DRV10983-Q1: Charge Pump Frequency, Open Load Detection

Hello Shinichi,

Apologizes for the delay.

1. What's the switching frequency of charge pump integrated in DRV10983-Q1?
   1. Our charge pump actually swtiches variably long times depending on the load in order to regulate the voltage on our VCP pin to about VCC + 5V (as shown by the DRV10983-Q1 datasheet). The maximum switching frequency is 781.25 kHz.
      
      
2. Can DRV10983-Q1 detect an open load condition?
   
   1. the DRV10983-Q1 can spin motors with a load and without a load. However, I assume you are asking if the DRV10983-Q1 can detect when there is a drastic load change (i.e. load to having no load).
   2. As a result, the DRV10983-Q1 checks for different kinds of event called "locks". A drastic decrease in load will result in increased current out, higher speed, and higher BEMF generated by the motor (as a result of spinning faster). Of our 6 locks, we check for abnormal changes in speed, BEMF, and current which could catch this event.
   3. Note, "drastic" is the key word here because small changes in load (i.e. air intake is partially covered) because these are normal events in certain applications. As a result, further evaluation on the exact senario would be needed.

Best,

-Cole

edit: corrected switching frequency

Hello Shinichi,

I understand now, thank you for the explaination. Yes, Lock 3 is the no motor fault. The Hi-Z condition would result in no current flowing through the phases of the device (and motor) which the device can detect and stop trying to drive the non-existent motor.

Best,
-Cole

Hey Shinichi,

I would like to start that I gave some misinformation about our chargepump frequency earlier. I have editted that message to correctly reflect this new information.

Anyways, I would like to say again that our charge pump switches variably depending on the "load" in order to regulate the voltage on VCP. This load comes from the DRV10983-Q1's demand for charge in HS predriver and Buck converter. Specifically, our device will detect a voltage level on VCP and determine the need to pump up the voltage. In other words, VCP will fall below some threshold, the charge pump will turn on, switching in some square wave like fashion until the voltage on VCP passes some threshold. The switching looks a bit square waves and can be observed on CPP and CPN.

What this means, is that the device will switch more when spinning a motor compared to an idle state because the demand for charge is higher (i.e. High side FETs need to be driven). This also mean that the charge pump activity heavily correlates to the system. For example, VCC level and motor speed will change the "load" in the system. This means it is not possible to tell you what the min switching frequency will be in the idle state or spinning motor state. An exmaple picture is shown below:

However, the maximum charge pump switching frequency is 781.25 kHz (sorry for the misinformation earlier). That means if the VCP was continually below the threshold, the square wave switching would occur 100% of the time at 781.25kHz. If we are putting this in context of EMI, I expect to see a peak at 781.25 kHz with lower Quasi-peak values (because it is not switching all the time).

Best,

-Cole