DRV8873S-Q1EVM: How to start

Hi Piet,

Can we start with what you've already done?  Have you gone through the documentation?

EVM User Guide: https://www.ti.com/lit/slvub68

GUI User Guide: https://www.ti.com/lit/slvubb3

BTW, I deleted two of your duplicate posts.

Regards,
Mike

Dear Michael,

First of all I always reed the (quick) user/operation manuals, because than I have an idea how everything works or must be connected to get a good impression of the product (DRV8873HQ1).

I mention the H version of the chip, because I have no software control (SPI) available in the used processor! 

In the meantime I got the DRV8873S-Q1EVM up and running. There is only one remarkable point and that is: always the error "Open Load Detection" is there. This error should not be there, because the load is always an wired connection. The connection can be in my test environment either an Peltier element (TEC1-12706 or High Power (100 Watt) resistor of 3.2 ohm. Both loads are connected to an power supply of 16V/7A!

The other version I have DRV8873H-Q1EVM is dead!

Best Regards,

Piet

Piet,

I am sorry you are experiencing so many challenges with the DRV8873S-Q1EVM.  It appears you have everything working now with the exception of the open-load protection.  So, please allow me to ask some additional questions to understand this more.

How is the motor connected to the DRV8873S?

Is a single motor connected across OUT1 and OUT2?

When the device exits sleep does nFAULT assert? If so, this is OLP (open-load passive).

Is the fault asserting as the motor is being driven? This is OLA (open-load active).  If so, please provide scope captures of the inputs and outputs. This could be a case where the current is too low to create a voltage greater than Vola when PWM'ing.

Dear Ryan,

first of all is Michael out of the loop???

Some answers: 

No, this is not correct! Both EVM's are dead, but if have the S version (Software controlled (SPI) which I cannot use in my application! No SPI available, but only 2 digital outputs for setting the HBridge!

My application setup:

PSU (16V/7A) =>  TPS259827LEVM (adjusted to 8A) => DRV887H-Q1EVM (controlled by IN1/IN2) => Peltier TEC1-12706.

No motor connected, but an Peltier element connected directly to OUT1 and OUT2 and that's the reason I don't understand the error "Open Load Detection".

Best Regards,

Piet

Piet,

We support the forum as a team, so no, Michael is not out of the loop.

Sorry for my confusion as you said, "got the DRV8873S-Q1EVM up and running".  Now it is dead along with another H variant EVM?  

I was trying to ask questions that would help debug the "open load detection" error, but if the EVM is "dead", will be hard to debug.  

Mike asked in another post.  But can you describe exactly what you mean by "dead"?  Outputs not switching?  What are the symptoms?

Driving a peltier is certainly an application for this device, but we typically suggest a LC filter between the output of the driver and the load to improve the efficiency of the system.  

Dear Ryan,

The situation:

I ordered 3 EVM's from TI knowing:

1. DRV887H-Q1EVM
2. TPS259827LEVM
3. DRV8873S-Q1EVM

1 and 2 I put in test:

• (PSU (16V/7A) =>  TPS259827LEVM (adjusted to 8A) => DRV887H-Q1EVM (controlled by IN1/IN2) => Peltier TEC1-12706) and they where broken (both EVM's) after one night (about 8 hours) running. I reported this situation to TI WEBSHOP and they told me first to make contact with the E2E group.
• Now I am testing/evaluating the DRV8873S-Q1EVM and with this I have the issue "Open Load Detection" at startup. I can clear it after startup and than it disappears!

Questions:

1. Can I send back the 2 broken EVM's and TI will replace them for free or have I to buy 2 new ones (Number: CS0444852)!
2. Can you make the suggestion for the LC filter between the output of the H-Bridge and the Peltier
3. How to send the schematic to you

Best Regards,

Piet

Piet,

1)  Please see the link below.  

https://www.ti.com/info-store/help/returns-refunds-and-cancellations.html

2)  Please see page 9 of the following datasheet for an example calculation.

https://www.ti.com/lit/ds/symlink/drv592.pdf

3) Will contact you over private messaging.

Dear Ryan,

1. I don't want a refund, because i need a new one to do more research using the binary inputs IN1 & IN2 to control the Peltier
2. what's the reason/benefit for using the RC filter between H-Bridge and Peltier
3. Friendship request granted

Best Regards,

Piet

Piet,

1) OK, then you will have to order another one.  Sorry for the trouble.  

2) For the best efficiency, it is best to drive a TEC with a constant current as described in the following app note vs. a PWM that is banging between max. current and zero current.  By adding a LC filter, not RC, you can achieve a nearly constant current as long as you keep the ripple low as discussed in the datasheet I previously sent. 

3) OK, you can then share the schematic privately with me.