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ADuM3220 driving H-bridge N-mosfet

DDer
on Jan 21, 2014

Hi,

I am having problem when driving my half bridge of N-mosfet using ADuM3220. Hope to have advice from here.

I would like to ask whether:

- Is there any problem with the circuit?

- Is it a must to add a diode between the gate and source of the MOSFET?

- During testing, my output (load + or load -) is clipped at the my gate voltages instead of my bridge voltage, why is this so?

- There are times, my gate driver was damaged with output latch high, is there any way to mitigate it?

- Can I use 1 ADuM3220 to drive half bridge?

Detail of the circuit:

No load is connected yet.

Input driver voltage = 5V

Output driver voltage = 12V

Bridge voltage = 75V

Switching frequency = 50kHz and 400kHz (tried there 2 frequencies)

1A = signal 1

1B = inverted 1A

2A = signal 2

2B = inverted 2A

Previously, I have successfully used a separate opto-couplers and gate drivers to drive the bridge and was hoping that the smaller form factor of ADuM3220 can improve my circuitry.

Thanks.

  • 0
    •  Analog Employees 
    on Jan 21, 2014 10:38 PM over 7 years ago

    Hello DDer,

    The ADuM3220 has two outputs that share a common ground on the secondary side. This means that unless there are very specific conditions, it is not best suited for driving a half-bridge configuration. The reason for this is that the high side channel must be able to follow the high-side FET up to the bridge voltage when the low-side switch is turned off.

    Please look into the ADuM3223, ADuM4223, or the ADuM7223 for a half-bridge driver solution. These chips provide two separate grounds for the two separate output channels. One consideration that you must make is that the high-side channel has to be powered independently from the low-side channel. If your operating frequency and duty cycle are sufficient, a bootstrap configuration is usually the easiest and cheapest solution. The datasheets for these parts covers bootstrap operation.

    Here is an application note about using the ADuM3220 to drive an H-bridge, but please note that the different channels of the two ADuM3220's are set to different sides of the H bridge. This allows their grounds to be at the same potential while they are driving their respective gates. It is suggested that you use a device designed to be used in a single leg of a half-bridge.

    http://www.analog.com/static/imported-files/tech_articles/Inside_iCoupler_Technology_Driving_an_H_Bridge.pdf

    If you are in a rush, and cost isn't your concern, since you probably have many ADuM3220's on hand, you could also dedicate an entire IC to the high-side, and another to the low-side. Just remember to power the high-side with some sort of floating supply, like a bootstrap or another isolated supply.

    Let me know if you have any more questions,

    RSchnell

  • 0
    •  Analog Employees 
    on Aug 2, 2018 2:33 PM over 2 years ago
    This question has been assumed as answered either offline via email or with a multi-part answer. This question has now been closed out. If you have an inquiry related to this topic please post a new question in the applicable product forum.

    Thank you,
    EZ Admin