Part Number: DRV8711
Hi All,
There's no tolerance given on the DRV8711 datasheet for ISGAIN. Can anyone comment on what min/max values and tempco might be expected.
Hi Anders,
There is no problem in the graph of Rdson vs. Temperature in the datasheet.
There are two formula shown in the datasheet, they are used to caluculate the maximum ambient temperature. Let's take 4A output current as an example. From the graph of Rdson vs. Temperature in the datasheet, we know Rdson~=77mOhm with Tj=135 degC. We use Tj=135 degC here, because the OT trip point is 150°C with ±15°C tolerance.Then Pdiss~=1.232W, and the power dissipated in the packge is around 2.5W (H-bridge). Note that this number is only the heat loss on Rdson, not including the loss on the bonding wires, the loss on the package lead and so on. Then Ta=135-(22*2.5)=80 degC. If counting the other power loss in the package, the maximum ambient temperature should be a little lower.
Best regards,
Shawn Zheng
Hi Rick-san,
Thank you for the explanation.
Regarding your answer, I understood as follows. Please confirm whether my recognition is correct.
- To guarantee DRV8830 to communicate correctly, the device input requires below voltage.
- High input : Must be higher than 0.5 x VCC. (i.e. when VCC=6V, input must be higher than 3.0V to guarantee operation.)
- Low input : Must be lower than 0.25 x VCC.(i.e. when VCC=6V, input must be lower than 1.5V to guarantee operation.)
It seems the datasheet description is not a general way to specify the VIL/VIH spec. It is very confusing. I believe that normally, VIL spec has TYP/MAX value and VIH has MIN/TYP value specified.
Or, it is easier for me to understand if the parameter is "Input High Voltage Threshold" instead of "Input High Voltage"
Best Regards,
Kawai
Hi Kawai-san,
- High input : Must be higher than 0.5 x VCC. (i.e. when VCC=6V, input must be higher than 3.0V to guarantee operation.)
- Low input : Must be lower than 0.25 x VCC. (i.e. when VCC=6V, input must be lower than 1.5V to guarantee operation.)
Your statements above are correct.
Thank you for your comments. We will add this to the list of future datasheet updates to remove this confusion.
Hi Mathew,
Yes, please do, the title of this thread could be misleading to the new content. Thank you very much.
Part Number: DRV8701
Hi,
I have a product that is to use the DRV8701E for many different applications and different motor ratings. I have a fixed sense resistor of 0.005 Ohms that I calculated for the maximum Ichop of 50 A.
Ichop = (Vref-Voff) / (Av x Rsense) assuming I want a 50A max, 5V microcontroller, Av is 20 and Voff is about 10mV, I find that Rsense is 0.005 Ω (@ 5 Watts).
I have 3 different motors I’m using this design on @ 31 Volts (Bridge rectified AC), with a software adjustable Vref.
So I was under the assumption I could use the Vref to limit the maximum current of the motor and prevent damage to the MOSFETs.
I made a table and graph of all the different software to voltage values that I’ve included with this data.
If I use the 588W Motor @ 31V I should expect a max current of 18.9A. This gives me a Vref of 1.91 & a PWM setting of 96/255. This motor runs fine and has a slight increase as it should. The 115 watt motor runs fine as well when set to the correct Vref.
The problem is the 160 Watt Motor I’m using should have a Vref of 0.54 V. This gives me a PWM setting of 26/255. The motor is in a screw drive reducer but fails to run, being limited at this value of Vref. Even if I set Vref to 96/255 like the large motor it still fails to run. If I set it around 150/255 ~ 3 volts I can just get it to run!
So what I’m gathering is that Vref doesn’t seem to be an Average current cutoff but it’s only an instantaneous value, is this correct? This makes me afraid of the 588 W motor under load as well (but it will draw 10A with the correct Vref Setting)
Any additional information you would like I will happily provide.
Thank you,
Mat
Hi Rick,
This does appear to be the case for the output voltage as expected. So I get that the Vref is cutting it off, but why would the instantaneous current be so high? I understand that if you look at the time it takes for a MOSFET to go from 0V-30V there is a small period of extremely high current, but I'm not sure why this would affect this motor and not the one that's over triple it's size!
Thank you,
Mat
Seil,
Please excuse me for delayed response.
May I know where is the option to disable close loop current ? I checked the GUI and did not find
any. Please let me know.
Cheers,
Jayant Arora
Sent from my iPad