Low Noise, Fast H-Bridge

Fatin Haque

Other Parts Discussed in Thread: DRV8837, DRV8835, DRV201, DRV8832

Hi all. I am looking to drive a 15-20Ohm load (with possibly 12uH, 1-10pF) with a current source set at 120mA. This load is a single wire, but there is a nearby identical parallel wire that is independently controlled by another current source (hence why there is also some capacitance and inductance on the load).

I want to switch the direction of this current using an H-bridge with response times within 1's or 10's of ns time frame. This is because the current source response time is within 1msec range (current source is Yokogawa 7651).

The noise should be quite low (say about uA range).

Is there an H-bridge you would recommend or maybe a design that might do the trick (I guess another possibility is to use low noise mosfets or something)?

Thanks!

EDIT: changed nH to uH. Also, added diagram.

over 11 years ago

0 Ryan Kehr over 11 years ago

TI__Guru 55565 points

Fatin,

The closest h-bridge we are going to have is the DRV8835 (dual) or the single channel DRV8837.

http://www.ti.com/product/drv8835

http://www.ti.com/product/drv8837

We have an integrated device that does basically what you are trying to do discretely and that is the DRV201.

http://www.ti.com/product/drv201

0 Fatin Haque over 11 years ago in reply to Ryan Kehr

Prodigy 80 points

Thanks. So, i made a large mistake in my calculations and I think the inductance is actually in the 0.7nH range.

But, I was wondering that these drivers say the rise times are max ~200ns, but since my load is around 20ohms and I plan on only switching from 120mA to -120mA, then can I expect much shorter response times?

I don't think these drivers have spice models, either. So, it would be great to know what you think.

Thanks.

0 Ryan Kehr over 11 years ago in reply to Fatin Haque

TI__Guru 55565 points

Fatin,

Rise/fall times for DRV8837 are typically 100ns with a max. of 150ns as given in the datasheet. Although, I have to be honest and am not sure what the load was under these test conditions and for your load it will surely be different.

The EVMs are $25, so pretty cheap to check out.

http://www.ti.com/tool/drv8837evm

If you need a device in the family with a spice model, the DRV8832 has a model. Scroll down under the MODEL heading:

http://www.ti.com/product/drv8832

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Low Noise, Fast H-Bridge