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UCC27284: Gate driver damage

Miteshkumar Dalabhai Patel
Intellectual 2410 points
Part Number: UCC27284
Other Parts Discussed in Thread: UCC27211A

Tool/software:

Hi Team,

One of my customer is using UCC28284DRMR for their new project called Solar Optimizer.  They have made 50 boards & out of 50 boards, 20 boards has gate driver failure.

We measured below impedance on each pin w.r.t pin 7. In Most of the cases Pin 2 gets damage & also affecting impedance of pin 1, 3 & 4 as well. Low side gate driver looks ok but not sure for the same.

 

OK IC - Fresh

Faulty 1

Faulty 2

Faulty 3

Reference Pin

7

7

7

7

1

138.5K

1.8K

125K

1.8K

2

7.75M

1 Ohm

1 Ohm

1 Ohm

3

9.5M

725K

1.1M

1M

4

9.2M

710K

930K

890K

5

7.9M

10.76M

9.2M

10.36M

6

8.5M

10.1M

9.6M

9.5M

7

0K

0K

0K

0K

8

121K

130K

102K

130K

Circuit works up to 40V input (configuration  - Sync Buck). Whenever they tried to icrease voltage beyond 45V, circuits works for 20 to 30 seconds & after that driver seemlessy fails & we don't know the reason. for the same. Duty cycle in most cases is 98.7% so majority time high side driver is on & very small time low side gate driver is on. After failure we observed that even low side gate driver is also no apperaring at output however impedance number looks ok for good device & damaged device.

After this we added small resistor (2.5 ohms) inseries & found that boards are working for 52V inputs as well after replacing the devices. But we are not confident if these boards will work or not. Out of 50 boards 30 boards without adding resistor with boot cap are also working for 52V input as well & hence we are not drawing any conclusion that solution of adding 2.5 ohms is solving issue or not. Customer will make another 20 boards with series resistor with boot cap & if all board survies then we can be sure that solution provided is ok for the long term.

We would like to know that why HB pin showing sort with ground? What could be the reason for failure of Pin 2? Is it -ve spike or voltage crossing absolute max. on pin 2? We haven't observed any of these two while testing.

Pls. help & share your inputs.

Regards,

Mitesh

  • 0
    TI__Expert 8460 points

    Hi Mitesh,

    Can you share the schematic and layout? Can you also share the system characteristics (VDD, frequency, load)? For a sync buck application, it sounds like a high current driver would benefit here. I would recommend looking into the UCC27211A.

    Thanks,
    Rubas

  • 0 in reply to Rubas Khalid
    TI__Intellectual 2410 points

    Hi Rubas,

    Thanks for responding qucikly.

    We can discuss about UCC27211A & they have common foot print so moving forward they can be able to test the same with existing PCB.

    They will not be able to share schematic & layout but we have gone through the schemtaic & layoput, we can say that it is not completly off from shcemtaic & layout prospective.

    Starange part is some boards are working & some are not working. After adding the resistor with BOOT cap we haven't observed any failure  & hence we want to know pointer about the failure.

    What could be the reason & why adding small resistor in series to BOOT cap resolving our issue?

    We are trying to arrange layout & schematic from their management side but  not sure at this moment.

    Thanks

    Mitesh

  • 0 in reply to Miteshkumar Dalabhai Patel
    TI__Expert 8460 points

    Hi Mitesh,

    It may be that the average current for the boot diode is reaching high levels. We recommend to keep the average current below 80mA; the average current can be found by using the switching frequency (fsw) and the total charge (Qg) of the high-side FET connected to the HO pin: 

    Iavg = fsw * Qg

    Here is our application note covering bootstrap circuitry design: https://www.ti.com/lit/an/slua887a/slua887a.pdf

    Thanks,
    Rubas