when measuring the load current I realise that the current goes both ways (+ and -),..
* For devices where the voltage (across it´s pins) is directly proportional (like a resistor): use RMSMy question: when designing my pass device to support maximum load current, which numbers should I use, average or RMS current? And why?
It is surprising; a small digital circuit as a load to a LDO regulator is not expected to act like this! Can you please provide more details?
This s a vague question, thus I can´t answer it.How about if I want to calculate the current consumption of a switching digital blocks, do I use RMS or AVG?
For a DC current, the average and the RMS are the same.
Not correct. This is true only for a constant current.
I guess I need not elaborate.
When I think about DC current, then it´s a straight horizontal line...
Not for pulsed DC. But that's just theory and doesn't actually matter for the question.For a DC current, the average and the RMS are the same.
Do you actually expect 200 MHz current components loading the power supply? Did you forget to install bypass capacitors in your circuit?The circuit itself is a driver circuit that is switching at 200MHz.
How about if I want to calculate the current consumption of a switching digital blocks, do I use RMS or AVG?
Basically I want to make sure that I design the size of my pass device sufficiently to support the digital circuit while it's switching at its highest frequency and heaviest activities. I have the waveform of this current (kind look like noise with peaks here and there, e.g. 5mA peak, 10mA, etc), I'm wondering if I should calculate RMS or AVG for designing the LDO's pass device.
...in most cases. It depends what you want to calculate
Hi,
This is exactly my idea, too (without more information from the OP)
Klaus
As I stated, for a steady DC output, such as from a linear regulator, the average current is the same as the RMS current (for DC the RMS calculation is trivial).LDO pass transistor power dissipation is (Vin-Vout)*avg(Iout). Additional considerations for SOA. Irms isn't present in the calculations.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?