I'm trying to design a purely resistive load that is digitally controlled. The idea is of an array of resistors that are driven with power MOSFET's. I want to feed a current pattern into the microcontroller and for the load array to follow it.
It is a resistive array to provide different levels of current load. Every Resistor is switched on and OFF with a power MOSFET. The whole is going to be used to test a voltage regulator. The applied Voltage is 5V and the current is up to 1 A.
To obtain a specific Current Value the corresponding Resistors has to be switched on.
As an Example to get a current of 600 mA , the resistances delivering 100 mA (R= 50Ohm) and 500 mA (R= 10Ohm) will be on, the rest will be off. I'm planning 16 resistors. The switching between load steps has to be smooth and occur under 2µs. My concern is the transition process between two load steps.
Example : switch between step1 (R1= ON,R4=ON, rest OFF) and step 2 (R3=ON, R10=ON, R11=ON, rest OFF)
The state of the corresponding switching transistors is saved in a register and will be latched simultanaeously for all transistors. I'm using IRLML0040TRPbF (Datasheet)
The controlling microcontroller is an XMC1100.
I don't want to programm intermediary steps for the transition to be able to hold the timing criteria of 2µs.
I thought, as I don't have an inductive load, I don't need extra circuitry to assure the smootheness of the current step transistion.
am I right in that line of thought? will the current flowing in the resistors during the transition disturb the smootheness of the transistion significantly, even if I latch (from the µcontroller) simultaneously and the transistor is quite fast?
Do you guys have an idea how to proceed in that case?
I'm quite the beginner and would be grateful for any help.