Hi all, I have just purchased the VNH2SP30 Motor Driver Carrier MD01B and have interfaced it to a microcontroller board I have based on an atmel M128. The motor drives ok but the problem I am having is that the VNH2SP30 is running very hot at 2A and the CS output is at approx 1.3 Volts which according to the data sheet is approx 10A. I Know this is not the case as I am running off a power supply which has an amperage display. I am running the system at 13.5 volts and a PWM frequency of 16KHz. Any feedback on this matter would be greatly appreciated.
Is there good reason to trust the reading on your display? Is it capable of outputting 10A? The 10A CS reading and the driver getting hot are consistent with quite a bit of power, and it’s relatively unlikely for CS to be wrong that way. Can you do some calculations from your load to figure out what the current should be?
If the power supply can only output about 2A or some other number well below what your motor is drawing, it’s possible that the motor driver supply is constantly going in and out of the valid input voltage, which could be pretty bad for the driver (and could explain it getting hot). Do you have an oscilloscope available to look at what your input voltage looks like?
One other test: what does the current draw on the power supply look like with no load or a very minimal load on the motor driver?
Hi Jan, thanks for the reply.
I agree, the CS reading and heat of the chip do indicate it is drawing 10A.
I have checked the power supply current reading and it is correct, approx 2A.
The power supply is capable of a 5A output.
I have a 4 channel DSO and have checked the waveforms and all looks good.
I have also ran the motor with a h-bridge i designed and there is no heat generated.
The no load current is in the order of mA.
Can you vary the duty cycle and see if all the readings you get vary linearly with that? If they do, and the chip isn’t getting so hot it’s overheating, you might not really need to do anything. If there is some anomaly in the readings around some duty cycle, that might give us more hints.
Finally had some time to do some more tests.
Changed the pwm frequency from 16KHz to 2.5KHz and had the same results.
So pwm frequency is back to 16KHz.
Ran the duty cycle at 100% and all is perfect. Current reads correctly and agrees with the power supply current reading. Chip does not get hot. If I run anything less than 100% duty cycle the CS pin reads high and the chip gets hot even though the motor is drawing less than 0.5A.
If the problem only shows up when switching, the problem might have to do with your wiring. What do your power connections look like? Can you post a picture of your setup?
Hi Jan, I believe you are totally correct. Am thinking that because i have wired the motor drive board from a current board I have designed that the interconnecting wires are to long and therefore causing the problem I am seeing while switching. I ran the motor drive board today at full speed at a current draw of 8 amps and all worked perfectly with hardly any heat generated. Thanks so much for your help. Greatly appreciated. Was thinking about using the board for a 24V DC application. I noted on the chip specs that the max Vcc is 41 volts. So I assume if i use some transient suppression that it should be no problem to run at 24V. What is your experience with this ?
Thanks and regards Paul
The VNH2SP30 has over-voltage cutoff that can kick in as low as 16V, so this is absolutely not a 24V driver (the 41V spec just means it won’t die). For 24V applications with more than a few amps, the best option we can offer is our discrete high-power motor driver.
We’ll have another version of that, the 24v12, up shortly (maybe today). That unit has 40V MOSFETs and it can do similar current to the VNH2SP30 while operating from a 24V battery. These discrete motor drivers don’t have current sensing built-in, so you’ll need to get that separately if you need it in your application.