Other Parts Discussed in Thread: , INA240
Hi Team,
When the coil load is driven by DRV8870 which I bought from TI Store last month, the current of load changes as shown in the following figure:
where the horizontal axis is the measuring time, the vertical axis is the load current and VM = 30V, the load is <1Ω, <1mH.
First, the current rises as expected. Then, after the current reaches the peak point, it starts to decrease slowly, which is unexpected.
I found that this phenomenon is caused by 3 reasons：
- The temperature of the load and the chip increase leading to the increase in resistance(load and chip internal RDS); It is the reason for the current drops like the latter part of the above image.
- The output of DRV8870 jitters, and its range accounts for 5% of total output signal, shown as followed. No jitter in input PWM. This is also the reason for the current drops like the former part of the above image(current from 1686mA to 1602mA).
- The high-level voltage of the output signal is always lower than VM 5~6V, e.g., Input VM = 30V, my measured output is 24V, wondering where is the 6V difference.
Note that the reason 2 and 3 are found under the measurement without load, so these reasons have nothing to do with the load.
And I want some explainations about the reason 2 and 3, that is jittered output and lower output voltage while correct input.
Thank for your help.
