Hi guys,
I'm designing a testing device that's supposed to, among other things measure the current consumption of the DUT, preferably without switching any relays or anything. The DUT has several power modes, the extremes of these are one where it consumes around 1 Amp, the other is a deep sleep mode, where it consumes around 3uA. Both of these must be tested, to know whether or not there are any leakages, or anything fishy.
The schematic in the attachment seems ideal for this - when the current is in the upper values, the diode for the 1k shunt will activate, since the voltage on the 1k resistor would be well over ~0.6V (or 0.2ish for a schottky diode). A differential measurement would connect the shunts to an ADC with a Mux and amplifier. This would measure the voltages, check which ranges should be ignored and then choose the proper range.
This would limit the shunt power as well as giving enough resolution for all orders of magnitude that need to be tested. Also, no range switching would be involved at all.
Is there any drawback to this kind of solution?
I've only found that the limit voltage of a diode will vary over temperature, but that can be simply fixed by using a lower discrimination limit.
Thanks,
David