Other Parts Discussed in Thread: MSP430FR2355
Hello support team.
I have a problem when using a DC / DC converter module LMZM23600.
As shown in the schematic diagram in figure 1, I am converting the battery power to have 12 volts at the output.
With this 12-volt voltage, I generate the power for an MSP430FR2355 by a linear regulator, the LDL212PV33 and also a MAX14870 motor driver.
I did not include the MSP430FR2355 in figure 1, in order to simplify and think that it would not affect the understanding.
The MSP430 generates a PWM signal for the MAX14870 to drive a small Pololu 3057 motor running without load.
As shown in figure 2, the problem occurs, channel 0 (yellow line) shows the signal on the PWM pin and channel 1 (green line) shows the voltage 12 volts.
Channel 0 (yellow line) is on the scale of 2 volts per division and the time scale is 2 ms/div.
Channel 1 (green line) is on the scale of 5 volts per division, although the figure indicates 500 mV / div.
In figure 2 you can see that after a sudden drop, the voltage decreases until it starts to affect the supply voltage of the MSP430.
I think the voltage decreases until the LMZM23600 resumes with the soft start at around 11.5 ms.
I increased the time scale to 100 ms / div and according to figure 3, this event is repeated every ~ 480 ms.
I connected the motor directly to the 12 volt battery and measured the maximum consumption which did not exceed 70 mA.
Another test I did was to replace the MAX14870 and the motor with a resistive load (resistor + potentiometer) and I managed to reach 170 mA, I think I could go further, but the components I had limited me.
In the resistive load test, I maintained it for about half an hour and did not detect any signs of overheating that could cause failure.
As the LMZM23600 reached 170 mA with resistive load, I imagine that this problem is not due to overload.
I figured that something caused by the MAX14870 + engine might be interfering with the LMZM23600's FB pin.
I tried to place a 1N4007 diode, with the anode at the output of the LMZM23600 and the cathode at the input of the MAX14870, but it did not solve it.
By the way, I did the tests using a 12 volt, 7 Ah lead acid battery and also with two of this in series, that is, 24 volts and the results were identical.
Please, if you can give me any hint of where I'm going wrong.
Best Regards.
Figure 1
Figure 2.
Figure 3.
