Hi, i’m using EV6540HA Evaluation board for MP6540HA IC test.
i have a question about reference resistor value for current sensing equation on your datasheet
The equation : V_sout = V_ref + ((I_load x R_term))/9200
(I’m sorry i’m trying to upload images but the “New user can upload embedded media only…” error occured)
On the EV6540HA schematic, for phase current sensing, you have 2 resistors(value is 4.99kohm) for Vref and current sensing circuit gain(i guess).
So, my question is what is the value of R_term(on your datasheet) on your EV6540HA circuit.
what value do i have to use for converting V_sout(Gate driver ADC voltage output) to I_load value.
Iso is proportional to the Load current shown by the following image.
The SOx pins can either sink or source current proportional to this. The ratio of Iload to Iso is shown as Iso = Iload/9200. For the ratiometric output it states to have 2 equal value resistors with one going to the supply of the ADC. Ideally at 0 current the ADC would read the middle value and if Iso sources current it would rise above and increase the voltage and if it sinks current it would fall below this middle point. Our EVB has values of 4.99k for these resistors. I believe you want to choose the resistor values such that the voltage fluctuations do not lead to readings outside the adc’s measurable bounds.
i designed phase current sensing circuit like your Evaluation board with two 4.99k.
the Vref for current sensing resistor circuit is 3.3V in my circuit(same as ADC reference voltage)
Q1. In my case, Vref of Vsout equation(on your datasheet) is 1.65V, am i correct?
Q2. For converting Vsout(ADC input signal) to the Current value in software, Rterm of Vsout equation is 4.99k according to your answer, am i correct?
Q3. This is another subject, under what temperature condition is the typical current sense ratio value(in your datasheet) tested?
in your datasheet(current sense ratio vs temperature), the current sense ratio fluctuates greatly depending on temperature.
when following the example in the evb where one resistor is pulled to the 3.3V or 5V and another is to ground the following instructions apply.
Vsout value at no current would be 1.65 for 3.3V. . this will cause it to rise or fall depending on if it is sinking or sourching.
This how the typical values are reported from the datasheet
. this will cause it to rise or fall depending on if it is sinking or sourching.