx tests I suggest to use the calculated values of 0.025 Ohm for TI2012 and 0.14 Ohms for TI1608. * The efficiency DC-DC converters is more then 85%.