DRV8304: VGHC is not high enough to drive the Mosfet correctly.

Nikos,

Can you try a second IC? Maybe this first one got damaged during debug.

Regards,

-Adam

hi,

I dont have anymore a new one, that was the third IC that I used. Now I have the same problem at the VGHB and I did not something special, I use a micro-controller to program the DRV3804 with SPI and  a multi-meter or oscilloscope to check the voltages. 

I would like to now if there is from your experience something special to cause this problem, because if I buy a new one and goes damaged again I spend my time without a better result. 

Maybe the Mosfets cannot work with drv? Maybe the IDRIVEN and IDRIVEP is not correct and the drv8304 goes defect? Can this parameters damage the drv8304?

I am using the sira80dp Mosfets with this parameters:

and the IDRIVEP = 15mA and IDRIVEN = 30mA for both of the H and L Mosfets.

I made also now some measurements, the RDSon of the Low Side Mosfet is ca. Zero Ohm and the high side Mosfets have an RDSon about 4 Kohm.

I have changed the TDRIVE Time and I saw that if the values is 500nS then the High Side Mosfet does not goes on, if the TDRIVE is 4000 ns then the high Side Mosfet has 4 kOhm RDSon.

The Bridge A seems to work properly, that means I have VGHA 20 Volt with VM 11 Volt but also the High Side Mosfet has RDSon 80 Ohms, that is also too much. The Low side Mosfet has ca. zero Ohm RDSon like the other bridges.

Everything is very strange to me.

King Regards,

Nikos

Hi,

I changed the PWM mode to 1X and then was again the VGS-H 20 Volts and I changed back to 3XMode and the VGS-H was again 10 volt. What means this? Is drv damaged?

The Low Mosfets are turn on but the high side mosfets cannot turn on, I wrote it also in my previous post. The VGS-H in 1x Mode is 20 Volt but Mosfet does not turns on.

I calculate the IDRIVEP and IDRIVEP like the equation in datasheet:

Idrivep> Qgd/tr and Idriven>Qgd/tf, my mosfet has tr = 23 ns to 50 ns and Qgd 12,3 nC so IDRIVEP is ca. 0,53mA to 0,246 mA the DRV8304 has a minimum of 15 mA. What is it means? Maybe I cannot use this mosfet with DRV8304? Is the Mosfets or drv8304 damaged?

I use 15mA/30mA for the IDRIVEP/N

Nikos,

Typically we suggest 100-200nS VDS rise time. Using the value for Qgd from the FET datasheet and the same formula you used I calculate that you need between 60 and 120mA to drive these FETs effectively.

The DRV8304 should have no issue driving these.

Can you show us a scope plot of the FET gate to source differentially so we can see when and why the gates aren't turning on?

Regards,

-Adam

Hi,

I have the following troubles with my PCB construction.

First I set the DRV8304 to 3XMode and I try to drive the B Half Bridge, The measurements are according to ground. VM is ca. 12 volt.

This is VGLB, it seems to working correctly.

This is VGHB according to ground, according to source I have a straight line and the Mosfet does not turn on. It seems to have big issues.

Now I change the DRV8304 to 1xPWM Mode and I use the following code to change every 500ms between state 1 -> 2 and 2 ->1:

      __HAL_TIM_SET_COMPARE(&htim4,TIM_CHANNEL_1,(uint16_t)900); //INHA PWM Signal ca. 5KHZ
      HAL_GPIO_WritePin(GPIOB,DRV_INLA_Pin, GPIO_PIN_SET); //INLA set High
      HAL_GPIO_WritePin(GPIOB,DRV_INLB_Pin, GPIO_PIN_RESET); //INLB set Low
      HAL_GPIO_TogglePin(GPIOB,DRV_INHB_Pin); //INHB Toggle every 500ms

This is VGHB now in 1xPWM seems to have the correct voltages according to ground but does not have the PWM Signal as expected. Now the the High Mosfet on the B Bridge is turning on correctly.

This is VGHA, PWM signal seems to be applied but is always ON, Mosfet does not go off

As you can see I have very strange behavior.

King Regards,

Nikos

Nikos,

Good to hear!

Could you summarize the questions still ourstanding?

Regards,

-Adam