• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 47 subscribers
  • Views 437 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

UCC14241-Q1: UCC14241 with UCC21756 protection signal feedback ground issue

Vijaymahantesh Surkod
Intellectual 260 points
Part Number: UCC14241-Q1
Other Parts Discussed in Thread: UCC21756-Q1, TL431, UCC33420

Tool/software:

Hi,

I am using UCC21756-Q1 gate driver IC for driving an SiC MOSFET. The power supply used to generate +15V and -5V for the gate driver is UCC14241-Q1.

The power supply for the gate driver board is received as 24V from the control board which is directly used for the UCC14241-Q1 IC. The 24V input to the UCC14241-Q1 IC has an EMI filter circuit with a common mode choke and differential choke. The input power supply for the UCC21756-Q1 IC is generated by a non-isolated 24V to 5V LDO as shown in the figure.

I have a few questions regarding the architecture.

  1. Can we use the LDO output (5V-DGND) to pull up the ENA (enable) and /PG (power good) pins of UCC14241-Q1 IC? Should a separate circuit be used for the bias voltage (Vbias) as shown in the figure?
  2. The gate driver fault indication signal FLT is fed back to the controller board for protection circuit. This signal is wrt the digital ground (DGND) of the controller board. If we plan to also give /PG also as a feedback signal, can we directly give the signal (/PG) to the control board? Since the /PG signal is wrt GNDP, should a digital isolator be used?

Thank you

  • +1
    TI__Mastermind 30725 points
    1. Can we use the LDO output (5V-DGND) to pull up the ENA (enable) and /PG (power good) pins of UCC14241-Q1 IC? Should a separate circuit be used for the bias voltage (Vbias) as shown in the figure?
      1. Yes, LDO, zener clamp, TL431...any low voltage circuit that can provide TTL 3.3V-5V will work.
    2. The gate driver fault indication signal FLT is fed back to the controller board for protection circuit. This signal is wrt the digital ground (DGND) of the controller board. If we plan to also give /PG also as a feedback signal, can we directly give the signal (/PG) to the control board? Since the /PG signal is wrt GNDP, should a digital isolator be used?
      1. Be careful with the GND definition. If you reference GNDP as DGND and you also have DGND as the return path for 24V, you would have DGND on both sides of L2 (CMC) and essentially be shorting the CMC. For this reason you likely will need a digital isolator

    Regards,

    Steve

  • 0 in reply to Steven Mappus1
    Intellectual 260 points

    Thank you for the clarification. I want a recommendation from Ti about the isolated regulated 1W-2W (24V input to 5V output) DC-DC converter for automotive applications. We estimate the ambient temperature may be from 80 to 100 degrees Celsius. So, do you have a recommendation for such a converter? This converter (24V to 5V 1W converter) will supply all the UCC2176-Q1 (4 numbers to drive an H-Bridge) input side supply and the differential driver and receiver. 

    Thank you

  • +1 in reply to Vijaymahantesh Surkod
    TI__Mastermind 30725 points

    No such isolated integrated transformer device can currently cover such wide voltage conversion as 24V-to-5V. This would require a pre-regulator such as non-isolated buck 24V-to-5V, then UCC34420 isolated 5V-to-5V but note that UCC33420 is only rated to 1.5W max power.

    Steve

  • 0 in reply to Steven Mappus1
    Intellectual 260 points

    Thank you for the reply. I have one more question regarding UCC14241. There is an enable pin which is said to be used for power sequencing. So for driving an H-bridge. Is there any particular order that the power supplies need to be turned on (like bottom mosfets power supplies to be turned one first and then the top ones)?. Or it would be fine if they are turned on at the same time?

  • 0 in reply to Vijaymahantesh Surkod
    TI__Mastermind 30725 points

    These are system level sequencing details you would need to define. Some things I might consider are to monitor /PG from each UCC14241 but also you should monitor RDY from each UCC21756-Q1. When both are in the correct state you know it's safe to begin switching in a controlled manner. If you need additional gate driver support, please submit a new E2E thread with the gate driver part number in the title.

    Steve